AC Install with Heat Pump and remove oil fired boiler?

12 years ago

Hi there,

I'm doing a gut renovation of a circa 1840 colonial in the Hudson Valley, NY. House has a oil fired hot water system, but the radiators are in the way for the most part and have been removed. The plan was to put in radiant heat, but getting outrageous quotes to install...

I'm thinking of just adding a heat pump to the AC system I'm putting in and losing the boiler system altogether, and wanted to get some other opinions. If I do this, do I need 2 separate condensers if I were to do a zone for each floor? Or will the 3 ton until that the installer spec'd work?

Electricity averaged 0.0635/KWH last year if that is helpful info.

Many thanks, Mike

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Comments (5)

mike_home
12 years ago
Your electric rate seems too low for the New York State region. Are you sure it is correct? If it is, then a heat pump will be cheaper to operate than an oil fired boiler.

What is the total area of the first and second floors? The best solution is to have a separate condenser for each floor. However if you are putting in new duct work, you should be able to keep floors at the desired temperature with one system and zoning.

No one on this forum will be able to advise you if a 3 ton system is adequate. You need to insist on the contractor performing a Manual J load calculation and giving you a copy of it to you. You have an old house which I presume has little insulation in the exterior walls. The calculation needs to be done carefully with some assumptions about insulation and air infiltration.
stuntmanmike
Original Author
12 years ago
That was off the central hudson website, so have to assume it's correct...

The total area of the first and second floors is 1740 sq ft. This would be all new duct work, and I plan to spray foam the entire house as I have all walls open right now.

Thanks
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I agree with neo about getting a heat pump instead of straight AC unit. I live in midwest and have 1931 home with hot water boiler. AC had been installed in the '80s. Last year finally konked out, and we replaced with a heat pump. HOW DELIGHTFUL to have heat quickly when it's 67 daytime/45 nighttime. With only the boiler, it took a few hours before the house really would warm up to be comfortable on spring/fall days like this. We now have very inexpensive heat on days like this, and wow do we like it. We have ours on 1 Thermostat with the boiler. The heat pump cuts out at 40 degrees and switches over to the boiler at that point. That was where we ended up being the most comfortable. Others will run them at even lower outside temps. Getting back to your system. Have you considered 80% boilers instead of the 90% condensing boilers? They are much simpler systems, with fewer complex parts and as they are cast iron, are less expensive. If you can get one into the space, I would look at the cost/benefit to that as well. I agree with mnk about considering a straight hot water heater for bathing and cooking water. Just an option to also consider. Do the math and see what works out the best.
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I live in Harford County in an all-electric home. The cost of running a heat pump in the winter varies with the outside temperature. As outdoor temps drop, the btu's produced from the heat pump drops, and the C.O.P. (coefficient of performance) also drops. COP is the efficiency of the heat pump. At 32F outside, a typical heat pump has a COP of 3. Cost of 1 million btus at 13.5 cents per kw-hr, COP = 3: (1,000,000 btu / 3413 btu per kw-hr) x $.135 / 3 = $13.18. So the cost of 111 million btu = $13.18 x 111 = $1464. Don't be fooled by SEER. 44% of the value of the SEER calc is at 67 and 72F outdoor temps. I don't run my a/c at these outdoor temps. EER determines your true cooling costs. Whichever SEER system you get, you want 12 EER and 9 HSPF minimum. Also, because you are looking at a heat pump, you want full btus at the 47F rating temperature. Anotherwords, a 3-ton system should be 36,000 btu, not 33,000. Some condenser/coil combos are weak on heating btu's. The Trane XL16i is notorious for weak heating btu's. Good luck.
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ionized_gw
12 years ago
To get a true electric rate, you need to calculate in all the surcharges and adjustments on the bill which can be substantial. If you have a bill from that company, just divide $/kWh and use that figure. Maybe they have a sample bill on their web site that would allow the same thing.

Is nat gas available where you live? What kind of shape is the boiler and tank in?

The Hudson Valley covers a surprisingly large climate range or is Hudson Valley the name of a burg? No matter, Mike_home's statement about the need for calculations is correct.

(Maybe crazy) idea for the pros here, but could the oil boiler be kept used for backup heat with a coil for the forced air? It might be worth considering for three reasons, first, cost could be favorable to electric strips, second, heat could be powered by a small generator in case of outage, third, you could use the oil of domestic hot water if gas is not available.
stuntmanmike
Original Author
12 years ago
Good idea on the bill.

Gas is not available. Boiler and tank are new in 2007. The actual city is New Paltz, NY.

Adding a coil to the boiler is an interesting thought. Thing is the cast iron is all removed so I'd have to do something like like that to tie into the A/C ductwork that is not yet installed.
ionized_gw
12 years ago
I am not a heat guy, but I am relatively certain that you can use your boiler to make DHW and heat the forced air. There are details that I can't address. The trouble with using it for back-up heat only is that it might be too expensive to keep it hot for stand-by heat. If you are using it for DHW, that would not be an issue. It may be way over capacity for hot water only. I don't know if that is a problem.

That is a very new oil system. I suppose you could sell it if you don't need it. It is new enough so there should be some interest in it.

AC Install with Heat Pump and remove oil fired boiler?

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AC Install with Heat Pump and remove oil fired boiler?

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