Advice needed for replacement HVAC

17 years ago

This is a great forum and I would appreciate your unbiased advice. I'm replacing a system in a late 60's, 3,400 sqft split level home (4 staggered half-levels connected with 3 short flights of enclosed stairs, very common in central VA). Current system: 1988 Carrier 150,000+ btu natural gas furnace w/ a mid-1990s Carrier 5 ton AC (indoor coil, outdoor condensor). The coolant leaked out and I've been advised to replace everything rather than leak-test & replace the coolant. The furnace short-cycles and the house doesn't reach even temps, but our gas & elec. bills are pretty reasonable for the area.

I'm getting estimates from 5 companies ranging from an owner/operator to large local operation with dozens of techs. My questions so far are:

1) Does it make sense to replace everything now? Everyone so far has said yes, based on the age and the likelihood of more leaks, but then again, I'm asking salespeople if they want to make a sale.

2) Only one company so far has said they will do a load-test before we select the exact units. Is that as important as they say, or is it hype?

3) One company looked around (no load test) and said they recommend a 4-ton unit w/ standard efficiency equip. They said the low-speed settings on high-efficiency units won't push enough air to cover our multi-levels, so we'd need to be on high speed all the time and that defeats the purpose of a high-efficiency unit. Does that make sense?

4) Several have recommended a dual-fuel furnace, w/ HP down to 40 and gas when it's colder. My experience is that HP air always feels cold. Also, it seems that a HP/AC would be running almost year-round and would not last as long as a dedicated AC.

5) Finally, two so far are Carrier reps and the other is Lennox. My thinking is that as long as I'm not buying contractor-grade, these brands, York and Trane should all last 15 years give or take. Any major red-flags on specific units?

Sorry for the long post, but THANK YOU for any insights you can share. BTW, my last estimates are in 3 days, so please reply soon...it's getting hot in here w/ no AC and I want to make a decision Monday afternoon!

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Comments (4)

ryanhughes
17 years ago
It makes sense to replace everything now and take advantage of all rebates available as well as the $1500 tax credit for high-efficiency purchase.

The first thing you want done is to have a heat load calc done to determine correct unit sizing. Then, have your ductwork thoroughly looked at, because most ductwork systems are undersized for the amount of air they are trying to move. You mention short cycling, so sizing may be an issue.

On low stage your home doesn't require full airflow/cooling capacity, so that comment doesn't really make sense to me. Two-stage equipment is sold all the time with satisfactory results. However I personally believe in more simplistic/standard equipment (13-15 SEER, single stage, variable speed indoor with 90+ AFUE for the furnace - setups that can qualify for the tax credit).

You pretty much nailed it with the brands question. I prefer Lennox, Carrier, and Trane, but just about any brand will do the job if installed properly.

What information on bids have you been given regarding ductwork condition, sizing, equipment model numbers?
va6strings
Original Author
17 years ago
THANKS to ryanhughes for the quick response! Sounds like you are a proponent of the load calc - makes me feel better.

The issue we have w/ duct sizing is that so little of it is accessible. Just finished a major remodel and I'm not up for tearing up walls, floors, etc. Too bad the unit d/n blow 6 months ago.

I think the guy who made the comment about the high-eff. units not being good for our cut-up house was a veteran who assessed that we have a LOT of ductwork, and it will take a high fan speed to move enough air through all the ducts for us to feel it. He didn't do any calcs to back that up. That's prob. why the prev. owners installed the 5 ton "beast" as one rep called it. Pls. let me know if that still sounds like too much gut and not enough science.

I don't have a lot of specific model #s, but I will get on that. One estimate proposed the Lennox G71 furnace that would qualify for the $1,500 rebate regardless what we do for AC, combined w/ a 14SEER Lennox AC. He said he would do a load test to right-size before we signed the contract. I'll provide more $$ once the last guys have bid.

Thanks so much for your input!
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va6strings
Original Author
17 years ago
Does anyone have any thoughts about not using a high-efficiency unit because it won't push enough air to cover a split-level house? The cost of a high-efficiency unit will eat up more than the tax credit, but, with a house that is 4 half-levels connected by stairs, does it makes sense that I might get more even temperatures from a unit that always pushes a lot of air?

Thanks!
ryanhughes
17 years ago
To tell you the truth I have not heard of anybody having issues because a 2-stage unit "does not push a lot of air." But, it would seem to make sense. However the other side of the argument is that not as much cooling capacity is needed, and hence less airflow is needed. 2-stage, if placed on the right ductwork system, can help with lowering humidity and more even temperatures. I myself have never been a huge proponent of them as I think similar comfort results can be obtained with just a good, properly-sized single stage unit. I would think if this issue is really the case, it would be talked about much more often, and it is not.