As I have said countless times on here Charles, I am "mostly" an HVAC repair contractor.

Ray,

If you are doing mostly repairs, and few new installations, then why do you harp on the topic of doing a load calcualtion? We realize your customers in Katy, Texas think a 5 ton AC condenser is the right size. Installation of new HVAC equipment has become very exensive. I feel the HVAC contractor should spend the time to determine if smaller equipment is appropriate.

We can't assume the original builder's HVAC contractor installed the correct size. The load calculation is one of the tools HVAC professionals use for best installation of their customers. Used correctly it has the potential to save the customer money.

"AAC: You can't really upsize or downsize an Air Conditioner in which the furnace / and duct work are to support the already existing AC size."

I tried to convince the two contractors from which I asked for quotes on replacing my system that eighteen years of experience in this house tells me that I don't need 5 tons. They both said "Five tons is what you have, five tons is what you need." The best I could do at a reasonable up-cost is get a two-stage (3.5 tons on low, 5 tons on high, as I understand). The installing contractor didn't change anything about the ductwork. It runs at low stage 99% of the time during the heat of the summers since it was installed in January 2022 (setpoint 78°F the first couple years, 77°F in 2025). It cycles between low and high in heating when the ambient dips below 30°F but the auxiliary doesn't run except during defrost (setpoint 69°F).

How is it that the system works running at low speed (the blower speed reduces accordingly), but a single-stage 3.5 ton or 4 ton system would be unable to function?

" How is it that the system works running at low speed (the blower speed reduces accordingly), but a single-stage 3.5 ton or 4 ton system would be unable to function? "

Either because of the contractor's ignorance (whether real or pretend) or incompetence. Likely a little of both.

I don't know why you would engage a contractor who wouldn't listen to what you wanted. I wouldn't have.

My second place is a poorly insulated 1500 sq ft plus some structure in a development, in a warm and sunny coastal location. The load calc for cooling came out a bit over 2.5 tons. In talking it over with the contractor, I asked what he thought. He said something to the effect of "most contractors would round up to 3 tons, but if this were my home, I'd put in a 2 tonner". So that's what was done. It works great. It provides great comfort and consistent temperatures.

Good thing I'm not in Katy Texas. The conversation would have never happened.

"The load calculation is one of the tools HVAC professionals use for best installation of their customers. Used correctly it has the potential to save the customer money." Indeed. A load calculation has the potential to reduce the initial (or system replacement) cost, the system operating cost, and to improve occupant comfort, too. Although Ray doesn't do load calcs and operates only in municipalities which don't require permits and inspections, the Texas Dept. of Licensing and Professional Regulation requires load calculations because they're required by the International Mechanical Code (M1401.3,) which Texas adopted. The TDLR publishes a helpful flyer on the subject which you can peruse by clicking on the following link:

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.tdlr.texas.gov/media/pdf/Consumer%20Protection%20-%20ACR%202.pdf

The following text is excerpted from the flyer:

"When a contractor is bidding to do work for me, what should they do?

● They should inspect your HVAC system before beginning repairs.

● They should perform a heatload study.

● They should do a duct work study.

● They should specify the makes and models of the equipment, including model numbers, names, quantity, manufacturer warranties, documentation, and energy ratings.

● They should provide bids or estimates in writing.

● They should leave all the owner’s manuals, documentation of installation procedures, AHRI certificate, and any records of measurements and testing."

Ah, Houston we have a problem....

No where have I ever said I don't do heat load calculations. (that is a myth in the builders head that couldn't do the heat load calc right the very first time -- when the house was built.)

What I have said: I don't do them for FREE.

If I am going to do one, there are requirements. Most of the time upwards of 95% of the time I am repairing an Air Conditioner.

Only a PE shrill is going to come to a broken AC and say hey we need to do a load calc to see if this AC unit is the right size or not and then proceed to say you need a more often than not bigger not smaller AC. (PE? = Private Equity, not engineer)

I'm more likely to: repair it, if possible. (you don't need a heat load at that point to do that)

If you want a heat load performed: Tell me in advance I'll come to your house and tell you what the cost will be to do so.

Prices differ from one house to another, if you have multiple units I require the heat load to be for the whole house, not just the area of concern in which one unit is serving.

Permits and inspections do not check or do a heat load calc to prove the one being done is accurate or not. (PSST: This very thread proves it -- and the area in question is NOT Katy, Texas -- it's Ohio)

Try and make it make sense. Good luck. Fun, fun, fun.

---------------

Ray,

If you are doing mostly repairs, and few new installations, then why do you harp on the topic of doing a load calcualtion?

Everyone loves a good argument and there's is plenty to argue about in the realm of heat load calculations. After doing 1000's of them in my early career I could see they aren't always what they are cracked up to be... we'll give you a total (of that) can be easily skewed one way or another... then to be exact "you know best practices" yada, yada, yada --- the total it gives you the equipment doesn't match up so you either then round down or round up.

If you get to 60,000 BTU's most 5 ton AC's don't even hit the 60,000 btu threshold. Most of the time at best "these days" it's around 57,000 BTU's -- some may not even hit 53,000 BTU's. (yet these are considered 5 tons, not 4.5)

The only way you're likely to hit those values is Inverter like the Bosch Bova 2.0 at that upper end, but the Bosch works in such a way, that it will never deliver 60K BTU if that isn't needed via an assorment of proprietary algorithms in which the unit makes ramping decisions.

The importance of a heat load is mostly in the realm of preventing mold growth, as an air conditioner for my area in particular (very humid area more often than not) a larger over sized air conditioner will not run long enough to remove humidity. It will for the lack of better terms, bang on and bang off.

Humidity removal via an air conditioner is not the primary goal. Air conditioners are designed to lower temp, not focus on dehumidification. Even a Bosch Inverter has it's limitations, it does not "control" humidity. Trying to dehumidify with an air conditioner more often than not results in over cooling, to the point you're too cold.

Adding a dehumidifier, you just upped your overall cost and your electric bill will also go up too. Some people are sensitive (especially in a hotter climate like mine) if the dehumidifier is running will spit out 90F air (with the AC cycled off)

In some instances a home's best fit may be to do actually that if "control" of humidity is important. Most of the time the cost, the possible heat sensitivities, maintenance and ultimately the replacement of such systems should be weighed?

Just arguing over sizing alone is a very small metric in the grand scheme of things, But as we have proven with this thread... it's a good argument and people LOVE to argue.

I don't care what we talk about here as long as it's about HVAC --- doesn't matter to me. It's what I do. (If you don't like how I do it? Don't care about that either, nothing you have said or done for over 10 years I've been posting here has done anything to my world in Katy, Texas -- because I have a slew of customers that initially was around the West Side H-town area, but eventually Katy took over. You go where the business is.

So the thought that I only service areas that don't require permits? it's laughable just as much as anything else a builder is going to talk about all the while and intentionally saying he doesn't do the heat load calc correctly either. It was wrong from the day the foundation was laid, isn't that right Charles?

So much fun. I love HVAC. I let you decide what we're going to talk about.

HVAC has never been a 1 size fits all market.

