About a 25 year old forced air gas furnace, the kind with an inducer
blower. No fancy electronics; just whatever kind of time delay they have
for the blower and an updated inducer control board also has a delay
circuit. So it's more a matter of wondering if the motors, gas valve, and
transformer will object to the perverted waveform of a "simulated sine
wave" inverter. I have a real generator so the inverter is more of a
backup to a backup. Thought I'd ask first.
I'm going to guess that the 24V transformer will have an output that's
closer to a real sine wave which lessens any unhappiness of the gas valve
and electronics so I suppose the transformer itself and the motors are the
items of concern.
Motors and solenoid valves are the least likely components to care about
the AC waveform. Both motors and solenoid valves are routinely operated
with PWM type drivers which produce waveforms much further from a sine
wave than a "MSW" stepped square wave inverter. As long as the inverter
is appropriately sized it should be fine.
You missed my point. I didn't say the motors or solenoid valves in your
furnace ran on PWM drives, I noted that motors and solenoid valves in
general are routinely operated on PWM drives. The motors and solenoid
valves in your furnace should be quite happy on MSW power.
That should be plenty for a residential sized furnace. You of course
need a hefty DC supply to power that inverter, presumably a vehicle
alternator. That will likely draw around 100A DC running the furnace.
Do you mean inverter that runs from a dc source and generates ac, or
do you mean a generator that runs from a gasoline-driven motor? A
2500 watt inverter would require humongous sized feeder cables if it
runs on 12V dc.
Not only big cables, but I saw reviews of several 12v cheapy
inverters, none could supply the rated watts, they were 10-15% off. So
if you have a 1000w inverter unit it may shut down as a 350w motor
pushes through its 850w needed startup surge. A 25 yr old furnace, its
motor is worn and could take well over 1200 startup surge, so a 2000w
inverter might work.
It's a Cobra CPI-2550 rated at 2500 W / 5000 W surge. (In the manual they
admit that 2500 is a one hour rating). I've tested it to about 1900 W with
resistive loads and some smaller inductive loads. (Meaning I plugged in an
air compressor because it was handy. It ran okay.)
I will likely never use it for the furnace since I have a generator but
it's good to have options.
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