the 96V is a two stage var speed furnace. Has your GC/dealer provided load calculations both heating and cooling?

IMO

He has not, and I have now asked. Question on the setup. I asked about staging and I was told that as long as the furnace is two
stage, the a/c only needs to be single stage as the furnace blower will
regulate the airflow. Is that accurate? I just don't know and can't
find a definitive answer online.

Your post is a little confusing. Is the new furnace for the addition only or the original house plus the addition? Will the addition be a separate zone? What are the respective sizes of the original house and addition?

I think the contractor is telling you a 2-stage furnace will work is a single stage condenser. But it is going to be one fixed speed. There is nothing wrong with that except you the set up will not dehumidify as well as a 2-stage AC condenser.

We are doing an addition and the furnace & a/c I listed will be used for the entire house. The 2 zones are top floor and bottom 2 floors (entire house). Total house size - 3,800 sq. ft. ~1,250 below grade.

What my contractor told me is that we have a 2 stage furnace and the furnace will regulate the speed of the airflow for the heat in the winter and for the cold in the summer. IE, it didn't matter if the a/c unit was a single stage, the speed of the air would be regulated by the furnace. Contract calls for variable speed heat and a/c, so I want to make sure this is the case. We will be adding a dehumidifer (Honeywell?) to the setup as well.

Thanks for any and all feedback. Mike_home, does that help address the confusion?

If the basement is below grade, then it factors very little into the heating load, and nothing for the cooling load. Therefore for the purposes of HVAC your house is 3800 - 1250 or 2550. I assume the upstairs and downstairs floors are about the same at about 1250 sq. feet. This now makes more sense based on the sizes you posted.

In my mind a variable speed furnace has at least two stages. So that would be the 96V model. I am not a Rheem expert, and you have not specified what thermostat you are getting, but I think in cooling mode this set up operates at one speed. You would need a communicating thermostat and furnace set up in order for the furnace to increase or lower the blower speed. The reason to do that is to slow down the air flow so the AC can do a better job of dehumidification.

Are you talking to the general contractor about this? If so, he probably doesn't know the HVAC details and doesn't want to have to spend the extra money. If you suffer from humid summers then get the 2-stage AC condenser. It is worth it in my opinion.

Great, thanks Mike. I am indeed talking with the general contractor and I share the concern about him not wanting to spend the extra money, even though we discussed variable speed at the beginning. I am in minneapolis so the summers can get pretty muggy.

Re: thermostat, one of my questions is the compatability of the model with an ecobee, nest, or Lync. I would like for the thermostat and humidistat to be incorporated into one. Some of the features seem like overkill so I may just stick with a simple programmable thermostat until I figure things out, but definitely would like to move to a "smart" thermostat in the next year.

+1

Above post by mike_home - Very good advice!

Mike has solid info. We will be building by years and and talked to a few builders. I've also done a lot of research on local HVAC companies and with zero doubt, I know who will install the system. I told each builder that I am selecting who will be installing the system. Some balked and Imtold those that did, you are not going to be building our house. Take it or leave it. This is a custom house and it's our way or kick rocks and walk. We have selected a great builder who has no issues at all with this. My house, my money, my equipment.

"My house, my money, my equipment."

I agree with the above post. Take control of the HVAC aspect
of the build away from the GC. Educate yourself; find your own HVAC contractor
and co-ordinate the installation with the GC.

IMPO

SR

What the contractor has proposed is a two stage heating system and a single stage cooling system. I'm guessing this is because heating is a more significant issue than cooling up there in Minnesota and this would be a cost-effective solution. If humidity bothers you in your summers, go with a 2 stage condenser. It won't cost that much more.

Here was response from HVAC specialist: What does it mean going through furnace vs. dedicated a/c unit? Am concerned there was no load calculation done

Will be 2 stage model R96V furnace

o The a/c will
flow through the furnace blower and will also be two stage (it will
have high, low, and off settings for air flow speeds).

o IF YOU
WANT A 2 STAGE AC THERE WILL BE A EXTRA CHARGE AS WE WILL HAVE TO GO TO 17 SEER
COMMUNICATING A/C, IN ORDER FOR THIS SYSTEM TO COMMUNICATE YOU WILL HAVE TO USE
THE ECONET SYSTEM WITCH DOESN't WORK WITH ZONE SYSTEMS, RHEEM IS WORKING ON
GETTING THAT ABILITY BUT NOW IT WONT WORK WITH THAT ZONE SYSTEM.

· Confirm it will include a zone panel that will
not allow high fire unless both zones are asking for heat.------NO SYSTEM WILL
WORK THAT WAY WITH THE ZONE SYSTEM IT IS ALL DONE BY THE BOARD IN THE FURNACE.

Load calculations being done

This is where you find out the general contractor did not budget for what was specified in the contract. He usually can get away with this for HVAC but you have to ask all these questions!

They are trying to convince you that if the furnace can operate in two stages, then so will the single stage AC. It doesn't really work that way.

