Yes, we are building a house of similar size with a walkout basement in an area with summers similar to Wilmington. I also got 2.5 tons of cooling. Our HVAC contractor did a Manual J by hand and got a slightly higher number.

However, you need to look at the sensible load and compare it with the sensible capacity of the unit under consideration. You might have to go to three tons.

creek side

Thanks for the response - it raises my confidence that the calculations are very much in the ball park. I'm thinking seriously about a heat pump with a gas furnace backup. What is your thinking for heat?

While our summer temps are much like your area, we don't get as cold, so I would have to guess.

From your HVAC-Calc numbers, you will definitely need another heat source besides a heat pump. You could probably manage with heat strips in the heat pump, but it probably would not make economic sense. The best fuel choice depends on what energy costs are in your area.

If natural gas is available, versus propane, it probably will be the choice, but you should run the numbers to make sure.

creek side - thanks for your comments.

Just finished calculating cost per million btu's.

Looking over my utility bill for the last 2 years, electricity has been about .17/kwh. Natural gas has run around $1.60 / ccf.

I think this gives me, for a heat pump with a cop of 2.5, 1000000/3414*.17/2.5=$19.92.

For a 95% AFUE natural gas furnace, it's 1000000/102000*1.60/.95 = $16.72.

If these calcs are right, looks more like I will go with gas furnace rather than a heat pump.

Looking at the product specs for my 3-ton 9 HSPF Goodman heat pump, a COP of 2.5 = 16 F outdoor temp. The heat pump wouldn't have enough heating capacity to solely supply and maintain the indoor setpoint.

If you think about running the heat pump in higher temps, like 35 F ambient, COP = 3.25, and 1 million btu's = $15.32. At 40F, COP = 5.45 = $14.43.

Dual fuel (heat pump + furnace) provides flexibility if one of the fuels jumps in price.

I've read that natural gas prices will be low this winter due to oversupply and a weak economy. Big swing from last year.

Take care.

garyg

Thanks for your comments - I'm learning a lot from them and others in the forum.

When I think about it, one of the potential HVAC equipment contractors talked about having his own heat pump kick in secondary heating at around 37 F. With your input this now takes on more meaning.

What I would hate to have to do is buy a high efficiency HP and an equally high efficiency gas furnace. I was targeting a high efficiency HP and an 80% two stage variable speed gas furnace.

This set up would give me good flexibility with fuel price swings. I will have to look into the cost of equipment further.

I've progressed to talking with HVAC contractors to get their recommendation on equipment. After talking with 8, I'm down to a leading candidate. Here's the proposed configuration, all Carrier equipment:
gas hot air furnace model 58MVC060,
heat pump model 25HNAG36,
Infinity controls,
Replace 6" round duct with 8" to improve air flow in one area of the house,
Put turning vanes in two locations in the duct work to further improve air flow;
All new lines, pad, pulls all permits, etc.

Warranty 10 years on parts and labor, lifetime on heat exchanger.

About $10.7K before tax credit, after rebates.

Any thoughts?

Be sure and get your AHRI certificate number to be sure you'll qualify for the Fed Tax Credit.

What inside E Coil were you quoted?

Should that 25HNA"G"36 be a 6 or 9 instead of a "G"?

chambery1 -

Yep - the G should be a 6.

In talking further with the contractor, he recommended showing me two more quotes - ala good and best to help me finalize my decision, as it is a lot of money.

He also added a written guarantee that if the equipment doesn't keep my house to spec conditions (ASHRAE) that they will replace the equipment installed with the next larger size at no cost to me.

Will meet with him tomorrow to go over final equipment choices and will post here.

Just a HO here, but also a CPA.

I could not find an AHRI certificate for the Fed Tax Credit combining the 25HNA636 with the 58MVC060. And keep in mind that the 58MVC060 at 95% efficiency will output a max of 57k BTUHs in the best of conditions while you say your heat loss calc was 60k. No real cushion in those numbers.

However, the 58MVC080 does qualify for the tax credit (see AHRI # 3379627) and should provide 76k BTUHs, giving you a 27% cushion at full stage. And as that unit is modulating, I would have to think it will provide the maximum efficiency right up to its limits which should be sufficient for your heating needs.

Again, I suggest you get the AHRI certificate before signing anything. It would be a waste to leave $1,500 on the table.

If the furnace is 95%, it qualifies for the federal tax credit (after checking, I see that it is 95% in the 60k size upflow configuration).

I see various matchups with the 25HNA636/58MVC060. I'd want to know what evaporator coil is also being quoted. I'd prefer to stay with the Carrier brand and the tin-plated copper model (10 year warranty, pretty standard today).

Thanks for the added comments - here are my follow-ups:

The manual J the first contractor calculated came to 48,000 BTU heat loss, so he sized it to the 60,000 BTU furnace. The evaporator is a Carrier CNTVP36ATA21 (or CNTVP42ATA21 depending if they can fit it in). This goes with the 25HNA636/58MVC060 combination.
A second contractor provided a slightly more expensive quote for a 58CVA110-f-1-20 furnace, CNPVP4821ATA 4 ton evaporator and 25HPA542H003 heat pump, with Infinity Control thermostat.

I'm leaning to the first contractor - less expensive and seemingly better equipment choice.

Other thoughts?

Well, just had a very interesting phone call from Contractor 2.
The factual part of it is he doubts Contractor 1 can do the job for the equipment cited. And that it would really cost $2,000 more than I have been quoted if he was to put in the same equipment.

Comments?

Decided to go with Contractor 1. They just finished the install today, ran systems thru their initial use and programmed the thermostat with same settings used with old system.

Initial impressions are: MUCH quieter system; very clean installation by the contractor.

Look forward to seeing how the heating / cooling bills compare.

Thanks for everyone's inputs.