Gas and Oil Home Heating Furnaces - Inverter for furnace blower
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OhioSteve
01-16-09, 05:52 PM
Wondering if this can be done. I have a 2000 watt, (12 volt battery is the source) inverter. I want to know if I could wire this up to my Gas furnace's SPST switch and use it when the power goes out. What I'm thinking is either a 3-way switch in place of the SPST, or some sort of A/B switch. If the main power goes out, I'd like to keep the furnace going by switching over to the inverter. Since it would not be true A/C voltage, would I fry the circuit board if I switched over to the inverter? I'd have the main power leg, the inverter power leg, and the leg going to my furnace. Seems it should run a fractional HP motor, but not sure what you guys think, or if it is even plausable? Thanks
xpogi
01-16-09, 07:23 PM
...Since it would not be true A/C voltage...
Not sure what you mean by not being "true A/C". Does the inverter work OK with other electronic devices like televisions and computers? If that is the case I don't see why it would fry your furnace's control board.
But you furnace could fry your inverter. Are you sure 2000 watts is enough? Most furnaces require a 20 AMP circuit which would be roughly 2300 watts. It wouldn't draw that much all the time but could very likely draw that much for a fraction of second when the blower first switched on.
About the switch. You wold need a double poll double throw switch. You would definitely need a break before make switch or things could get harry! One of those old fashioned knife switches like you see the executioner use to switch power to "old sparky" would work fine if you could find one. Just make sure you enclose it in a tamper proof box so no one's hands get across the terminals.
Not sure what you mean by not being "true A/C". Does the inverter work OK with other electronic devices like televisions and computers? If that is the case I don't see why it would fry your furnace's control board.
But you furnace could fry your inverter. Are you sure 2000 watts is enough? Most furnaces require a 20 AMP circuit which would be roughly 2300 watts. It wouldn't draw that much all the time but could very likely draw that much for a fraction of second when the blower first switched on.
About the switch. You wold need a double poll double throw switch. You would definitely need a break before make switch or things could get harry! One of those old fashioned knife switches like you see the executioner use to switch power to "old sparky" would work fine if you could find one. Just make sure you enclose it in a tamper proof box so no one's hands get across the terminals.
SeattlePioneer
01-16-09, 09:35 PM
A furnace takes quite a bit of power to operate, mostly due to the fan. 700 watts might be typical, but the power consumption of your furnace can be found on the furnace rating plate near the burner compartment.
700 watts @ 12 volts is 58 amps. I don't think your battery would last very long.
A motor generator would be a better bet for that kind of service.
Personally I have a wood stove as an alternative source of heat and have a couple of propane lanterns I can hang on hooks screwed into ceiling joists about the house. Plus I have a natural gas stove, with a propane camp stove available.
I had a power outage for six hours or so ago just a few weeks ago --- that system worked very well.
I also have a propane catalytic camp heater I can fire up off a tank of propane. That's a little riskier since it's unvented equipment, but I happen to have a CO detector from my days as a furnace repairman, so I can check it out.
700 watts @ 12 volts is 58 amps. I don't think your battery would last very long.
A motor generator would be a better bet for that kind of service.
Personally I have a wood stove as an alternative source of heat and have a couple of propane lanterns I can hang on hooks screwed into ceiling joists about the house. Plus I have a natural gas stove, with a propane camp stove available.
I had a power outage for six hours or so ago just a few weeks ago --- that system worked very well.
I also have a propane catalytic camp heater I can fire up off a tank of propane. That's a little riskier since it's unvented equipment, but I happen to have a CO detector from my days as a furnace repairman, so I can check it out.
thermofridge
01-16-09, 10:52 PM
Lets redo the math. You have a 2000 watt inverter. At 120V that will give you 16.6 amps. Ohms law...watts/volts = amps. Every gas furnace Ive installed has a max circuit of 15 amps. The total running amps of most furnaces is usually between 5 and 9 amps. Your 2000 watt inverter should be big enough. There is however the issue of grounding. Since I have no experience with one of these setups, Im not sure if the flame sensor will work on an inverter. You will just have to try it.