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Has anybody here seen a Northern New England home with an air-source heat pump (ASHP) and fossil fuel (oil or propane) as backup heat? I have forced air heat and air conditioning, and need to replace the AC system in the next few years. I already have all the ducts, so am not interested in ductless.
I like the concept of a "Cold Climate Air-Source Heat Pump" but am doubtful about the actual operating costs in New Hampshire, and whether they are tunable not just to be "green" but to actually save the homeowner money.
Can these be programmed to switch to fossil fuels based on cost (IOW, decreased efficiency of the heat pump) rather than just as emergency heat when the ASHP can no longer keep up with demand? I don't want to run the heat pump if burning oil provides cheaper heat ($/BTU) in January and February.
If power goes out and I'm running on a generator that won't power the compressor, does it recognize the compressor is out of service and go directly to fossil fuel heat?
What is the actual energy usage of a "cold climate" heat pump in a New Hampshire winter when the daily temperature range is 4°F-37°F?
Hoping somebody here has an ASHP+burner system in a cold climate and can talk about their real-life experience and actual winter heating electricity/fuel use.
If you want / need a system that includes a combustion furnace you are really looking at dual fuel / hybrid heat pumps. There may be "incentive programs" to help reduce the cost of these, but the substantial upfront costs of tearing out your existing furnace and central air to replace them with technologically advanced systems that might rely on fancy data feeds regarding real time energy prices is something that few folks will do...
I don't need anything close to real-time, just need to know there's a homeowner-adjustable setting to force "AUX" heat when COP is poor or when the compressor doesn't have any power (to avoid overtaxing the generator).
The existing furnace and central air system is approaching the end of it's useful lifespan, so replacement is unavoidable.
The thermostats have a AUX heat setting on them, when you turn it to AUX heat it should just use your secondary heating. There should also be setting on the heat pump for this so it's automatic. Alternatively a thermostat with outdoor temperature sensor should be able to switch it to AUX too.
Loss of power is good question, typically a generator is wired to the panel and with transfer panel with only a limited amount of circuits; refrigerators, stove, water pump etc. You wouldn't include the power for the heat pump in those circuits being powered by the generator.
Loss of power is good question, typically a generator is wired to the panel and with transfer panel with only a limited amount of circuits; refrigerators, stove, water pump etc. You wouldn't include the power for the heat pump in those circuits being powered by the generator.
Install a relay as a dead man's switch on the utility power source with N/O contacts serving the HP and N/C contacts serving the gas fired furnace. Power goes out, relay de-energizes, and furnace is the heat source when the stat demands, regardless of cost per btu.
I've only heard of one guy who had a heat pump in Maine and it worked well. He also had a new, very small house and it was air tight. He also had some sort of backup heat like electric baseboards for extra cold weather. Everyone else has terrible stories.
The biggest problem is the heat only comes out of the unit at 70 degrees. So by the time the air reaches you, it simply feels like cold air.
By comparison a forced hot air furnace comes out of the unit around 130 degrees. Huge difference.
I have 1 mini split heating my house. I have a wood stove for when I want, but would say it's a "must" in double digit negatives unless you do not mind it being in the high 60s in the house (my wife does mind).
These things are generally proven to provide 3x the amount of heat as the electricity they use as an Average COP in cold climates IF you get the top of the line product and it is sized correctly. I'm guessing that means Carrier for a ducted system. I am most familiar with Fujitsu/Mitsubishi ductless.
When you look at these you want to look at HSPF. 13 HSPF is excellent. 10 is just OK (My brand new Fujitsu is 13).
The Carriers should be able to be installed with a gas furnace with a Heat pump "lock out" that automatically turn the heat pump off at a particular temperature. This may no longer be necessary with the latest and greatest heat pump technology.
At $3.00 per gallon of propane and 0.18 cents per KWH, the heat pumps $17 per MM btu and your 95% furnace or boiler is $35 per MM btu, so you can easily do the math.
If you are having an automatic generator wired in, why not just give yourself a generator that can handle the heat pump and whatever else you want?
You do not want to have an automatic standby generator that is attached to more circuits than it can power anyway.
Do you currently use propane - how much do you pay for propane? How much do you pay per KWH on your electric bill?
Last edited by joe moving; 12-07-2016 at 04:45 PM..
These things are generally proven to provide 3x the amount of heat as the electricity they use as an Average COP in cold climates IF you get the top of the line product and it is sized correctly. I'm guessing that means Carrier for a ducted system. I am most familiar with Fujitsu/Mitsubishi ductless.
When you look at these you want to look at HSPF. 13 HSPF is excellent. 10 is just OK (My brand new Fujitsu is 13).
The Carriers should be able to be installed with a gas furnace with a Heat pump "lock out" that automatically turn the heat pump off at a particular temperature. This may no longer be necessary with the latest and greatest heat pump technology.
At $3.00 per gallon of propane and 0.18 cents per KWH, the heat pumps $17 per MM btu and your 95% furnace or boiler is $35 per MM btu, so you can easily do the math.
I see all these claims about Cold Climate Air-Source Heat Pump (ccASHP) and an average COP of 3, but no real information on what the true COP will be on a +/-10°F Northern New England January night.
The thermostats have a AUX heat setting on them, when you turn it to AUX heat it should just use your secondary heating. There should also be setting on the heat pump for this so it's automatic. Alternatively a thermostat with outdoor temperature sensor should be able to switch it to AUX too.
Loss of power is good question, typically a generator is wired to the panel and with transfer panel with only a limited amount of circuits; refrigerators, stove, water pump etc. You wouldn't include the power for the heat pump in those circuits being powered by the generator.
I live alittle north of Seattle and have a heat pump / AC and a gas fired furnace
The heat pump heats my home as long as the outside air temp is greater than 40 degrees ... if colder than 40 degrees the heat pump automatically switches to 'Aux' heat which is the gas fired furnace.
Very very efficient system that saves $$$ and provides you cheap AC in the summer and cheap heat all winter long.
Obviously in the NE your winters are more severe and your AUX heat will be used 95% of the time between Dec - Jan I would think
I see all these claims about Cold Climate Air-Source Heat Pump (ccASHP) and an average COP of 3, but no real information on what the true COP will be on a +/-10°F Northern New England January night.
As an example, the COP of a Mitsubishi FH15NA is 3.22 @ +17F if using the rated capacity . That is, if it's undersized, it will use more power, COP more like 2.2 at max power.
At +5F at maximum power, the COP is 1.75
I don't know what you pay for propane or oil but even at COP 1.75 it's cheaper for me than propane.
What do local installers say? I'd talk to a Carrier installer and ask if you still need gas backup. The newest units should run well into the negatives without a problem and fairly efficiently. Again these new units should all have Heat pump lockout capability, so if that is what you want to do when it gets to any particular temperature you can automatically turn on the gas at that point. Not sure what the added cost of installing a burner in there will be, but might be worth it .
Last edited by joe moving; 12-08-2016 at 11:47 AM..
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