Gas Backup power didn't back us up!

[Jack Murdock]

if the furnace and water heater are fairly new they probably have hot surface or intermittent ignition systems. Those require a good ground to operate and the correct polarity and good clean power. Without a good clean power they will not ignite. If no ignition the gas valves will not open.

 

[Pilot]

if the furnace and water heater are fairly new they probably have hot surface or intermittent ignition systems. Those require a good ground to operate and the correct polarity and good clean power. Without a good clean power they will not ignite. If no ignition the gas valves will not open.

To clarify:
"Regulator froze up" Temp was about 30 degrees. Was windy, but only about 4 or 5 mph. If that was the culprit, why would both furnace & water heater come back on immediately when power came on and continue with no problems? No delay, both started working right away as soon as power came on.

We had lights on & wife cooked dinner on the microwave.

Gas is propane, tank was 55% full.

Cable runs from generator to transfer switch.

Generator is gasoline fueled, rated at 7000 watts. Runs well, freezer, furnace fan, microwave, some lights (LED's).

When power failed lights flashed repeatedly for maybe 30 seconds. Didn't kill computers or anything else.

Thanks to all who replied, I'm hoping for more suggestions.

 

[MossRoad]

To clarify:
"Regulator froze up" Temp was about 30 degrees. Was windy, but only about 4 or 5 mph. If that was the culprit, why would both furnace & water heater come back on immediately when power came on and continue with no problems? No delay, both started working right away as soon as power came on.

We had lights on & wife cooked dinner on the microwave.

Gas is propane, tank was 55% full.

Cable runs from generator to transfer switch.

Generator is gasoline fueled, rated at 7000 watts. Runs well, freezer, furnace fan, microwave, some lights (LED's).

When power failed lights flashed repeatedly for maybe 30 seconds. Didn't kill computers or anything else.

Thanks to all who replied, I'm hoping for more suggestions.

Good info. That kills the theory that the generator is drawing too much propane for the furnace and water heater to work, because the generator doesn't draw any propane at all.

So that probably means it's an electrical issue. Continue troubleshooting from that point.

You also said that this setup has worked in the past, but didn't work this time. That would indicate something has changed electrically, or something has failed electrically.

 

[jwinner]

I'm going to guess it has to do with your neutral. Generators either have a floating neutral, or a bonded neutral. That is, on the generator outlet, a bonded neutral will be connected to the ground terminal on the outlet. On a floating neutral, it is not. I don't understand the implications or why behind it. I've heard gas furnaces not functioning properly with a floating neutral, and the solution is to make an adapter that bonds the neutral and ground. Some googling may be in order and should help you decide if that is your issue.

 

[drssg]

I'll be interested to see if this mystery is solved. Our gas hot water heater doesn't even have an electrical connection.

If the OP's is that way, it seems like something is somehow shutting off the gas supply?

 

[Industrial Toys]

One word..... Murphy. Why would it work when you really needed it? Sounds like lack of fuel from the limited information, yeah, like the regulator.

 

[Pilot]

One word..... Murphy. Why would it work when you really needed it? Sounds like lack of fuel from the limited information, yeah, like the regulator.

What seemed a crackpot answer may be the right answer, the regulator!

Looking online about regulators freezing up it seems that regulators do freeze up. I don't understand the dynamics as the explanation wasn't clear to my 76 year old brain, but if the answer truly is a frozen regulator it seems it is related to gas pressures and evaporative cooling. Anyway a frozen regulator might explain why both systems came back on at the roughly same time the power was restored, if, for example, the furnace started drawing juice allowing the regulator to defrost and the water heater to fire up. I dunno. Maybe someone who knows this stuff can offer a better explanation.

I love TBN!

 

[dodge man]

Most furnaces and gas water heaters have an ignitor, not a pilot light any more so hence the need for electricity to light them up.

 

[CobyRupert]

I'm going to guess it has to do with your neutral. Generators either have a floating neutral, or a bonded neutral. That is, on the generator outlet, a bonded neutral will be connected to the ground terminal on the outlet. On a floating neutral, it is not. I don't understand the implications or why behind it. I've heard gas furnaces not functioning properly with a floating neutral, and the solution is to make an adapter that bonds the neutral and ground. Some googling may be in order and should help you decide if that is your issue.

Regarding generators and neutrals: It comes down to the transfer switch (if you even have one). This determines if the neutral and ground need to be bonded at the genny.
Neutral & ground should only be bonded at one location. This is typically in your main panel. This typically doesn't change when the genny supplies the panel.
I guess 99% of most residential transfer switches do not have a switched neutral, thus the ground and neutral should not be bonded (connected at the genny) or at any adapters or connections between the genny and your electrical panel. Genny connections that don't use a transfer switch, but use a back-feed circuit should also not have their ground and neutral bonded at the genny.

Even if N & G are incorrectly bonded at genny, not sure why furnace and water heater didn't fire. Maybe as JackMurdock noted, ignition controls are sensitive?
Otherwise, did you have all the normal circuits you usually have? (i.e. Or did you only have 1/2 of your normal 120V (i.e. a single leg)? Did you have any 240V loads operate correctly?

 

[CADplans]

Anyway a frozen regulator might explain why both systems came back on at the roughly same time the power was restored,
if, for example, the furnace started drawing juice allowing the regulator to defrost and the water heater to fire up.

The regulator should be located in an outdoor location,,
sometimes when they "freeze" the regulator will simply continuously vent propane gas to the atmosphere,,,