Ray,

There's enough evidence in past threads here on houzz.com that any load calculation you perform and the associated equipment sizing wouldn't be worth the cost of the paper it's printed on. Here's one such example:

https://www.houzz.com/discussions/6480904/how-do-i-know-if-my-house-hvac-is-sized-correctly

Charles, same old dog no new tricks.

Nothing has changed since then... look this thread we are in proves it again you don't need to look backwards.

and this time it's Ohio.

Again, Charles is telling you he didn't get the heat load calc right either since the day the foundation was laid.

The builders are known for being the biggest smoke screen blowers there are in the housing market. Charles should focus on his own work?

Houzz.com forums are open to home owners, builders, remodelers and trade professionals alike. This thread isn't about homebuilders, Ray. It's about HVAC equipment sizing.

My 18-year engineering career involved a lot of HVACR work (design, installation, operation, and maintenance) of commercial and industrial systems for a major food manufacturer. Along the way I earned a P.E. license. Those experiences have served me well as a custom homebuilder and remodeler collaborating with my trade partners to deliver better performing homes. While my clients hold me accountable for their comfort and the performance of their homes, it's my HVAC contractor who is responsible for design of the HVAC systems and who pulls the mechanical permit and is subject to inspection. He's well qualified for task. We appreciate collaborating with each other on design and performance of HVAC systems which is why he's been my exclusive HVAC partner for the past 20 years. You might follow his example. Your clients would certainly benefit.

"AAC: Seems to me we had a conversation on this board and I tried to sell you on the idea of the Bosch BOVA 2.0 -- steps in cooling 1% up and down... yet it also seems to me you were hung up on the Trane brand. The Bosch BOVA 2.0 could have given you even better -- put the sizing guessing game to bed. (But Bosch is premium equipment so cost also entered the fray)"

My question above isn't regards to the virtues of this brand vs. that or variable-speed vs. other. It's why does a two-speed system running on low/3.5 tons work nicely on the same ductwork which was designed for 5 tons and that (your words) won't work for a single-speed 3.5 ton (or 3 ton or 4 ton) system? If the 5-ton ductwork won't work for a smaller-than-5-ton system, then how can it possibly work for a Bosch BOVA 2.0 that's throttled down by 80% of capacity, or whatever?

Also, when I do a search at Bosch HVAC website for a dealer within 200 mi of Katy TX, the result shows one, in Lufkin?

I have installed all sizes from 2 ton to 5 ton, there is very little difference in cost from 2 ton to 3 ton. Cost from 4 ton to 5 ton: again very little difference.

Ray,

I have not shopped for AC condensers recently, but given the big increases in HVAC equipment during the past few year you will have to forgive me if I am a little skeptical with your response.

Can you provide what would be the price difference to install a 3 ton verusus a 4 ton AC condensers in Katy, Texas? Let's narrow it down to a Goodman 2-stage condenser, a brand I believe your distributor supplies and uses your prefered R-32 refrigerant. You can pick the model numbers for this excercise.

The cost difference in the equipment is not a relevant consideration. The heat gain/loss data is what matters, assuming cooperative duct sizing. And since usually the REAL analysis usually determines, not surprisingly, that the existing equipment is too large, duct sizing problems, if any, are remedied.

Ray, do you buy your shoes two sizes too big because they're the same price as the right size? How about pants?

Charles/Ray: I take it you two are long retired or I don't know how you'd have the time to type such long rebuttals to each other?

sktn, I don't know if you caught the following comment from Ray:

" you know areas like where Mr. Fudd lives where he can afford to wait for 6 weeks for someone to come and change out his equipment because he believes waiting long periods in discomfort is the tried an true formula for getting quality work. "

The background to this was some years ago, in a civil exchange, I told him that when I chose the winning proposals (highly recommended contractors, two different jobs, three systems in total in two different locations, the ones chosen were not the cheapest ones), that both contractors were extremely busy and working off install backlog schedules. Both had split teams, those who answered repair and emergency calls, and others to do installs. One wait was 4 weeks, one was 6, which was fine with me and presented no problems at all. He was flummoxed,

I've told him many times that the proposals related to functioning installs that I wanted to proactively replace, that the proposals took place in winter with the waiting periods in the Spring/early Summer, and so neither inconvenience nor discomfort were involved, but that's never registered with him.

I suspect he'd never heard of HVAC contractors so successful and so busy as to have weeks-long backlog schedules. And perhaps that's not his reality. All the good ones in my area do and I suspect the same is true in most places. Some even decline bidding at times because they want to work down their backlogs before taking on more work. Perhaps he starts most weeks with a mostly open schedule and waits for the phone to ring.

Long way around to say to your comment - he seems to have plenty of time.

sktn77a,

Houzzers expect and deserve accurate information from professionals. When they get self aggrandizement in lieu of factual content you can bet I'll take the time to push back whether I'm retired or not (and I'm not.)

Charles Ross Homes: it's my HVAC contractor who is responsible for design of the HVAC systems and who pulls the mechanical permit and is subject to inspection.

According to following the "best practices" the heat load calculation is wrong before the foundation finishes curing. But we won't know this until 25 years later. (according to the very thread we are in.) No, this is "best practice".

It's still the same result if you're going to just follow the mantra. No one is ever right. That is what we are supposed to believe?

Houzzzers expect and deserve accuatate information: Charles according to you own metric it's not accurate... well around these parts we give approximations -- you said it yourself in this very thread. --- that is not accuracy.

If I was wrong to challenge the system? The OP of this very thread would have gotten all identical bids --- but none of them were the same including offering a system in the current tonnage the home has had for 25 years. --- it's been wrong for 25 years! Oh well it's good now that we know it was wrong? --- This is your best practice in action. This thread proves it.

Dadoes: My question above isn't regards to the virtues of this brand vs. that or variable-speed vs. other. It's why does a two-speed system running on low/3.5 tons work nicely on the same ductwork which was designed for 5 tons and that (your words) won't work for a single-speed 3.5 ton (or 3 ton or 4 ton) system? If the 5-ton ductwork won't work for a smaller-than-5-ton system, then how can it possibly work for a Bosch BOVA 2.0 that's throttled down by 80% of capacity, or whatever?

Reduction of humidity or certain people like a different temperature. What is comfortable to you may not be comfortable to someone else. See all of you talk about what is comfortable to you? Yeah what you know as comfort? What is comfort really?

Not to hot, not too cold... just right. So how do you explain vanilla vs chocolate vs strawberry as to which is best to someone who has not had any of those flavors and the entry to those flavors is $1000's of dollars. Let's baffle them with BS. But we already know the flavor of BS, because that is free and on display everywhere.

In terms of there being no contractor for Bosch near where you live? I only talk about things that are in my control, not out of them. There is no perfect option when it comes to HVAC. I don't have to point you far to prove that, you're in neck deep in this thread. LOL.

Different opinions don't bother me as much as they do the 3 or 4 of you. There's far differing opinions in the beyond outside the reaches of Houzz.

------------

sktn77a

13 hours ago

Charles/Ray: I take it you two are long retired or I don't know how you'd have the time to type such long rebuttals to each other?

I took typing class in high school so it's not what I would call difficult to bang out a long winded reply. I can't speak for Charles... but I'm merely filling in my morning drinking coffee time coming here of a morning before I start my day.

