2 stage vs. 3 stage HVAC unit?

12 years ago

I am deciding between 2 HVAC units and looking for some advice on which unit to choose.

#1 - Bryant Evolution 95% efficient 3 stage variable speed gas furnace, 4 ton Evolution 2 stage 17.5 seer AC. Evolution control thermostat, high efficiency media filter, 10 year parts and labor, all installation services including removal of old system. Complete price is $11,950

#2. American Standard Freedom 95% 100k BTU 2 stage variable speed gas furnace, 4 ton Alligence 16 Seer 2 stage AC. Also included digital thermostat, Aprilaire 2410 media filter, complete install with all parts, 10 year warranty on parts and labor. Compleet price is $10,900

Both installers have been responsive and have good reputations. Is option #1 a better choice to save more money over the years, and does it provide better diagnostics with the evolution control thermostat? or save the cash and go with American Standard.

BTW, I am replacing a 18 year old 100k btu single stage unit that I thought performed fine until it died yesterday. Either unit will be an upgrade for the house, but hopefully this is 18 year investment.

Thanks for the help.

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Comments (6)

david_cary
12 years ago
You might want to give your location and realize that someone is going to suggest something else.

I personally can't see why you would need 3 stages. Option 1 will save a few dollars over the years but perhaps not enough to justify the price. It would depend where you live and how much electricity costs in the future. I doubt a 3rd stage actually saves any gas.
tigerdunes
12 years ago
GeoMason

It would be helpful to know your location.

Generally speaking, the more stages equal improved comfort and operational savings. It should be noted on furnaces that the manufacturers are moving toward full modulating mdls vs staged models for the high end. I do think the full modulating mdls are desirable for areas/climate with harsh winters. Carrier was supposed to introduce their full modulating mdl this summer and Trane/AmStd already have their full modulating model with the XC95m.

What size is your home?

The Evolution/Infinity systems with the Evolution thermostat are probably the best integrated system in the residential marketplace.

You can get an Evolution system with a 4 ton rated blower in an 80K size. not true with Trane/AmStd as you have to move up to a 100K mdl in the XV95 model. My point here is sizing can matter especially with operational costs. If you decide on the Trane, you want the correct thermostat specified.

I am a numbers person. If you post the evap coil mdl for each quoted system, I will try to give you the AHRI match with the performance/eff numbers for the AC.

IMO
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Sizing can be less of an issue when you have multiple units. Because each unit is controlled independently, provided of course the unit itself is not over sized for the area in which it serves resulting in excessive short cycling. In your case 3 ton plus 2 ton isn't necessarily equal to 5 tons of cooling... unless you drive those thermostats really low. By having two systems with total capacity of 5 tons (which, most of the time this would be oversized for a 1700 - 1800 sq ft structure) has a few advantages. 1. You have the ability to use one system only during low heat days or set the opposing unit higher. The unit set higher only runs if load conditions warrant.... meaning if it's not hot, the thermostat controlling the unit does not call... the unit can not run without a call... 2. Utility bills can be much less... because you rarely use both systems at the same time. You run the bedroom system when you sleep, the other when you're awake. If you have a home office in one the bedrooms you may need to rethink things a bit. 3. Extra capacity for when it's hot out. When it's hot you have the capacity to cool the home. (even while entertaining guests --- additional people add heat) Remember heat waves come, heat waves go... a so call 'properly sized' AC system is essentially properly sized roughly 10% of the time... especially if that system is a single speed AC system. Alot of people I come across like to sleep cool. So for that reason I doubt I would change the configuration of the space. Once you realize what you have, the choices you make are mostly budget type concerns. Essentially a set up like this runs like a 2 stage system. This kind of subject is above the pay grade of many... choose your contractor wisely. I service the Katy, Texas area.
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joe_mn
12 years ago
what died on system? heating is off this time of year. is it a control portion that died. fan blower? a/c compressor? coil leak?
GeorgeMason
Original Author
12 years ago
I live in SE PA outside of Philly. The house is approximately 3,400 sq feet. I get very little air circulation in the house with open windows and no trees for shade. So the house bakes in the summer. The system I am replacing is the original system, and is 100k BTU's. The compressor seized up. I was told by 2 different HVAC's guys if I replace the compressor I need to replace the AC unit, and need to match the existing furnace, so I am buying old inefficient technology. They both recommended to buy new and get the 10 year warranty. I will also get a $600 PECO rebate and (I think) $500 tax credit.

The Bryant dealer suggested he has some room in his quote, I am thinking he might come down a little. I plan on living in the house for a long time. I am thinking if can come down, I might go with him.

I am not sure what you are talking about with the evap coil mdl number. Should that be on the quote? Enclosed are the model numbers - Furnace M#355CAV060100, Air Conditioning M# 187BNA048

The installer is raving about how well integrated the Byrant system is, and with the control thermostat I can monitor the complete system. Is it worth it for a guy who sets the temp and never touches it? My wife and kids are in and out all day long.

I also forgot to mention the price may be a little higher than normal, they are doing some duct work and moving the outside pad a little further away.

I appreciate the help and advice.

GM
tigerdunes
12 years ago
GM

Current furnace is 100 KBTU at what efficiency?

Any problems heating home?

Any hot/cold spots in home?

Post back.

IMO
GeorgeMason
Original Author
12 years ago
Efficiency was 95%. I was happy with the old system. We noticed a small difference between upstairs and downstairs. One bedroom on the far end of the house does not quite cool or heat as well, but other bedrooms were fine.

thanks for your opinions.

2 stage vs. 3 stage HVAC unit?

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2 stage vs. 3 stage HVAC unit?

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