HVAC estimate

16 years ago

We are building a 2600 SF two story (basically a box) in middle TN. We recently got a estimate for the HVAC system. The total would be close to $11,000. That includes labor and material. It sounds reasonable to me but wanted to get some other opinions. Is the Dual unit a good choice? Propane would be the backup.

Rheem 2.5 Ton 14 Seer Dual Fuel Heat Pump

Downstairs Unit Model # RQPWB030JK08E

Warranty: 10 Year Compressor, 10 Year Parts, 2 Year Labor

Total Cost $6,100.00

Rheem 2.5 Ton 13 Seer Package Heat Pump

Downstairs Unit Model # RQNMA030JK010

Warranty: 10 Year Compressor, 10 Year Parts, 2 Year Labor

Total Cost $4,635.00

Thanks...

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Comments (7)

david_cary
16 years ago
Best to post on HVAC forum.

The thing to always ask is this unit(s) oversized? It would be wise to go above code on insulation etc and then downsize your units. What I am amazed is that code has not caught up with just reasonable standards. I would think the code writers could do the math for reasonable payoff things to do and make them code. Say anything with a less than 10 year payoff....

Obviously low-e windows, up the attic insulation to r-40, foam all windows and doors, radiant barrier the attic, do your best to get ducts within conditioned space (although this can get expensive).

Go the HVAC forums and read up on the standard practice of oversizing units and why it is a bad idea (not just for $$$ sakes). The downside of learning is that you will want units with more features. Variable speed is really really nice. 2 stage is also really nice. It goes on from there...
creek_side
16 years ago
HVAC forum as suggested and also HVAC-Talk. Be sure to read the rules before posting there.

I seriously question five tons for a hopefully tight new construction 2,600 sf two story in Middle TN. In fact, it borders on the absurd. We currently live in a leaky 2,400 sf East TN two story and do just fine with a low end 3 1/2 ton unit.

Our new build is a 2,000+ sf up and down passive solar walkout totaling about 4,200 sf. We installed a single two stage 4 ton unit with a VS air handler. The only reason we have 4 tons instead of 3 tons, which is the calculated heat load, was the relatively low cost to go from 3 to 4 tons in the two stage unit and the fact that it should be able to heat the home without ever having to run expensive aux heat even on a very cold overcast day.

Here is a link that might be useful: HVAC-Talk
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creek_side
16 years ago
I missed the propane part. When you say propane would be the backup, do you mean the HVAC equipment would switch to propane in low temperatures, or you are planning a separate propane burning heater of some sort?
mgabriel
Original Author
16 years ago
It would switch to propane in low temperatures...

Thanks,
creek_side
16 years ago
Besides them seeming grossly over sized, I have to question the wisdom of dual fuel units in Middle Tennessee, especially the propane part.

With dual fuel units, you have an either or situation. Either you are heating with the heat pump or you are heating with gas. The switchover is normally set at the comfort balance point, which may not be the economic balance point, especially with a fuel as high priced as propane.

On the other hand, heat pumps with electric auxiliary heat continue to provide useful economically produced heat below the balance point, just not enough of it to totally heat the house without help. In that case, the heat strips come on in addition to the heat pump. In all but the low end systems, the heat strips are staged in order to keep their use to a minimum. Heat strips cost more to operate per BTU produced than a heat pump. Depending on the price of the propane, it may or may not be a more expensive heat source than the heat strips.

If it gets really, really cold out, a point can be reached where it makes no sense to run both the heat strips and the heat pump. In that case, more sophisticated thermostats or a dedicated outdoor thermostat can shut the heat pump off. In Tennessee's moderate winter temperatures, that rarely happens.

Did the contractor mention doing a Manual J load calc. You certainly need one to confirm that five ton requirement.
mgabriel
Original Author
16 years ago
He gave me estimates on several other units. I had requested the estimate on a dual unit only because of my experience with heat pumps. In the past, we have had gas and heat pumps and the heat pump never seemed to feel hot. Perhaps they are a lot better now. This is something we continue struggle back and forth. I would love to just go with a heat pump and eliminate the need for propane but I hate to have a house that does not feel warm in the winter time. We are also installing a fireplace insert that produces heat. Anyone live in the TN area and just heating your house with a heat pump. Thank you for all of your suggestions and advice.
creek_side
16 years ago
Anyone live in the TN area and just heating your house with a heat pump.

Yes, we have a heat pump only in our current house. Our new build is a passive solar home with a heat pump for summer cooling and winter heat at night and on cloudy days. We also installed a wood stove, mostly for ambiance. We also can heat with it in emergencies.

Both heat pumps have electric heat strips for an auxiliary heat source.