They're almost certainly oversizing the systems, which is going to cause you more money down the road, less comfort, and more failures. You need a load calculation to determine sizing. Don't accept any rule of thumb, and get it in writing.

So this company was less expensive. Were the units quoted from the other company smaller?

To put this in perspective, I can cool about the size of your main floor (my house in Maryland) with 3.5/4 tons of cooling, and your contractor wants to use 7.5 tons. Not for new construction, NOT for a main floor.

Those are my thoughts. I would be more than happy to give you advice on getting the right system, but it has to start there. This is a major purchase, and a major investment, so make it worth it.

Thanks alot for the quick response, Ryan. The other bid calls for 2 York TG9S120D20MP11 95% furnaces and 1 York TG9S060B12MP11 furance. The AC units are 2 York TCGD60S41S1 13 SEER R-410a and 1 York TCGD36S41S1 13 SEER R-410a.

I guess I'm not really sure if this is smaller or not. I'll do some digging. I'll talk to our builder about a load calculation first thing tomorrow morning, too. Thanks!

If you get the load calc done to determine sizing, you're on the right road to a good, efficient, reliable HVAC system. Tell them you want a true "Manual J" (term used in the field) load calculation, and not rules of thumb for sizing.

Tempstar sizing:
1) 125k btu furnace, 5 ton a/c
2) 75k btu furnace, 2.5 ton a/c
3) 100k btu furnace, 4 ton a/c
Total: 300k btu's heating input, 11.5 tons a/c

York sizing:
1) 120k btu furnace, 5 ton a/c
1) 120k btu furnace, 5 ton a/c
1) 60k btu furnace, 3 ton a/c
Total: 300k btu's heating input, 13 tons a/c

I can assure you they're not doing this the way they should be. Another thing to keep in mind is ductwork. It too must be sized according to airflow calculation, or it too can causer efficiency and performance problems. Lots to consider in an HVAC system, but the results are worth it.

The sizing differences would alarm me, too. Sounds like one is guessing differently than the other.

Have you considered geothermal with (or without) radiant in-floor heating?

I would!

SR

We are also looking at radiant in-floor heating, especially in the basement...probably not geothermal, though.

You should probably consider geothermal. You might decide not to do it but it should at least be a consideration. As you get a larger house, the economies of scale make it more and more worth it. I don't know Iowa but my off the cuff feeling is that it is really cold and can get really hot. At 7000+ sq feet - I would suspect you are going to be spending some serious money heating and cooling it.

Look - my builder builds houses in that size range and he is really good. But he does tend to overdo things in the name of luxury. My 2050 sq ft 2nd floor is knee jerk sized (preliminarily) at 3.5 tons in North Carolina. I know we will probably do 2.5. How does 1500 in Iowa need 4 tons of cooling unless it gets hotter there than NC?

Re: david cary

Ditto

Re: hickoryhusker

Â"probably not geothermal"

Probably a BIG MISTAKE!!

HereÂs a quote from a previous post that applies to you - even more (6750sq ft vs. 3180sq ft)!

"Since youÂre custom building a new home why not consider leaving all the last century technologies behind and install a triple function geothermal heat pump with radiant in-floor heating? This way one unit will heat and air-condition with forced air, provide the most comfortable heating, radiant in-floor heating, and heat your domestic hot water. You will achieve the lowest operating and maintenance cost, greatest degree of comfort and safety and highest resale value. Not to mention itÂs THE most environmentally friendly way to space condition.

"3180 sq. ft."; whatÂs that going to cost to space-condition in 10 years with conventional technologies? Go cheap now and pay as long as you live there. Going with 21st century state of the art technology youÂll pay once and save year after year and get your money back when you cash out and sell.

Since were talking about first costs, as this is new construction, look at the cost differentials. Explore Âgreen mortgagesÂ, lower interest rates for going green. Research state, federal and utility incentives for installing geothermal. You can do better than Âsame old, same oldÂ; challenge yourselves!

IMO

SR"

IMPO

SR

hickory

two thoughts jump out.

1. you are dealing with incompetence

2.the systems mentioned are grossly oversized

I assume you have good new home construction/insulation qualities. I would fire the HVAC sub.

you need a load calculation. you need to thoroughly explore your heating and cooling options including fuel sources available.

you need to become informed on the Fed Govt Tax credits for HVAC and how to take advantage of them. see link below.

IMO

Here is a link that might be useful: Fed Govt HVAC Tax Credits

Those are natural gas furnaces? If so you really should go with a high efficiency condensing furnace - not the 92% models you have been quoted. One consideration is safety - sealed combustion systems have much lower risk of CO poisoning the occupants.

It will be well worth your time to talk with an energy rater or home energy auditor BEFORE your new home is complete. You may be able to spend a little more on insulation and sealing, and a lot less on the HVAC. Some things can be done at the building stage that can't be retrofitted - like insulation under the slab.

As others have mentioned, the "manual J" calculation is critical. An oversized AC will run on short cycles, causing your house to be cold and clammy.

Check out those tax credits - you won't regret geothermal.

Thanks so much for all your help. The HVAC sub is doing a load calculation right now. He is raising more red flags, though, because he says he doesn't normally do it unless asked...says it's not a true reflection of the size of system needed. I am sure a load calc has it's limitations/margins for error but, come on, it's going to give us a better idea of what we need.

I'll let you guys know what I find out. I'm meeting with him and our builder on Friday, too. I'm hoping to get the load calc back before then.