I might spend 30 minutes here most days.... not long. Now if you can't type -- yeah I'd probably be in here up until noon typing out some of these posts. (More myths in the heads of people I touched on a few posts up) .

----------------

Mr Fudd: The background to this was some years ago, in a civil exchange, I told him that when I chose the winning proposals (highly recommended contractors, two different jobs, three systems in total in two different locations, the ones chosen were not the cheapest ones), He was flummoxed,

Yeah I am so flummoxed I keep mentioning it over and over and over again. This is being flummoxed. There's a not so cheap contractor here in H-town that will come to you for free, they get busy too... they have got probably more than 30 install crews. Probably won't have to wait for 6 weeks though. LOL. This is comfort too. What 1 finds comfortable others will not.

Yeah, I'm flummoxed. again more myths. We'll spin everything every which way to say we're accurate all the while by being inaccurate. Comfort. How do you define it?

The cost difference in the equipment is not a relevant consideration. The heat gain/loss data is what matters, assuming cooperative duct sizing. And since usually the REAL analysis usually determines, not surprisingly, that the existing equipment is too large, duct sizing problems, if any, are remedied.

Again there is very little cost difference from say 2 ton to 3 ton or 4 ton to 5 ton even smaller difference in price from 2 ton to 2.5 ton or 3 ton to 3.5 ton. Most of the time it might be a few hundred dollars.

This however does not negate the sizing conundrum as to which is accurate. The measure to being accurate here is again to guess. Well some one took the time to measure so that guess must be more valuable to choose from. Sure, you can go with that theory but in my experience it's used as a metric to often times dupe you.

How? My climate furnaces last a long time here. The easiest way to get a whole system change out would be how? Tell some one they have the wrong size. Congratulations.

No one is going to double check that work. Even if you live in an area in which permits are pulled.

You'll have those that argue and say this is the right way according to best practices and they'd be right... but? You won't know if you're getting hoodwinked all the while following the so called "best practices" mantra.

Now if you disagree with my profound wisdom... you can't just say I'm flummoxed.

I'm fine with that. LOL.

----------------------

Mike home

Ray,

I have not shopped for AC condensers recently, but given the big increases in HVAC equipment during the past few year you will have to forgive me if I am a little skeptical with your response.

Can you provide what would be the price difference to install a 3 ton verusus a 4 ton AC condensers in Katy, Texas? Let's narrow it down to a Goodman 2-stage condenser, a brand I believe your distributor supplies and uses your prefered R-32 refrigerant. You can pick the model numbers for this excercise.

It's my opinion that if you're wanting 2 stage equipment the better value is Inverter, such as the Bosch BOVA 2.0 (although there are new gotchyas if you decide that way now) Now the cost diffences between those options (Inverter and 2 stage) blur and inverter is the far and away better value, in my opinion. (you only get my opinion from me, I'm not even influenced by those on this board. )

So while I do sell Goodman equipment it is not the only choice but with refrigerant changes and such an AC install going forward will be "at least" a Condenser and a Coil & mitigation controls. The mitigation costs are the same no matter which size. ( I mention this because the video shows me only changing a condenser, due to flammability of newer A2L refrigerants this is no longer possible to do a condenser change only.)

The difference is the cost of the equipment --- this difference from 3 ton to 4 ton in single stage configuration R32 is that the 4 ton equipment is $500 more. This doesn't give you the entire costs of the job because those costs can vary some and prices change all the time. But typically a $500 difference is almost always right a jump from 3 ton to 3.5 ton might be $200 or $300.

BUT to decide which the 3 ton or the 4 ton? If your furnace does not support a 4 ton, I am not going to quote a 4 ton. Because it won't work, this is a hot climate here we run our AC's 10 months of the year here.

---- to get into 2 stage you're really in rip it all out and start over because 2 stage systems were largely to be sold as complete systems. The Bosch Inverter doesn't require a full system change out, that perfectly good furnace can be used with the Bosch Inverter. Each climate area is unique with it's own set of challenges. This example shows though how the Bosch Inverter "premium equipment" can give you better value than a merely 2 speed vs upwards of 60+ speeds depending on configuration and sizing of the machine.

-------

It's 6:30 am.

It's my opinion that if you're wanting 2 stage equipment the better value is Inverter, such as the Bosch BOVA 2.0 (although there are new gotchyas if you decide that way now)

Ray,

You have stated in the past your customers have 90%+ gas furnaces. Selling them an inverter type heat pump could be a hard sell. In climates where temperatures are much colder than in the winter than Katy, Texas most homeowners will want to keep their gas furnace. If there are "gotchyas" then this could be an additional reason why a homeowner may not switch to a Bosch BOVA 2.0 for heating.

The difference is the cost of the equipment --- this difference from 3 ton to 4 ton in single stage configuration R32 is that the 4 ton equipment is $500 more. This doesn't give you the entire costs of the job because those costs can vary some and prices change all the time.

I am not a HVAC contractor, so I could be incorrect in what I am about to state. It is my understanding is that HVAC contractor will typically determine the labor cost based the equipment cost. For example a 4 ton condenser which may cost an additional $500 could result in a $1000 extra cost to the customer if the contractor is using a 50% mark up on equipment costs.

BUT to decide which the 3 ton or the 4 ton? If your furnace does not support a 4 ton, I am not going to quote a 4 ton.

No argument here. The idea I would like you to appreciate is the load calculation may allow a homeowner to reduce the size of the equipment. Consider a homeowner in a climate in the Northeast where summers can be hot and winters are cold, The customer has a 25 year old 4 ton 2-stage condenser which needs to be replaced paired to an 80K BTU 90% AFUE furnace. The customer wants all new equipment and would like to replace it with a 3 ton 2-stage AC with a 60K BTU 95% AFUE furnace to try to save money on the installation costs. Does the contractor say no the builder sized it correctly and that is what will be installed or take a guess based on some rule of thumb and reduce the size the equipment? Larger equipment means the contractor makes more profit, smaller equipment means the homeowner saves money. I think the homeowner would agree to pay for a load calculation if there is an opportunity to save $1000+ in installation costs.

" The measure to being accurate here is again to guess. "

Who wants a contractor of any kind with this attitude? This says it all.

Ray,

You have stated in the past your customers have 90%+ gas furnaces. Selling them an inverter type heat pump could be a hard sell. In climates where temperatures are much colder than in the winter than Katy, Texas most homeowners will want to keep their gas furnace. If there are "gotchyas" then this could be an additional reason why a homeowner may not switch to a Bosch BOVA 2.0 for heating.

Mike home --- wrong. Most of my customers have 80% gas furnaces (non-condensing) -- a few have condensing furnaces because that is what the builder installed.

Bosch is a Heat Pump. Yes, but configuration wise the heat pump part of it is not used as a heat pump except for my house which has electric heat. It's simply configured to run as an Inverter AC.

