Using solar generator to power Natural gas furnace

phdung

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Mar 14, 2022
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I am wondering if anyone has successfully used a solar generator like a Bluetti, or EcoFlow or whatever to power their Natural Gas (NG) furnace.
If so please give the make and model of generator.

FYI, I tried with my EB240, both with and without a neutrual grounding plug, it did not work, nor did it give any error codes.
 

BentleyJ

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When you say it didn't work, could you give more detail. A typical standard efficiency furnace has an induced draft motor/blower for combustion air movement through the burners and heat exchanger. That starts up first and if the negative pressure switch(s) close then the Igniter will turn on. Both of these items together would be in the 750Watt range or less. Once the gas valve opens and the flame starts the igniter shuts off and then the main blower will start usually within 30 seconds.
This is where I would expect you to have a problem. The inrush current on the main blower would certainly exceed 1000W at least momentarily.
Different brands of furnaces may have a different sequence of operation. If the main blower, inducer blower and igniter all come on together then the amperage is going to be too high.
High Efficiency furnaces usually have an ECM blower motor vs. the less expensive PSC motor. Since the ECM motors are essentially a version of variable frequency drive and ramp up to RPM there is a good chance this type would work with your EB240.
 
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phdung

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The initial fan would start (I'm guessing that is the induced draft motor you refer to)
Then I would get full flame
Then the watt guage on the EB240 would climb to about 950.
Then it would go back to 250 w or so.
Flames would stop.
But the main blower would never start.

I don't think the initial fan ever stops.
I lights the flame up again, then fails to start the main blower.

The weird thing is the EB240 never shuts down, it never throws an error code, it just cycles through over and over.

It's an old furnace, 30 years to be precise.
So I'm guessing it has a PSC motor.

I hope to have time this weekend to run it off the kill-a-watt meter to see what it actually pulls.
 

BentleyJ

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Sounds like the furnace is working OK but the EB240 just cannot start the blower motor. Does the Kill-A-Watt have a setting where it can capture the Peak Surge current? The initial inrush only lasts a couple hundred milliseconds, its hard to measure without a meter that has a "peak hold" function that will display the peak reading long enough to see it.
If you ever have the access door off the furnace the blower motor should have some electrical specs on it.
It is weird that the inverter doesn't throw an error code or beep or something.
 

time2roll

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Yes that old main blower is probably 1/3 to 1/2 hp and needs close to 1500-2000 watts to start. Those fans take a bit to spin up so it is more than a momentary surge.
Is the home breaker that feeds the unit 15 or 20 amps?
 

BentleyJ

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The furnace should have a dedicated breaker if the electrical system was done per customary standards. Otherwise the furnace outlet may just be one in a string of other outlets for the house. In either case it would be a 15 or 20A.
 

Nickatnyt

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My AC200P runs my Goodman gas furnace just fine, with a pull of 635 watts.

First I made a custom 3 wire electrical cord (standard extension with female end cut off). Then I shut the power off to the house (to replicate outage), then I isolated the furnace AND the digital thermostat from the junction box and wired in the extension cord with the appropriate wire nuts. Worked like a charm.
 

phdung

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Thank you BentleyJ for the suggestion of looking for a peak hold function.
However it has added some confusion.
First I noticed the meter was about 2 seconds behind the EB guage.
Meaning I'd hear the furnace spool, the EB guage would climb, and about 2 seconds later the kill-a-watt would read similar to the EB.

When using with the EB240 as a power source the highest the kill-a-watt "caught" was 880 w, however the EB read around 950 w.

When using a second home circuit as the power source. one trial the highest caught was also 880 w, but a second trial hit 1560 w.

That 1560 really surprised me because the furnace is on a dedicated 15 Amp circuit, so 1800 watt max.

At any rate at this point I'm leaning toward it pulling too many watts, but for such a short duration the kill-a-watt meter doesn't always "catch" the true high.
 

JimJr

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Thank you BentleyJ for the suggestion of looking for a peak hold function.
However it has added some confusion.
First I noticed the meter was about 2 seconds behind the EB guage.
Meaning I'd hear the furnace spool, the EB guage would climb, and about 2 seconds later the kill-a-watt would read similar to the EB.

When using with the EB240 as a power source the highest the kill-a-watt "caught" was 880 w, however the EB read around 950 w.

When using a second home circuit as the power source. one trial the highest caught was also 880 w, but a second trial hit 1560 w.

That 1560 really surprised me because the furnace is on a dedicated 15 Amp circuit, so 1800 watt max.

At any rate at this point I'm leaning toward it pulling too many watts, but for such a short duration the kill-a-watt meter doesn't always "catch" the true high.
The 15a circuit is a continuous 15a( @1800 watts ) , a 1/2hp motor continuous draw is @ 375 watts of the total 880 watts , but 5 x 375 =1875 watts during the start up cycle 1875 + ( 880 - 375 =505 ) = 2380 start up watts . Most HF inverters won't handle that being 1000w rated capacity .
 

A.Justice

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Fans are great candidates for soft starts, and the soft start units for fans tend to be much cheaper than ones for compressors as well.

I have an old 3/4 horse scroll fan that was salvaged from a heat pump running next to my wood stove for circulation. On full blast, the inrush is about 1500w, and it runs at 800w or so. With a cheap controller module, I keep the inrush below 800w. The one I have is more designed for speed control, but with a slight modification (or a different unit) it would eliminate inrush.

Edit: I don't own, or recommend this item, but it's generally what you would need to slow down that fan.

 
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