Also, you have convinced me to at least take a look at geothermal -- 30% tax credit, uncapped? Is that correct? Are there any income restrictions on this tax credit? I assume this is something new.

Tax credit is new - no income limits. I started to relook at geothermal because of it - but my lot is pretty small and climate is mild etc etc.

While we are on the subject - solar hot water is a pretty good deal because of tax credits. Around here it is about $6000 and tax credits are $3400 (combined federal and state). That makes the payback pretty quick. Solar panels (PV) have a combined tax credit of 65% here - with a $10,000 cap on state and no cap on federal. Again - makes it reasonable. In NC at least - income limits are not the problem - the only people who can take advantage are people with high incomes. The tax credit can't be more than the tax liability (NOTE - federal does not work this way). Anyway - the only people who can really take advantage are people with 6 figures and up.

Regarding income limits: check with a good tax CPA! We put in a 6KW solar system, expecting to get the tax credit. We had asked the installer if there were limits and they assured us there would be no problem with us getting them. Because of income limits and the AMT, it took 3 years before we were allowed to have the credits!

This is in California.

OK...here's an update. Our contractor has gotten some info and a quote on a geothermal system. It obviously raises many question, so hopefully you guys can help me out. Here are the details:

The bid is for $58-60k (depending on # of wells dug) and includes the wells, equipment, 8-9 ton system, a 5-zoned system (1 on the second floor, 2 in the basement and 2 on the main floor). This bid does not include in-floor heating in the basement, which would be an extra $10k if run off an electric boiler or $20k is run via the geothermal system. The big price increase is because he would have to dig two additional wells. With the geothermal, we would have to use electric to run the system approximately two weeks out of the year.

My HVAC bid is for $27k.

There are several discounts to take into account with the geothermal. There is a break on our electric rate after the first 700 kWatts -- about 3.5 cents vs. 7 cents (this is an estimate off the top of our contractor's head). Plus a $2k rebate from the power company (there are smaller rebates for the furnaces). And, of course, there is the 30% tax credit.

The HVAC guys also ran a Manual J load calc. Here are the findings:

Second floor heating load = 35614 Btuh and Cooling load = 27177 Btuh. (there is an open entry and great room, so they included heating that area which bumped the square footage up to 2622.

North zone (first floor and basement) heating load = 50531 Btuh and cooling load = 27266 Btuh. Square footage is 975 in the basement and 990 on the main floor.

South zone (first floor and basement) heating load = 79154 Btuh and cooling load = 43044 Btuh. Square footage is 1750 on the main floor and 1750 in the basement.

They said the bigger sizes for their systems was due mainly to the cooling aspects and "they wouldn't want to put in a system that is too small for your house". Also, another thing to consider is we are up on a hill and it is VERY windy.

Again, here is what they proposed:

Main floor -- 125,000 BTU 92% furnace; 5 ton 14 SEER A/C; Ductwork, humidifier, digital thermostat (I'm assuming this is the south zone)

Main floor -- 75,000 BTU 92% furnace; 2.5 ton 14 SEER A/C; Ductwork, humidifier, digital thermostat (must be the north zone)

2nd floor -- 100,000 BTU 92% furnace; 4 ton 14 SEER A/C; Ductwork, humidifier, digital thermostat

I have the entire report, so if you have more specific questions, please ask.

With just the 30% tax credit, there is still a $16k difference in price. Not sure when our break-even point would be (we're looking into it now and I'll post more later), but obviously that is alot of money. We can have an independent company run a cost comparison and calculate a breakeven point for $300. This seems well worth it us us.

Thoughts?

Still oversizing thee first main floor system (5 ton) and second floor (4 ton) system in my opinion. According to your loads--I'm not taking into account your required sensible heat ratio--I would say a 4 ton and a 2.5 ton would cover it, respectively. But, I'm not on the job site to make that call. I still find it odd they aren't using their own load calcs. On the second floor you have about 200% the heat loss, and I added a little safety factor to the loss, which should be minimal on the second floor. They likely did that because they had to with the 4 ton A/C.

Others can give their feedback on the geothermal option... but I wanted to get my .02 in on the load calc situation. Good for you for getting one done; now if only they'd use their results in a seemingly correct way... You can ask them why they're oversizing in 2 zones. Sure, you don't want a system too small; I understand that and probably would round up myself. But the capacities still don't make sense. You can examine this for yourself: 1 ton = 12,000 btu's.

Is the house already built? You'd be better off spending some $$$ on better insulation, air tightness and triple-glazed windows to get your heating/cooling loads down. We're in a colder climate than you and a our house has a heating load that's about 1/3rd of yours (with an outdoor design temperature of -10F) and a house that's about 2/3 the size of yours. You'll save in both initial equipment costs and operating costs that will pay back over and over. BTW, we have geothermal but only need 4 tons for everything (about 4600 square feet heated/cooled). The smaller the system, the lower the drilling costs for the ground loops.

Paul.

Yes, A/C's are grossly oversized!

Here is something you should look into for new construction or modifying what you have.

Also, Play the ENERGY WISE audio.

ENERGY WISE Guaranteed Energy Cost Savings

I am not associated with ENERGY WISE.
- udarrell

Here is a link that might be useful: ENERGY WISE

No, the house is not built yet. It is framed, though. My thought is to finalize all our plans for insulation and then revisit with the HVAC guys and geothermal. Thanks for all your help.