I took a quick look at the Rheem 96V furnace installation manual. I see the control board is compatible with a non-communicating 2-stage thermostat. I am not a Rheem expert, but I think the thermostat could still do the staging in both directions. There should no need to spend the extra money on an Econet thermostat in my opinion, especially if it can't support zoning.

I think he is going to configure the zones so they are controlled by the furnace control board. I am a little concerned this HVAC contractor is not experienced with zoning and/or he is trying to implement the cheapest solution.

Now he is saying that the sub typically uses Goodman and he picked Rheem because he thought I wanted a "brand name". I don't know anything about a/c (as you can tell from my post). He is now going to propose a Goodman system instead of the Rheem...

If he did do a single stage a/c through the furnace would that be a problem?

"The a/c will flow through the furnace blower and will also be two stage (it will
have high, low, and off settings for air flow speeds)."

He either doesn't know what he's talking about (which I doubt) or he's bullsh_tting you. A single stage AC condenser won't operate as a 2 stage AC. The proposed system will be working as a 2 stage heating and single stage cooling system unless you pay extra for the 2 stage condenser.

Some people on this forum are very negative on Goodman. It seems we see a lot of negative posts. But it in all fairness the problems may be due more about bad installation than poor equipment. In my opinion you would be better off with a properly designed and installed Goodman system then a improper Rheem set up. Where I live in NJ you rarely see any Goodman equipment. I have no experience and no opinion other than what I have read.

The GC is relying on the fact that most of his customers know brands and nothing else. You are at the point of being more knowledgeable than him!

If you were not installing zoning then a single stage AC would not be a problem. My concern would be what will happen one one zone is closed and all the air has to go through a single zone? The furnace may be able to slow down the air flow, but there is a limit of how slow you can go before the coil becomes a frozen block of ice.

Maybe you should ask the GC the question. Tell him a 3 ton AC needs nominally 1200 CFM (cubic feet per minute) of air flow. Ask him to explain how this will work when a single zone is calling for cooling. He is likely to say "the furnace will handle it". Then great have him explain what will be the air flow with one or two zones operating.

If you were not installing zoning then a single stage AC would not be a problem. My concern would be what will happen one one zone is closed and all the air has to go through a single zone? The furnace may be able to slow down the air flow, but there is a limit of how slow you can go before the coil becomes a frozen block of ice.

If a zone system is installed properly with properly controls it is unlikely you would ever have the problem of a frozen coil any more than you would a system without zoning installed.

Many times builders use inferior controls, which lead to these kinds of problems.

Communicating systems can be controlled via zoning including using the communication stats, but this requires vast control knowledge that is typically not seen in a GC type arrangement, via a builder.

With that said: you could also revert to legacy controls with 2 stage condensers in a zoning application. Again this requires control knowledge.

Mike_Home and Austin Air - again, thank you for the great feedback. I sent those questions to the HVAC specialist and spoke over the phone. He is not worried about the coil freezing (also consider that he is a fan of bypass ducts). He is asking for $1,500 more to move from the R16a Rheem to the R17 2 stage although we had always discussed variable speeds. His perspective is that this is accomplished through the furnace and, while less efficient, will perform the job equally well.

He is also going to propose a Goodman system that will include a 2 stage furnace and 2 stage a/c (with no upcharge) that will rely on a Honeywell IAQ. Of course, I am skeptical the systems are comparable but will post when I receive the equipment specs.

When you go to 2 stage AC environment brands really don't matter all that much except in terms of functionality and warranty coverage.

Some manufacturer's do not have communication available at the lower end of the 2 speed configuration. As far as variable speed goes, he is referring to the variable speed blower which isn't the same thing as variable speed compressor.

With that said, Minnesota is such a short AC season, I think the variable speed compressor would be over kill for this climate.

I don't think the Rheem warranty is as good as the Goodman 2 speed system comes with additional conditional warranty coverage: 10 year replacement of outside condenser if compressor fails / life time heat exchanger warranty on furnace.

You just need to make sure the unit is registered with Goodman.

Additionally for an even better warranty you could go with Amana. This would give you life time replacement coverage for both the AC condenser and furnace heat exchanger. (The replacement coverage kicks in only in the even the compressor or heat changer fails.)

The rest of the equipment has a 10 year part warranty. I've installed quite a few 2 speed Goodman systems over the last several years in the way of communicating systems. It really is a great machine... the problem most have is with the name of the unit for some reason.

The Amana and Goodman are virtually identical machines... except for the model numbers and serial numbers and the name on the side of the unit. It's more important who puts the machine in.

Ok, here is the proposed alternate system. Any thoughts on this Goodman model proposal?

Basically looking at Rheem: 2 stage furnace and single stage A/C:

Furnace: R96VA0852521MSB

Coil: RCF3621HTA

Condenser: RA1642AJ1NA

or Goodman 2 stage furnace and 2 stage A/C:

Furnace- GMVC961005CN

A/C-DSXC160481

Consumer reports doesn't give good reviews on either brands, although I read here on the forums it is about the install. According to Consumer Reports at 5 years, Goodman has lowest customer satisfaction and Rheem second lowest.

