[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

(ET) Power Inverters - cold batteries, motor current draw


1) Check the size of your Furnace motor - calculate the actual current
draw - Or, better yet- buy a 'Kill-A-Watt' meter on EBay (I paid about $23
plus shipping of a few $$).
[Of course, you have to pull the AC line from your Power Panel, and install a plug, but you will get a good wattage number - both while fan motor is on, and when not - but thermostat transformer sill powered]
2) if 1 hp motor (AC) is about 750 watts, and your furnace blower is 1/4 hp, 
then 1/4 * 750 = 187.5. or, say, roughly a couple amps - say 3 just to be
safe.
So, if the other calculation is correct - at approx 11 amps for about 3
hours, you might get 3.6 times the hours at only 3 amp draw = 11 hours.
Now, factor in that you might be able to run furnace only 15 minutes eery
hour, so you get 4 times that, or 44 hours.
Of course, the control circuit - gas valve - draws a little power also, but
that gets power from 24VAC transformer which should work great from a sine
wave inverter.  Also, you could have a separate inverter (12V car battery
powered, maybe) just to run the gas valve & control circuit transformer.

3) batteries might put out less of their energy in cold weather.

4) if you need to run lights, use LED's.  They draw TINY amounts of power,
and will work in a frozen garage/shop (unlike my flourescent bulbs, which
want 50 or 60 degrees F to start !)
Regular incandescent bulbs will eat that battery energy, that you need for
turning your furnace blower motor.
----- 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


--------------------------------------------------------------------
mail2web.com - Enhanced email for the mobile individual based on Microsoft® 
Exchange - http://link.mail2web.com/Personal/EnhancedEmail



_______________________________________________
Elec-trak mailing list
Elec-trak cosmos phy tufts edu
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak


__________ NOD32 2716 (20071211) Information __________

This message was checked by NOD32 antivirus system.
http://www.eset.com