The "gotchyas" right now are related to the type of A2L refrigerant Bosch decided to use which I have said many times already (R454b is not a good choice in my opinion)

--------

It is my understanding is that HVAC contractor will typically determine the labor cost based the equipment cost. For example a 4 ton condenser which may cost an additional $500 could result in a $1000 extra cost

I provide choices but those choices do not range from 3 ton choice versus 4 ton choice. If the unit is a 3 ton all the choices will be 3 ton. If the customer has displayed signs of trauma in terms of price the choices are often times limited due to that. I am not going to waste my time offering something I know some one can not afford.

Like the Bosch, it doesn't fit every situation... just as much a Goodman single speed or Grand Aire single speed does not fit every situation. Some times I will offer a Grand Aire over the Goodman and sometimes mix and match with offers of the Bosch. I don't win every bid but I don't care I am primarily an AC repair man. While equipment comes with that it is far and away not no where near the main focus.

Some companies do? I am not some company, I am Austin Air Companie. I don't really care what other companies do. Why should I?

If there is a need for AC / the furnace is rated for 3 tons of AC -- the quote is going to be for 3 ton because that is what the furnace can support. --- Well we need to run the calc maybe it comes to 4 tons? then we can charge far more than the $1000 Mike Home is talking about because now we might be replacing a 12-15 year old perfectly good furnace.

This was the exact situation I came across except it was a 3 1/2 ton AC. The so called busy expensive guys were called before me -- they were trying to convince the home owner that a 5.5 year old home the builder installed the wrong size and it all needed to be ripped out.

They didn't believe the rhetoric, called me --- I repaired the unit. --- Repaired it several more times after that typically 2 years apart from one another. Repeatable fix it once people call you over and over.

Again my focus is to fix it. BUT, that isn't always possible OR it may be in the best interest of the customer to move on to new equipment. Wasting money (that really isn't your own?) If a customer feels like their money is being wasted? what happens? ( I already know )

No argument here. The idea I would like you to appreciate is the load calculation may allow a homeowner to reduce the size of the equipment. Consider a homeowner in a climate in the Northeast where summers can be hot and winters are cold, The customer has a 25 year old 4 ton 2-stage condenser which needs to be replaced paired to an 80K BTU 90% AFUE furnace. The customer wants all new equipment and would like to replace it with a 3 ton 2-stage AC with a 60K BTU 95% AFUE furnace to try to save money on the installation costs. Does the contractor say no the builder sized it correctly and that is what will be installed or take a guess based on some rule of thumb and reduce the size the equipment? Larger equipment means the contractor makes more profit, smaller equipment means the homeowner saves money. I think the homeowner would agree to pay for a load calculation if there is an opportunity to save $1000+ in installation costs.

It largely is a myth that a larger system makes more profit for the contractor. It's the same amount of work unless you only change out "some of the equipment" versus all of it. Most of the time people tell me they want bigger... and I have to explain to them, just as much as or more than I have to tell you (mike home) that is not how it works.

You can't rob peter to pay paul or rob paul to pay peter. If the home is in some other climate? Well I don't service those climates. Heating season is here one day gone the next. We're using heat right now, but well be back again to AC by the end of the week. So why would I think about what happens in other climates?

To that end... a 3 ton complete vs 4 ton complete (single stage everything basic 80% gas, single stage AC -- the difference between those two sizes might be $600 if that. It will take the same amount of labor to install them no matter. If a company chooses to charge more than that $600? Anything is possible.

But if you don't need a new furnace? a furnace by itself is far greater than $1000 difference. If you need a furnace, then you need one and gotta pay for it.

If a home was built and a 3.5 ton system has heated and cooled that home for 25 years with no complaints of the system not keeping up / electric bills / gas bills reasonable -- how do you reach those conclusions? Simple really. Use an Air conditioning repair man -- if he repairs it and it functions fine with no outstanding issues in terms of keeping up -- what better argument is there to suggest the system is "properly sized".

Honestly a 1/2 ton upsize or down size is not going to make that big of a difference on the AC side of things for a 3 month AC use climate like Ohio or even on the northern east coast of the US for that matter. The down size may cause issues for keeping up on the heating side. So all of this leads to more arguing in my opinon. A half ton less for a hot 10 month use climate? Depends on the comfort level someone wants -- if 78-80 in the summer is what you can live with, sure a smaller AC might be all you need. That isn't the norm, I would sweat bullets at 78-80F. (our design temp is 75F indoor / 95F outdoor-- alot of people want it cooler than 75F yes, well smaller AC is not likely to hit that in the dead heat of summer July thru August and sometimes some of September)

A 25 year track record is a long time to prove something as being accurate. It appears the mechanic for doing a heat load calc is only when the system breaks and the need for a new system comes into play.

If the system was 5 years old / not keeping up or too much heat / too much cooling?

In my experience these kinds of things are attributed to something that is broken. At this day and age I can't tell you how many times I've repaired them. I have had people call me that question me about the unit being too small. Um yeah.

I fix it -- and? crickets. (alot of times these sorts of things are refrigerant related problems - lack of refrigerant is a capacity problem 9 times out of 10.) Certainly that is not always the case. I did find one years ago in which the 5 ton furnace was changed out for a 4 ton, not by me but a home warranty company. -- I told them I am not going to fix the AC until they get a properly sized furnace that can support a 5 ton AC. I could make this up, but I am not. Big Shocker! Yeah I've seen too much at this point.

• 
  Elmer J Fudd11 hours ago" The measure to being accurate here is again to guess. "
  Who wants a contractor of any kind with this attitude? This says it all.

Choices are good? We know what? Mandates are bad.

Oh well California has a mandate on? all of it. ~ You live where you live, I live where I live. Freedom doesn't knock, it rings!

---------

It's 5:53 am

"(our design temp is 75F indoor / 95F outdoor-" No they are not. The 97 1/2% outdoor design temperatures for Houston, TX are 94F d.b./ 79F w.b. summer, and 32F winter. You can find the design temperatures in the 2021 International Plumbing Code, Appendix D. You need the wet bulb temperature as an input to calculate the total load-- which includes both the sensible and latent (dehumidification) loads. More evidence to make any load calculation you perform suspect, Ray.

Ray,

Below are some comments to your last post.

Most of my customers have 80% gas furnaces (non-condensing) -- a few have condensing furnaces because that is what the builder installed.

What I meant to write, but did not do a good job, was 90%+ of the population of your customers in Katy, Texas use gas furnaces for heating. It makes sense in a mild winter climate most furnaces would have an 80% AFUE rating.

Bosch is a Heat Pump. Yes, but configuration wise the heat pump part of it is not used as a heat pump except for my house which has electric heat. It's simply configured to run as an Inverter AC.

It seems wasteful to pay for inverter heat pump and then only use it in cooling mode. I would think it would cost less to install an inverter type AC condenser but perhaps this may not be true in the Katy, Texas market.

If there is a need for AC / the furnace is rated for 3 tons of AC -- the quote is going to be for 3 ton because that is what the furnace can support. --- Well we need to run the calc maybe it comes to 4 tons? then we can charge far more than the $1000 Mike Home is talking about because now we might be replacing a 12-15 year old perfectly good furnace.

Ray you have reversed the example I described. In my example the customer has a 4 ton AC paired with an 80K BTU furnace. It is 25 years old and is a candidate for a full replacement. The contractor quotes the same size. Customer asks is it possible the equipment is over sized and if it can be replaced with a 3 ton AC and 60K BTU furnace so to save money on the installation costs. I don't know where you picked up I suggested replacing a 12-15 old perfectly good furnace.