He initially proposed a Rheem 3 ton condenser, now it's a Rheem 3.5 ton or a Goodman 4 ton. Is he going to do a load calculation or just guess about the size?

Not sure about a 3 ton coil with a 3.5 ton condenser. Maybe it is a legal AHRI match, but perhaps a larger coil would give better performance numbers for a slight additional cost.

What is the coil for the Goodman system?

Stay with Rheem and insist on a written load calculation. Correct sizing goes along with equipment selection and install.

IMO

Does this look right? We have 2 zones and I note only one is in report. Zone 1 - upper level; Zone 2 - main floor and basement. Should the report plug in the proposed systems and confirm appropriateness? Not fully sure what I should be looking at here and confirming other than "Total heating required" and "Total cooling required".

He used 70 degrees as the indoor winter design temperature. The normal practice is to use 72 degrees. It usually does not make a big difference, but in your case the outdoor winter temperature is -12F so it could be significant.

It is showing you have 2X6 walls with R21 insulation. Is this correct? You also have attic insulation of R56. That would be impressive it were true. It is also showing the basement has a heat loss of about 22K BTU which almost twice first and second floors values. That doesn't make sense to me if the the basement is mostly underground.

I get the feeling this calculation was done because it is required by code or a rebate. The contractor may have fudge the calculation to make the answer come out to what he wanted.

Consumer reports doesn't give good reviews on either brands, although I read here on the forums it is about the install. According to Consumer Reports at 5 years, Goodman has lowest customer satisfaction and Rheem second lowest.

Source: Results are based on Consumer Reports’ 2016 Fall Product Reliability Survey of 14,452 owners of conventional central air conditioning systems. Differences of fewer than 6 points between brands aren’t meaningful. Our statistical model estimates breakage rates (a system breaks down or ceases to function well enough to sufficiently cool a home) by the 5th year of ownership, for systems that receive annual professional maintenance but are not covered by a service contract.

Problem is consumer reports do not test anything, they don't separate between model numbers of higher end equipment versus low end equipment. They group equipment by brand name alone.

Most people that choose the Goodman brand choose the lower end models. There is no discernible way to verify properly installation, proper maintenance among a host of other possible short comings that cause the equipment to fail prematurely.

When it comes to Consumer Reports and central HVAC systems, they merely send out a survey. People are more likely to publish 'dirty laundry' than clean laundry... because they have an axe to grind.

So Austin - would you go with the Rheem or Goodman proposal?

Rheem: 2 stage furnace and single stage A/C:

Furnace: R96VA0852521MSB

Coil: RCF3621HTA

Condenser: RA1642AJ1NA

or Goodman 2 stage furnace and 2 stage A/C:

Furnace- GMVC961005CN

A/C-DSXC160481

Still waiting on coil details.

Consumer Reports is a great organization but it is harder all the time for them to stay useful. With many items they like to rate for consumers, from bicycles to water heaters, the models change so frequently these days that it is really impossible to keep up. In those cases the articles that describe how to choose a good model that fits individual needs is often more useful than the ratings.

The Goodman 2 speed is a great machine, when installed right. Make sure they pair it with the communicating thermostat. (I've installed quite a few of them with no trouble, the hardest hurdle is the name on the side of the unit.) Because people like to trash talk various AC brands against others.

You could ask them what the difference is in cost for the Amana 2 speed as the warranty is lifetime replacement if the compressor fails, where as the warranty on the Goodman is 10 year replacement if the compressor fails... provided that you register it.

Compressors don't fail that often, but they do fail with all brands. So the argument other brands make is that Goodman / Amana brands compressor have more failures... which is not true.

Copeland compressors are not made by Goodman or Amana, Copeland is used in up to 90% of all AC units manufactured for USA market. The compressor isn't prone to more failure just because it's in a Goodman or Amana condensing unit.

But salesmanship has lead to the bash o'rama game in which every brand 'except' the one I am selling you is junk, garbage or whatever adjective will warm you over to buy 'my piece of junk' I am trying to sell you and in some cases they will be cheaper.

When problems develop with there brand, they will have somehow magically changed to a different brand and now they preach the new brand gospel.

I can't say a Rheem is any worse. The problem I have with Rheem is the design the evap coils they make the drain connection is off the corner of the coil so on a right handed install the coil drain port is butt up against the furnace. (horizontal installation)

I install equipment to continue to service it. The less access you have to the equipment the more problems you will have. Certainly I could use a 3 party brand Evap coil and match it with the Rheem, but why put in the Rheem if I am going to do this???

Certainly if you look hard enough there are design problems to one degree or another with every brand. But I live in a very humid climate and I do not need a bunch of condensate drain problems on every installation I do. ( I worked for another company in a different life that had these problems, repeatedly.)