----- Original Message -----
From: <subscriptions aeolusdevelopment com>
To: <elec-trak cosmos phy tufts edu>
Sent: Tuesday, December 11, 2007 10:33 AM
Subject: Re: (ET) Power Inverters
Bill Alburty Wrote
Every winter, when there is an impending ice storm, I begin to wonder if
there is a way to use the 36 VDC power source of my ET battery pack to
operate my gas furnace for a day or two, since the gas is still
available. Those of you who have used ET power inverters for this
purpose could tell us how much wattage you can get from fully charged ET
batteries, and for how long. It would have to supply about 11 AC amps at
115 VAC/60 Hz to run the blower and gas valve. At a reduced
house-thermostat setting, it seems to me that maybe enough heat could be
circulated to get through two day's power outage.
Back of the envelope
- 11A at 115V --> 36A at 36V
Gives about 3 hours on a 100Ah battery. Real world efficiencies will make
it slightly worse. ET batteries are what? about 120Ah to 150Ah? So maybe
3-4 hours of continuous operation. Duty cycle is obviously important.
Is there a good simple design out there for making a 60 Hz inverter?
Buy it. I seem to remember PowerStream having something. The trouble is
36V is an odd voltage. Although reasonably common for North American
forklifts most backup voltages are either 48V or 24V so inverters are more
common at those voltages.
Does anyone know if the 24 VAC furnace gas valve will operate on DC?
Maybe but 24VAC will give a higher voltage than a 24VDC tap. I wouldn't
be
tempted to even try. It may void your warranty, I expect it'll void your
insurance.
Robert
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