It largely is a myth that a larger system makes more profit for the contractor.

It is not a myth in markets outside of Katy Texas. I have seen it with actual quotes of the same equipment with different sizes. You should be able to find training videos on how to price the installation costs of HVAC equipment explaining how HVAC contractors price installation costs.

If the home is in some other climate? Well I don't service those climates. Heating season is here one day gone the next. We're using heat right now, but well be back again to AC by the end of the week. So why would I think about what happens in other climates?

Most of the posters of this forum asking for advice about replacing their furnaces, air conditioners, and heat pumps don't live in the climates like Katy, Texas. So the advice you provide as a 30 year HVAC professional has to be taken into account for those other climates. Your specialty is repairing air conditioners quickly in a cost effective manner. You don't do many new equipment replacements, but could certainly do one if required.

You disparage performing a heating and cooling calculation whenever it is mentioned. I am not sure why if most your business is doing repairs. However when people come to this forum asking for advice about spending $15K - $20K on new HVAC equipment you don't think doing a load calculation has any value due to the reasons you have stated in the past. Equipment and installation costs in markets outside Katy Texas have increased significantly during the past 5 years. It only seems right a HVAC professional such as yourself would advise an uneducated homeowner there are tools available to help make good equipment choices. The biggest myth is in all of this is the builder always installs the correctly sized equipment. I know this myth was not true when I replaced three furnaces and three AC condensers in my house.

"The biggest myth is in all of this is the builder always installs the correctly sized equipment." Builders have never had an incentive to install larger, more expensive HVAC equipment than is necessary to meet code requirements or project specifications. Builders rely on their mechanical contractors to properly size the system(s) in homes they build or remodel. They are the ones who pull the mechanical permit and do the work, which is subject to inspection.

Until municipalities started to require manual J and S reports to be submitted for review prior to permitting, most HVAC sizing was performed using rules of thumb such as 1 ton/400 SF to 1 ton/600SF of living area. I suspect they still are where permits aren't required and there is no independent review. The use of rules of thumb typically results in larger equipment than would be determined by using the industry best practice-- which is to size equipment based on ACCA manual J load calculations and manual S. Consider, too, the performance criteria: The performance standard in Residential Construction Performance Guidelines for Professional Builders and Remodelers published by the National Association of Home Builders requires only that the system be capable of delivering a 78F indoor temperature when the outdoor temperature is at summer design temperatures (the requirement is superseded by any local code requirements.) Relative humidity isn't considered, although it contributes to occupant comfort. An over-sized system which delivers the required cooling--including one that short cycles--could meet that performance criterion despite uncomfortable indoor relative humidity.

It seems wasteful to pay for inverter heat pump and then only use it in cooling mode. I would think it would cost less to install an inverter type AC condenser but perhaps this may not be true in the Katy, Texas market.

Mike Home -- yeah you would think that, but they don't make a "true" inverter type AC condenser like the Bosch Bova 2.0 that doesn't require replacing the whole system.

All the others that compete with the Bosch BOVA 2.0 aren't heat pump only, but they are all communicating systems that require: new furnace, new evap coil, inverter condenser, proprietary thermostat. -- Some times things aren't as they seem. The thermostat alone could cost you $1000. Yeah that's not wasteful, that is proper! ( There's more than one way to argue it.) Well we want to be able to say we installed a $30,000 HVAC system that is all the same brand name. Ok, go for it. Then don't complain when communication hell breaks out and the thing is spitting out error codes at every whim because this won't seem wasteful? The road to hell is paved with good intentions.

It's more wasteful to again what I have said countless times now: to rip out and replace a perfectly still good furnace. Bosch doesn't make AC only condensers in the BOVA 2.0 model. If you want the AC you pay for the heat pump. I know what you're thinking --- I could set these up as duel fuel -- yeah I could, but that jacks up costs for a market that is going to use heating maybe 3 weeks on an off, it's simply not worth it for an area that uses AC for 10! Months out of the year. You do realize there is only 12 months in a year right? Then there's mild weather season on both sides of that. Winter here rarely starts much before Dec 21, you know the official start of winter. Sometimes we get blasts of cold that might last a week after Dec 21, but those temps are still usually in the 30's-40's with highs in the 50's. Some times a wee bit colder, but it doesn't last more than a few weeks and usually not even that long. 1 Year in over 26 years of living here was there a really cold winter where it hung around for more than a week and it's been so long ago I don't even remember what year it was. That winter we had lows in the 20's every night most days highs struggled to get to the 30's. --- that kind of cold here is RARE!

We get in the news for the Texas grid going down due to freezing rain and everyone assumes we were without heat for 6 months. LOL. again these are all myths. It wasn't what I would call "fun" but it was like 2 days.

The contractor quotes the same size. Customer asks is it possible the equipment is over sized and if it can be replaced with a 3 ton AC and 60K BTU furnace so to save money on the installation costs. I don't know where you picked up I suggested replacing a 12-15 old perfectly good furnace.

LOL. People don't talk like that here mike home after just going thru 10 months of hell on earth. You living in NJ have no idea what the summers are like here do you? Do you. ah ha, ha, ha, ha.

If you want to visit -- get to the heartland of America -- Take I35 south down to Dallas the soon to be NYC of Texas -- hop on I45 south, keep driving on I45 south until you reach the Gates of Hell -- I'm situated about 3 clicks west thereof.

They start considering replacing the AC because it was repaired and it's not keeping up (not cooling well) they are more likely to believe the AC is undersized not oversized. I tell them it's natural for you to believe your current AC seems like it is undersized because running low on refrigerant will give you that "feeling". I have never once been told in person here at someone's home --- hey I think I have too much cooling here. NEVER. (Keywords *in person* at someone's house paying for service) Not a single time in OVER 25 years.

To save money? at best the difference in cost again might be $700 -- the savings come by not replacing the good furnace, keeping the size the furnace can support. Well the furnace is 25 years old at this point... well furnaces can last longer than 25 years here. Certainly it may need repairs -- but if the goal is to save money, repairs is it.

Most of the posters of this forum asking for advice about replacing their furnaces, air conditioners, and heat pumps don't live in the climates like Katy, Texas. So the advice you provide as a 30 year HVAC professional has to be taken into account for those other climates.

When you don't adhere to the same thing? Like suggesting someone is going to think their unit is oversized in my climate after going thru a 10 month cooling season? I used to live in Chicago, I know what a 3 month AC season is like. I also know what trying to keep data rooms cool in -40 degree windchills is like. Worse than a hot attic if you can imagine it. -- That was another life time ago.

Advice, I say opinion. I'm not truly giving advice. I am pointing out the cons of the game. It is a game. If I were giving advice, I'd be doing it in person.

You give advice as a home owner with no ownership in the game. No experience and clearly no experience of a 10 month cooling season. If you had those things mike home it would clearly show in how you discuss various things here.

You disparage performing a heating and cooling calculation whenever it is mentioned. I am not sure why if most your business is doing repairs. However when people come to this forum asking for advice about spending $15K - $20K on new HVAC equipment you don't think doing a load calculation has any value due to the reasons you have stated in the past.

