Re: (ET) Power Inverters

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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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