Zoned system questions?

[ditndave]

I am building a new home and getting lots of conflicting information about what is the best way to handle the heating and air conditionining on my home. It is a two story home, appx. 1400 sq. feet on the main floor and appx 1650 on the upper floor, with an unfinished basement. Everyone wants to handle this house differently.

I have one contractor who wants to install the following:
Main floor: 90,000 btu 80% efficient furnace
2.5 ton 10 seer a/c

Upper floor: 110,000 btu 80% efficinent furnace
3.5 ton 10 seer air conditioner (in attic)

I have another contractor who insists that a zoned system is better. He wants to have four zones, with a 93% furnace (he didn't specify the size), and a 14-15 seer 4 ton a/c to heat and cool the entire house. On our first meeting he wanted to do a 2 furnace 2 a/c system (comparable to the first contractor) but has just recently started talking about this zoned system.

I know a little about hvac but this is my first experience with zoned systems. He insists that it will heat and cool efficiently and cost less to run, but I am concerned about making sure the house is comfortable.

Thoughs, ideas? Costs from these bids are comparable to install. I rank efficiency nearly as high as comfort.

Thanks for any advice! Any questions I should ask that I am missing? I want to get this right!

Dave

[beenthere]

Either method will work, I'd prefer the 2 unit install.

I also think your contractor is over sizing your heat.

But, thats just a bad guess on my part, I didn't see the prints on your house.

Have either contractor done a real load calc on the house.

You may want to get a third contractor involved.

[BaldLoonie]

To me, 2 story with 2 systems makes the most sense. His sizing really confuses me. I sure don't see a bigger furnace upstairs, much of the heat from downstairs keeps the upstairs warm without heat on in the winter.

4 zones with big equipment can be a problem too, especially cooling. If only 1 zone calls, there's 4 tons of cold air trying to go through 1 small duct. He would install a bypass but that dumps cold air right into the return which short cycles the outdoor unit leaving poor humidity control. If I were zoning, I'd just do 2 zones, 1 per floor. If ducts are sized right, this should work fine. 2 stage furnace with a zone panel that knows how to properly stage it would be best.

Where are you at? 10 SEER vs 14 SEER is another issue obviously. Need to be in a very hot climate with high juice rates for 14 SEER to pay off. Usually if that high SEER is justified, 90+ furnace isn't.

[browntigerus]

Woa 90,000 + 110,000 for 3,000 sq ft house....

Where are you mn, alaska?

Large ducts with zoned system could work pretty good...

Two systems will work well too.... But 10SEER/80% - sucks.


Brian.

[ditndave]

I'm in Utah. I actually requested the high efficiency, because the guilt crept in at my last house with a 10 seer. Yes, both contractors told me they did load calculations on the house. I didn't ask to see them because they mean nothing to me, a layman. Do I need to know that information?



Dave

[beenthere]

Click on the bulls eye above, and do your own.

Then you'll know if they did one, or are streching the truth to you.

It just sounds way too much for heat, or at least back wards.
You are having your house insulated aren't you.