Well why wouldn't someone think logically about such things? You talk about saving money as an example.. the repair to a 25 year old furnace is $1200 according to the OP. The cost for replacing the system, that isn't the same size as the system it replaces is not being quoted at $15,000... the quotes are $11,747 up to $13,376.

There were other quotes that we don't know except the others were not quoted as the same size as what the OP has at here house. So why is that?

Could it be that they don't want to offer "Just a furnace" as a fix -- by saying the system size is wrong? We don't know, but it's an easy way for HVAC companies to run from a repair by just saying the current size is wrong so we must replace everything to make more money? They aren't making less money doing that are they?

The OP doesn't say anything about having trouble with the AC yet. Well it's 25 years so just replace it too. So what am I saying exactly? Am I saying not to. Am I giving advice not to? No. I am questing things as to why.

If the method was a legit method? One should be able to perceive all the quotes coming in to suggest the same size? People here say no, and see no problem with it? why?

The only reason the OP came to this conclusion is the furnace broke and because it's broken and old someone said you should replace the whole thing. There's the argument of refrigerant changes. Sure you could argue that but the A2L furnaces can work with older AC's.

How hard is it to deal with an AC with issues (25 years old) from a 3 month cooling season perspective? The manufacturers want complete systems because they make more money for selling a "complete system" - the same can be said by replacing an entire system versus just selling a furnace. (or repairing the furnace) -- they gave that option, so it's not like it's a cracked heat exchanger or something.

-------- so is this advice or just yet another opinion to consider? ---------

That is something the OP has to decide after this long and extensive homework session.

It's "mostly" a financial decision at the end of the day, wrapped with hopefully what will provide comfort for what ever the OP decides outside of the prying eyes of strangers who more like to argue than anything else.

For $1200 you could prove it again in your own mind if the system you have is the right size or not. It's sit there for 25 years, with no thought otherwise of it being the wrong size until now? We can only assume that: Yeah, because it's 25 years old. (If it was wrongly sized? How would it make it to year 25?

Let's not think about that. Let's think about "best practices" --- sure do what ever you want.

------------------

"The biggest myth is in all of this is the builder always installs the correctly sized equipment." Builders have never had an incentive to install larger, more expensive HVAC equipment than is necessary to meet code requirements or project specifications. Builders rely on their mechanical contractors to properly size the system(s) in homes they build or remodel. They are the ones who pull the mechanical permit and do the work, which is subject to inspection.

--------

Yeah builders are more likely to undercut to save a $1 here and there because the more houses they build those $$$ add up to more profit. If you build 10,000 homes and save a mere $2,500 in materials cost: $25 million.

Things like improper line set sizes, thin walled pvc drain pipes that crack when you attempt to cut them, drain pans a bit thicker than a sheet of aluminum foil. Let's not talk about grey flex either. LOL.

Sure builders make mistakes just like anyone else but usually it's toward the end of being smaller because it's cheaper to do so and builders are always building new and then going onto the next build.

That being said if a unit is not sized properly for AC in a 10 month use climate? The system is how likely to be still there 25 years later? Even 15 years later?

Inspections aren't going to have someone go back from a 3rd party to do all load calcs again. The inspections are primarily to check that building codes were followed. Codes have little to do with performance of the HVAC system or lack thereof.

This isn't to imply that building codes should not be followed.

--------

It's 6:08 am

"Codes have little to do with performance of the HVAC system or lack thereof." You tend to minimize things you don't understand, Ray. I think more educated sources in your industry would differ with you. Codes are updated on a three-year cycle. Codes have required progressively more efficient systems over time (e.g. higher SEERs and EERs,) better thermal envelopes (e.g., higher insulation R-values and air sealing,) ventilation and make-up air (improved indoor air quality,) and duct sealing (higher efficiency.) The current versions of the International Residential and International Mechanical Codes require performance testing of newly constructed homes including blower door tests (to test the sealing of the thermal envelope) and duct blaster tests (to measure duct leakage) respectively. Taken together, the changes are producing lower utility bills and improving homeowners' comfort. I would expect changing out a 25-year old (still operational) furnace should deliver on both.

Advice, I say opinion. I'm not truly giving advice. I am pointing out the cons of the game. It is a game. If I were giving advice, I'd be doing it in person.

You give advice as a home owner with no ownership in the game. No experience and clearly no experience of a 10 month cooling season. If you had those things mike home it would clearly show in how you discuss various things here.

Ray,

Posters come here to get input as to how to deal with an HVAC problem. Sometimes it is a simple problem, and other times it is complex and expensive. Call it advice or opinion they are looking for help. You say I have no ownership in the game, but neither do you or anyone else on this forum. The original poster doesn't live in a climate with a 10 month cooling season so I am not sure how that is relative to the decision he is trying to make.

You state you are pointing out the cons of the game. It is unfortunate but the HVAC industry has many con artists. This is why homeowners who have been conned in the past want to share their experiences.

Working alone and not following accepted industry standards and practices for 30 years does not result in 30 years of expert experience. To dispute the validity and importance of following accepted and recommended standards is proof enough that doing something the wrong way over and over again doesn't develop high levels of trade competence.

Working alone and not following accepted industry standards and practices for 30 years does not result in 30 years of expert experience.

I didn't just wake up one day 30 years ago and said I think I'll be a Texas licensed HVAC contractor. The trades don't work like that Mr. Fudd.

Accepted trade practices? Like repairing Air Conditioners. You do realize to fix something you have to be following some sort of accepted standards and practices? No, who am I kidding.

I started my own company in 2008, the only practices you've followed Mr. Fudd is delusions in your own mind.

Call it advice or opinion they are looking for help.

Mike home your definition of help and mine are two very different things. Saying well just do what industry standards say to do without and form of rationalized thinking?

The existing furnace / AC in this thread has heated and cooled that home for 25 years. And the only reason we are here? Is that people are HELPING?

Confusion run amok more like it. You can do what you want, if you believe "xyz" to be right -- opinion -- it's only money, if it doesn't work and eventually raises more questions about being sized right or not? Well rip it out again and start over.

Now that we've had this extensive talk about system sizing WHATEVER this home owner now does they'll be more aware to every run cycle / how the system performs / how long those cycles are, how comfortable or uncomfortable they are.

Psychological warfare of the mind. What is right, what is wrong... 25 years is a long time to heat and cool a home in a location that has 4 well defined seasons.

You state you are pointing out the cons of the game. It is unfortunate but the HVAC industry has many con artists. This is why homeowners who have been conned in the past want to share their experiences.

So my opinion is helping after all? You can't have it both ways mike home you can't say I'm not helping on the one end only to say I am helping on the back end.

You're words are neigther hot nor cold, but lukewarm and I spew them from my mouth.

You tend to minimize things you don't understand, Ray. I think more educated sources in your industry would differ with you. Codes are updated on a three-year cycle. Codes have required progressively more efficient systems over time (e.g. higher SEERs and EERs,)

Or I understand them fully and you don't understand because you're a builder Charles and pretending to know a little bit about HVAC, but not to the point you won't call your HVAC crews to do what you suggest you fully know and understand?

