Continued from Page 9
electronics. The inverter you mentioned in
your email most likely has plenty of power
to start and run your furnace. Some
considerations about inverters are:
1. Zero or no-load power consumption. In other words, how much power
does this inverter draw from a battery
when it is simply "on" and not carrying a
load. Less expensive inverters will draw
anywhere from one-half to one amp of
standby current, so if you leave it
permanently connected to a battery, it
will eventually draw the battery down to
nothing unless you are charging it with a
charger capable of supplying more than
that current. Of course, you can simply disconnect the inverter from the battery when
it is not in use to eliminate this problem.
2. Sine wave or modified square wave
output. Less expensive inverters employ a
digitally-generated approximation of a sine
wave at the output. Most AC fan motors are
inductive motors and may be particular
about the "quality" of the power they
receive, especially when starting up. My
general experience is that inverters made
today are good enough to start even the
most picky inductive motors, provided you
have enough headroom in the power rating
of the inverter you choose. A general rule-of-thumb is if you choose an inverter rated
for 200% or more of the motor's power rating, it will probably start reliably. Fan motors
have a fairly limited load on them (usually a
squirrel cage fan) and are easier to start than
say, a refrigerator or air-conditioner motor.
3. Battery life. You want your battery
to be available and up-to-snuff when you
eventually need it. This requires putting a
quality charger on it — one with a fully
automatic cutoff — and you will need to
occasionally check on it to make sure
everything is working properly and the
water levels are correct, etc.
So, in the end, you should find yourself a decent battery charger, deep-cycle
battery, and inverter, and with the breakout
box I described in the article, you should
be able to switch over to battery power on
your furnace in less than 10 minutes. I
would not recommend leaving the furnace
on the inverter as a permanent installation,
as this may be hard on your battery, inverter, and possibly your furnace fan motor(s).
I will consider a separate article on
Email: email@example.com or
USA Office: Blink Manufacturing 14019 Whispering Palms Dr.
Houston, TX 77066, PH. 281-397-8101 FAX: 281-397-6220
Mexico Plant: Automatizacion, Ensambles Y Cir. Impresos, S.A.C.V.
Alamo 93, 4o. Piso, Sta. Mónica, Tlalnepantla, Edo. de México 54040
PH: 011 52-555 360-3648 & 011 52 555-361-3351
FAX: 011 52-555 361-5996
inverters for the future — thanks for the
Kenton Chun KE4IEF
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June 2007 45