Generator w/2 ACs - AC Shuts Down

[Lakejumper]

Hi, I’m running my 5500 Watt Onan gennie with two ACs on while driving due to very hot weather. They both ran for several hours and all of a sudden they shut down and the control panel beeped with the gennie still running. It eventually reset itself. This happened several times. We had a full tank of gas. I had the gennie serviced recently. Why is this happening?

[Bones2003]

Have you checked the oil level in the generator? Also, did it set any fault codes? You can download operator and service manuals by searching online that contain good troubleshooting information. They also explain how to check for and interpret the fault codes. You might check around the generator to see if the cover got reinstalled correctly and that nothing is blocking the airflow around it since it seems like the problem might be related to heat.

This is a long shot but with the generator off and not connected to shore power turn off your 12V disconnect switch (the salesman's switch) by the entry door for a few minutes. Sometimes just removing power allows the logic boards to reset and helps sort things out.

[Morich]

I would first want to decide which was giving me trouble. If the monitor beeps and the generator is still running, that would lead me to think it was not the generator.
So what does the manual say about the beeps? Is it a series of beeps to"decode" the error message?
I would think a check of the manual for what those beeps mean might be a first clue.

When you say it eventually reset itself, do you mean you did not look at the alarm to see what it was telling you? That can get us into a lot of trouble if we ignore warning signals!

Are you sure it was not the smoke detector you were hearing?

We need more precise info on what happened.

[creativepart]

I had this happen to me once recently, too. The generator never stopped running but the AC power seemed to reset. It, too, was when I was driving. I was near a place to stop and when I did the power came back on because the microwave chirped the way it does when power is applied. The A/C units took a while to restart because of the 5-min delay when resetting the units.

Because the power from the generator came back just as I stopped there was nothing to investigate. I have a generator switch on my dash that has a light. Sometimes when the generator is running as I drive if I'm forced to make a sudden stop or hit a very big drop or bump the generator will shut down. But I've never seen it restart all by itself. I have to restart it with the switch.

The power problem has not happened previously or since. So, I'm going to say all is fine until it does it again.

[Lakejumper]

Thank you for your replies. I think that I know what happened. I failed to mention that I was in the high Sierra mountains at about 6000-7200 feet when this occurred. I believe that the Power Management System did a “load shed”. The manual states that the AC’s use at least 2400 when starting up. I have a 15k btu in the front and either a 13.5k or 11k in the rear. The manual states that the 5500watt gennie loses 3.5% power for every 1000 feet gain in elevation.This, I was losing about 23% of the gennie power. It couldn’t keep up with the ACs.This has been a good lesson.

[jerichorick]

Originally Posted by Lakejumper

Hi, I’m running my 5500 Watt Onan gennie with two ACs on while driving due to very hot weather. They both ran for several hours and all of a sudden they shut down and the control panel beeped with the gennie still running. It eventually reset itself. This happened several times. We had a full tank of gas. I had the gennie serviced recently. Why is this happening?

I can think of a couple of things and I hope they pertain to your coach.

1/ can you adjust the shore power charge rate? This must be set to a low setting when on the generator.

2/ is your water heater ac switch on? This must be off when running on the generator. In both cases the EMS will see an overload and shut everything down to preserve the system. When on shore power there is enough available power to allow the EMS to shed loads on at a time. The generator power is so small in comparison it shuts everything off. After a period of time it brings things back on line.
This is only my theory. You can test this by watching your amp reading when running these things from the generator. You have only about 22A per leg available. When the HVAC units are running you have about 8 amps per leg to spare.