Kind of like the pot calling the kettle black.

Codes don't properly charge and air conditioner or heat pump. I've looked at the prettiest equipment installs known to man, passed codes, passed inspections and not working worth a flip. (how else would I be called instead of someone to check codes?)

Efficient systems: not really. Electrical resistance heating is 100% efficient, vs gas heating for my area is mostly 80% efficient. But electrical resistance heating costs more to operate and you'll keel over after a long winter running resistance heating than that inefficient gas furnace.

Certainly they have gotten gas upto 97% efficiency or so, but those options cost more up front as well as higher maintenance and repair costs.

Efficiency is a dual edged sword to hang your argument on Charles. Proves you are a builder after all. The HVAC contractor on speed dial has it's limitations, code book page 911.

How would I know that? I'm a HVAC repair man. --- You're long gone by then Charles.

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5:41 AM

"Efficient systems: not really. Electrical resistance heating is 100% efficient, vs gas heating for my area is mostly 80% efficient. But electrical resistance heating costs more to operate and you'll keep over after a long winter running resistance heating than that inefficient gas furnace. " You've confused thermal efficiency of a heating appliance with its operating cost, Ray. While both can be affected by the choice of fuel, thermal efficiency doesn't consider economics-- only the amount of energy converted per unit energy input.

"Codes don't properly charge and (sic) air conditioner or heat pump. I've looked at the prettiest equipment installs known to man, passed codes, passed inspections and not working worth a flip. (how else would I be called instead of someone to check codes?)" You've stated in other threads on houzz.com that you only service areas which don't require permits and inspections. If that's the case, then the improperly charged A/C or heat pumps you've worked on were installed without the benefit of inspections. That said, HVAC systems in new construction are typically subject to a state's statutory warranty requirement. If an HVAC system in a new home isn't performing to code standards, it's the home builder's obligation to repair it so that it does within the warranty period. In Virginia, that period is one year--which would include a full heating season and a full cooling season, during which system performance can be assessed.

You've confused thermal efficiency of a heating appliance with its operating cost, Ray

Charles, explaining it in layman's terms so an average home owner can understand that efficiency doesn't "always" mean cheaper utility bills. I'm not trying to talk to an engineer that only likes to hear himself speak in code language that most of the time leaves much to be desired.

You've stated in other threads on houzz.com that you only service areas which don't require permits and inspections.

Yes, Charles not all jurisidictions require permits. It just so happens I reside in one in which I have plenty of work from. There are plenty of other reasons why it happened like that, but it's not primarily because of the requirement or not to pull a permit... as I have said countless times before I am primarily an AC repairman.

Even in an area that requires permits, they don't require them if you are repairing an AC. Of which HVAC repairs make up over 90% of my work. If you have the ability to repair them, it's not a big leap to install one.

I know you're a builder and don't get the luxury of not being able to pull a permit and then hash it out to fix your code violations. Sorry I didn't make the laws.

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5:45 AM

"Charles, explaining it in layman's terms so an average home owner can understand that efficiency doesn't "always" mean cheaper utility bills." Your confusion shouldn't produce similar confusion for houzzers, Ray. You implied that increasing efficiency increases operating cost, but you've confounded variables. A higher AFUE (fuel efficiency) gas furnace will cost less to operate than a gas furnace with a lower AFUE rating. Period. Electric heat--or oil heat for that matter-- utilizes a different energy source which may cost more or less than gas depending on the locale. It's a confounding variable.

Determining which source of back-up heat is more appropriate for a particular homeowner's needs would consider the upfront, installed costs as well as the operating costs over the life expectancy of the two alternatives.

A higher AFUE (fuel efficiency) gas furnace will cost less to operate than a gas furnace with a lower AFUE rating. Period.

Only if you don't factor in maintenance and repair costs. How would you (a builder) know about maintenance or repair costs? (berate a repair man on how little he knows, yet he's made a 30+ year career out of it.)

I know what your role is in the housing market is Charles, obviously you're having trouble understanding it.

Plus a higher AFUE (fuel efficiency) gas furnace will cost more to install than a lesser fuel efficient furnace, but your maintenance and repair costs will be far less too with a lesser fuel efficienct furnace. $1200 for a 25 year old furnace / $??? for a 8 year old high efficiency furnace -- this is if you are lucky.

The argument isn't always just about efficiency, as repair / maintenance costs is always a concern as well or at least it should be other wise the home owner starts questioning even more when the last furnace operated without much fanfare or any hardly any cost whatsoever.

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5:49 AM

Well, you two have scared off the OP. Well done!

When people realize the work involved and then the ramifications of that work resulting in more or less a guess between choices presented this is often the outcome.

There was a time when things were much simpler, but those times are long gone.

I only focus on what I can control, not what I can't.

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6:10AM

" resulting in more or less a guess "

Be sure to inform your customers that you really don't know what you're doing and what the results will be of your work. You can only guess.

It's not unusual that posts/questions in HVAC remain unresolved and the OP flees. Berating, confusion, and criticism are common, both toward the OP and between the contributing professionals who take over the discussions (see above).

I think highlighting known attitudes and shortcomings of participants helps the OP validate or invalidate what some say.

You can only guess.

Ok then, what are the participants in this thread doing then if not guessing?

An HVAC system is 25 years old, the replacements are all different sizes from the original.

The HVAC system sat there for 25 years, heating / cooling that house all this time. Then the furnace breaks down is going to cost $1200 to fix it.

No Wait... it's the wrong size! oh no? Well we're not going to provide a quote to replace the furnace, because it's the wrong size after 25 years so we can get a full system replacement?

We don't know that either... but? Is this about money or the wrong size? I'm guessing, you're guessing. But based on 25 years, my guess is more of a statistical advantage. Playing the odds as they say in Vegas. What happens in Vegas stays in Vegas.

Well we are not guessing? Then what are you really doing?

I think highlighting known 'short comings' in the process helps the OP see how much or how little sizing is a part of process of getting it right versus getting sold for the sake of it.

Well -- you can only guess. You could also try thinking just a wee little bit, in addition to taking a guess.

---------

5:55 AM

No one here is advocating guessing, except the two contractors who didn't invest the time to check the equipment sizing following industry best practices (and code requirements depending on the locale.) The ACCA manual J is a prescribed load calculation process which was developed by your industry trade group and which has been in place for decades. That's more than adequate time to prove its usefulness. The manual J calculated loads are approximations--not exact solutions--but they're far removed from guesses. Exact solutions are pretty rare in the sciences, engineering, and tax accounting. We don't throw our hands up because we can't calculate an exact solution when an approximation is adequate for the purpose.

No one here is advocating guessing, except the two contractors who didn't invest the time to check the equipment sizing following industry best practices (and code requirements depending on the locale.)

So how was the original size determined 25 years ago? guess it was wrong.

The two who didn't do the calculation took a stab? those are wrong? ok sure I could agree with that.

The one who did do it -- is different than the original size that sat there for 25 years and the only reason we are having this debate is that the furnace broke down and is going to cost $1200 to repair.

You can argue go around in circles, flap your arms like a bird, do the hokey pokey turn yourself around... it still does little to explain how a broken furnace is leading a few to believe the sizing is all wrong.

