bundle of questions for replacing HVAC?

finnickyaboutgreenOctober 31, 2011

We live in North Carolina. Just got an energy audit done and were recommended to replace our both HVAC's. We are thinking of replacing one unit only as of now- the on 1st floor. It is outside and is an airconditioner with gas furnace. Current Size is 3 tons, 10 seer and 80% AFUE. The house has good insulation and ducting and no hot-cold spots. Our annual energy bills are summer - $563 and winter- $ 658 and baseload is $835. We have flat cost of natural gas and electricity as: July-Oct $0.998/therm and 10.15 cents/kwh, November -June : $0.936/therm 9.15 cents /KWH.

My initial questions are:

1. Is a dual heat pump a good idea in our climate in NC?

2. Is 15.5 seer enough- that has been recommended.

3. What % efficiency for gas furnace- 95% ?

4. Is Carrier infinity brand good enough? I know pricing is importnat too but was just wondering if i can resolve these initial questions it will make us easier to go ahead. We have almost no idea about all this as this is our first home bought just last year.

5. Do we need a 2 stage or a 3 stage heat pump? A 3-stage has been recommnded ?

6. What are the most crucial factors that we need to be sure of when making the final decision?

thanks for any insights!

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These are good questions. Here are some answers:

1. The mild NC winters and low electricity rates are ideal for a heat pump.
2. A SEER of 15-16 is fine for your climate and electricity rates.
3. In cold climates a 95% efficienty furnace is recommended. I don't know if you need such a high efficiency especially if you are getting a dual fuel system. It may be overkill.
4. Infinity is the top of the Carrier line. It tends to be pricey, but it in some situations it is worth the extra money in my opinion.
5. Heat pumps come in one or two stages. The Infinity furnace comes in three stages. A two stage AC/heat pump is great if you have high humidity in the summer.
6. The most crucial factor is properly sized equipment installed by a competent contractor. You can buy the best equipment but it may never operate correctly if it was not installed properly or the wrong size.

Why did you get a recommentation to replace your systems? How old are they and are there any problems?

    Bookmark   October 31, 2011 at 7:40PM
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A highest efficiency single stage heatpump around 15 seer will save you significant money on energy in the summer. It will also be very competitive to natural gas in the winter. It may even be cheaper than your 80% gas furance in most instances.

Having a 95% furance might be overkill in your climate especially with a heatpump but it the cost isn't much more than the 80% I would consider.

    Bookmark   November 1, 2011 at 12:54PM
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What size living area?

What general location in NC?

If nat gas, then var speed 95% two stg furnace with high eff AC.

Second option, high eff heat pump with 80% two stg VS furnace.


    Bookmark   November 1, 2011 at 2:36PM
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IMHO, a variable speed blower (furnace) is more important than a 2-stage compressor (HP or AC) for humidity control.

As a rule of thumb, going from 10 SEER to 15 SEER might save you nearly 20% on your electric. That would be around $100/yr for your summer usage.

With gas it will depend on installation costs of the 95% over the current 80% you have. Otherwise you could figure a 15% reduction in the gas bill upgrading to the 95% furnace. The increased costs might eat up a lot of the savings.

Things get a little murkier when you go hybrid.

    Bookmark   November 1, 2011 at 5:11PM
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I generally agree with above post.

Nat gas rates have remained constant and in some markets have actually declined. Did you know that Piedmont Nat Gas? While electric rates have continued to march upward.

In fact, based on OP's rates, there is really no leverage in a dual fuel system.

Want to comment on installation of high eff condensing furnaces. If furnace is located in a very accessible place and has access to a close exterior wall for venting waste gas and fresh air for combustion, then this cost should be relatively inconsequential and not really a big deal at all.


    Bookmark   November 1, 2011 at 5:22PM
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