A/C and Generator

[lefoster]

Question........if I am using my generator and it runs out of gas while my A/C is running, does that hurt anything. Obviously the A/C will stop, but wondering if that damages anything.

[2018SLXBAJA]

No, I did that camping in Moab, UT we left to go on a white water rafting trip for 5-6 hours and needed the camper to stay cool for my dog. It ran most of 5-6 hours because it was dead when we got back and the camper was still cool.

[2edgesword]

Anytime a generator starts or shuts down voltage spikes occur that can damage sensitive electronics. As a normal practice you want the loads disconnected from the generator before starting it up or shutting it down. The start-up/shutdown procedure for many generators includes...

"Never start or stop the generator with electrical devices plugged in or turned on."

[Camper_bob]

The problem is that when the generator runs out of fuel, it doesn't just shut off suddenly. It will surge as it starts to suck the last bit of fuel to keep going. This surging causes wild fluctuations in the energy coming out of the genny. Those fluctuations (especially the low voltage ones) are a big problem for things like air conditioners, and can potentially cause damage. I would try to avoid a situation like that.

[ALJO]

The generator/converter will kick the bucket when under heavy load like an A/C, my son in-law went through 3 of them (hard learner). A normal generator doesn't but it isn't good for electronics present in RV's.

[lefoster]

thank you all for the replies. surges and spikes were my concern. the time it happened, we had gone to sleep with it running and it ran out sometime in the night. guess it would be best to cool things down and then shut it off before going to bed?

[ifallsguy]

With a hard wired EMS in place, as soon as it sees a voltage drop, surge, etc, it should cut off power. That's what it's designed to do. As long as it is set to prevent power past it for at least 2 minutes, I think you wouldn't harm anything in the trailer. The AC needs 2 minutes for pressures to equalize before restarting.

As for damage to the inverter, I think the fact the EMS would cut off any demand would put it in a no load situation and it shouldn't be damaged.

Just my opinion.

[2edgesword]

Originally Posted by ifallsguy

With a hard wired EMS in place, as soon as it sees a voltage drop, surge, etc, it should cut off power. That's what it's designed to do. As long as it is set to prevent power past it for at least 2 minutes, I think you wouldn't harm anything in the trailer. The AC needs 2 minutes for pressures to equalize before restarting.

As for damage to the inverter, I think the fact the EMS would cut off any demand would put it in a no load situation and it shouldn't be damaged.

Just my opinion.

This type of surge protection between the generator and RV would be a safeguard against electrical damage should the generator shut off unexpectedly.

[ifallsguy]

Originally Posted by 2edgesword

This type of surge protection between the generator and RV would be a safeguard against electrical damage should the generator shut off unexpectedly.

Thanks for adding that information. Forgot to put that into my comments.

Also the EMS would help protect against issues with shore power.

[bdreinv]

We ran out of gas twice on this trip still running, but will keep a closer eye on gas level! Thanks

[Camper_bob]

Absolutely, an EMS is a great idea for LOTS of other reasons. AND it would protect your equipment in this particular situation.

Something like this happened to us out on the road once. It was our first time overnighting at a WM on a long journey. I thought I could fire up the generator in the back of the pickup if I just opened one third of the tonneau cover. Turns out that wasn't enough ventilation and just about the time my head hit the pillow, the genny started overheating and surging. I could hear the A/C fluctuating and jumped out of bed and turned it off before any damage happened luckily. I was able to fully open the tonneau cover and drop the tailgate and the genny ran flawlessly for the rest of the night and the trip.

In our new MH, the tags were covering one of the vents on the generator, and caused it to overheat and begin surging in the same manner. Again, I popped up and turned off the AC units. I was able to clear that one up too and haven't had a problem since.

I really need to get my EMS before I break something!

[CampNow]

IMO . . . a non-inverter (typical open-frame) generator is much more likely (than an inverter generator) to introduce voltage and/or frequency deviations while the engine powers down down from a lack of fuel. I say that because an inverter generator's inverter circuitry is constantly monitoring/adjusting voltage, frequency, and checking the load at all times---purposely changing engine RPMs to accommodate changing loads. It's not unreasonable to expect an inverter generator's inverter circuitry to shutdown all output when it's unable to maintain proper voltage and frequency levels due to insufficient engine RPM. On the other hand, a non-inverter (open-frame) generator's voltage and frequency output is mechanically dependent on engine RPM--any change in engine RPM (i.e., surging and floundering while running out of fuel) instantly results in a change in voltage and frequency---not good.

As ifallsguy and Camper_bob also mentioned, an EMS should provide good protection. FYI, a "simple" RV surge protector, that typically costs $75-$125, offers little to no protection when a generator shuts down from a lack of fuel. A "simple" surge protector only provides protection from significant voltage spikes (a few milliseconds long) that result from lightning strikes or switching transients.

FWIW, we've run a Champion 3100 inverter generator out of fuel while powering some of our trailers with the a/c unit on many times---with and without an EMS. Never had any issues. Take this comment for what it's worth---a dime, maybe a quarter at most--lol! Don't know if we've been very lucky, or the inverter circuitry is actually doing an excellent job of blocking any voltage or frequency deviations from entering the trailer while the engine shuts down.

[Camper_bob]

Originally Posted by CampNow

IMO . . . a non-inverter (typical open-frame) generator is much more likely (than an inverter generator) to introduce voltage and/or frequency deviations while the engine powers down down from a lack of fuel. I say that because an inverter generator's inverter circuitry is constantly monitoring/adjusting voltage, frequency, and checking the load at all times---purposely changing engine RPMs to accommodate changing loads. It's not unreasonable to expect an inverter generator's inverter circuitry to shutdown all output when it's unable to maintain proper voltage and frequency levels due to insufficient engine RPM. On the other hand, a non-inverter (open-frame) generator's voltage and frequency output is mechanically dependent on engine RPM--any change in engine RPM (i.e., surging and floundering while running out of fuel) instantly results in a change in voltage and frequency---not good.

As ifallsguy and Camper_bob also mentioned, an EMS should provide good protection. FYI, a "simple" RV surge protector, that typically costs $75-$125, offers little to no protection when a generator shuts down from a lack of fuel. A "simple" surge protector only provides protection from significant voltage spikes (a few milliseconds long) that result from lightning strikes or switching transients.

FWIW, we've run a Champion 3100 inverter generator out of fuel while powering some of our trailers with the a/c unit on many times---with and without an EMS. Never had any issues. Take this comment for what it's worth---a dime, maybe a quarter at most--lol! Don't know if we've been very lucky, or the inverter circuitry is actually doing an excellent job of blocking any voltage or frequency deviations from entering the trailer while the engine shuts down.

Good point. The generator I used with the TT was a Champion open frame generator. The one in the motorhome is an Onan 4kw; I'm guessing it's not an inverter generator. When it went into overheating, there were definite fluctuations in the power.