I'm the only one suggesting that has a problem with this process? Yeah because I've seen this slight of hand trick before in person and the equipment it involved was much younger at only 5 1/2 years old.

Not saying this is what is going on here, but 25 years is a long time for the original equipment to sit there year after year (according to this story as presented here by OP) --- not saying anything in regard to them even having a smidgen of evidence the current system is not sized right.

How many cold winters that unit went thru? 3 month AC seasons? Not a single ounce of thought by the OP suggesting any sizing problems? none.

The heat load calculation is a tool, but not the only one.

-------

6:10 AM

We don't know how the size of the 25-year old furnace and air conditioner currently installed were determined nor does it matter. The OP's been presented with three different proposals from three different contractors. They asked for help to determine the proper size of replacement systems. That task is well scripted by the ACCA following the procedures in manuals J and S. I advocate a thorough inspection and testing of the duct system, too. Some or all of a 25-year old duct system likely needs to be replaced. Code requirements for duct systems have change a lot in the past 25 years. Sealing to meet current code requirements may decrease the required size of both the furnace and A/C reducing the replacement cost and operating costs as well.

I don't believe a HVAC company would last long telling clients they need to pay to test and inspect their 25 year old duct work, and certainly after telling them the 25 year old duct system needs replaced when all they wanted was a A/C unit replaced. If I wanted my roof replaced and the roofer told me I also needed to replace the trusses because the code changed I'd tell them to take a hike.
Wasting time to do a full blown load calculation including testing the duct work for a replacement job is rare, and almost never done by any HVAC contractor, this is reality.

Diagnosis before prescription is always a good approach. Doing so can make a replacement contractor stand out from the crowd. Performance testing of duct work is required by code in most municipalities for new construction. It's also required by a number of states including California for replacement systems. It's required in Texas for replacement systems if any of the duct work is in unconditioned spaces like garages or attics. It's required in Ohio if the air handler is replaced and it's installed in an unconditioned space. Of course, if your work is performed exclusively without permits and inspections, who'll know?

"CRH: Performance testing of duct work is required by code in most municipalities for new construction. It's also required by a number of states including California for replacement systems. It's required in Texas for replacement systems if any of the duct work is in unconditioned spaces like garages or attics."

When did the TX requirement go into effect? There was no apparent/obvious "performance testing of duct work" done when my system was replaced in January 2022, other than running the new system while it was charged with refrigerant*. All the duct work, including the two return paths, are in the attic.

*There was a valve leak that became apparent in April 2022 by way of a fault code F7 that I discovered when I just happened to open the service panel on the outdoor unit for a look-see at what service info is in there. ...Yeah, homeowner overstepping the bounds of amateur/idiot vs. professional/genius. I've continued to check it periodically.

@dadoes,

My understanding is that duct leakage testing has been required at least since the 2018 International Energy Conservation Code (IECC) was adopted by Texas in September 2019. The testing requirement applies only if ducts are installed in unconditioned spaces (i.e., outside the thermal envelope.) The 2021 IECC has not yet been adopted statewide in Texas; it requires duct leakage testing for ducts both inside and outside the thermal envelope. However, some Texas cities including Houston have their own energy codes. Houston adopted the 2021 IECC (in effect since January 1, 2024,) with some specific local amendments and additions.

" Wasting time to do a full blown load calculation including testing the duct work for a replacement job is rare "

Load calcs are increasingly required when pulling a building permit for a new install or replacement of existing equipment, along with HERS testing. What's a waste of time is reading your uninformed views.

It's remarkable how quickly our HVAC "pros" retreat from the conversation when it becomes apparent to everyone that they aren't aware of code requirements and aren't doing what is required by code.

I don't think it's just a code compliance thing. When an industry association recommends that particular steps should be done as accepted and required standards of proper professional trade practices, and when those recommendations are not controversial or disputed, it's telling that someone in the business still disputes the credibility and value of what to so many others is just another step that's always done. Done because it's a requirement of doing a proper job. Whether or not it's required for building permit and whether or not a building permit is even required.

"Wasting time to do a full blown load calculation including testing the duct work for a replacement job is rare, and almost never done by any HVAC contractor, this is reality."

Sadly, I think this statement is true. Unless it's a code requirement (and "best practices" be damned), I don't think any HVAC contractor:

a) wants/has the knowledge to do a meaningful Manual J/Manual D calculation,

B) wants/has the knowledge to do a meaningful duct leakage evaluation

C) wants to include this in their bid for fear of "sticker shock" by the homeowner

Remember, these guys aren't rocket scientists!

Elmer, I find it interesting that you complained about Ray’s long and rambling comment, yet your own response suffers from major flaws. Your sentences run far too long and pile on clauses until the main point becomes almost impossible to follow. Repetition does not strengthen an argument, and using the word “required” multiple times in the same breath does not make the idea clear or correct. I have copied your original comment below so you can look at it again with a fresh perspective encase you accidentally delete it, like the one where you said you have all your teeth when confused on a big word.

• 📷Elmer J Fudd1 hour ago last modified: 1 hour ago: I don't think it's just a code compliance thing. When an industry association recommends that particular steps should be done as accepted and required standards of proper professional trade practices, and when those recommendations are not controversial or disputed, it's telling that someone in the business still disputes the credibility and value of what to so many others is just another step that's always done. Done because it's a requirement of doing a proper job. Whether or not it's required for building permit and whether or not a building permit is even required.

This one didn't come across as a meltdown, but it does read as if you're frustrated or defensive, and worked up about something else. If something else is bothering you, you are welcome to explain. Were the other women on another thread mean to you again? If so just apologize and ask forgiveness. As for this discussion where professionals usually know best, comments should be clear and smooth, so maybe it's to far above your pay grade to understand.

"Remember, these guys aren't rocket scientists!"

Of course not, comparing HVAC to rockets, our job is to pull out a new rocket, set it on the launching pad, hook up the lines and plug her in. We're not in the business to re-engineer a rocket or a condensing unit, just install it.

The time to gather the data and create a loss/gain calculation, and when the average win for a HVAC bid is only 15% to 35% the time adds up. An accurate and correct calculation takes at least 45 minutes and up to 2 hours not including travel time. The expense to keep a tech on the clock is around 150/hr if all expenses were calculated in, even if the tech was generating no income for the company. That one bid will cost a company $300 to $400 and isn't reality in the field. The customer is going to get a rule of thumb bid.

People looking through a window with the illusion these calculations will be done correct and with precision are delusional when getting a bid. Even in the two dozen states requiring a Manual J calculation, for a bid it isn't going to happen. And even after the bid is accepted the J manual inputs are going to be a lot of defaults stuck into the program. Percentage of shaded glass, really? oh maybe 20% sounds good--click. I suggest those who haven't done one should limit their comments with a curious tone.

But....But California has a Hers rater checkout the work!! Yea, and if the system works right, and the square footage and window sizes look close compared to the submitted Manual J report it gets the green light. And he or she isn't going to replicate the original report to find out. If it doesn't work right, if or if not the manual J report was right on the mark the contractor must still make it right. So for a replacement, a full gain/loss calculation is hogwash.