A/C on generator question

[DelawareRick]

I'm new to the forum and, well, fairly new to the RV world but hope someone can help me understand something. (And I've done a good bit of research via Google, but still haven't found a straight answer that I could understand. That's why I'm posting here.)

First, my rig:
2006 Thor Hurricane 33H
Onan RV Marquis Gold 5500 generator w/about 1000 hours on it
Two 13,500 BTU air conditioners


My questions:
1. Should I be able to run both air conditioners simultaneously using my generator?
2. When I try to run both ACs on generator, the 20 amp breaker on the generator trips. I guess my question is, why not the 30 amp breaker on the generator? (I would think the ACs would/should be connected to the generator via the "bigger" breaker, but maybe I'm just completely backwards in that thinking.)
3. If the generator has nothing drawing power (because its breaker has tripped) would it shut down "on purpose"? Mine did yesterday, about 15 minutes after the AC tripped the breaker. I'm trying to determine if this indicates a problem, a fluke, or is "working as intended".

Thanks in advance for your help.

Rick

[DelawareRick]

Gjac - No, I'm just talking about on generator issues.

dougrainer wrote:
They both stopped working (also NO 120 power to the RV) because in your system, the 120 volt transfer box has 2 120 inputs from the Genset. BOTH Inputs must have 120 power to close the switch and power the RV. I still think you have a defective AC. probably the rear AC if you state you can run 1 AC and I assume that is the front one. Kill the AC that is running fine. Turn the other AC ON and see if it will run more than your 45 minutes to an Hour without tripping the breaker. Also, we need to know year/Brand/Model of RV. Do you have an Inverter/Charger? If so, that may be your problem. Years ago when they installed 5.5 or 6.5 Onan Gensets, they wired the Rear AC and the Inverter/Charger on the 2nd leg of the Genset. 6.5 onans had 2-30 amp breakers. 5.5 have the 30 and the 20. When the Power(120) is first applied to the RV, The Inverter/Charger goes into BULK charge mode and if the Internal charge rate has not been changed from the Inverter maker settings, THAT 12 volt charge rate will pull up to 10 amps. That means if you have the rear AC running and since you just started the Genset, that 20 amp breaker will have the rear AC(11 to 14 amps) PLUS the Inverter/charger at 10 amps which will be OVER the 20 amp threshold of the Onan breaker and will trip. When IT trips, the 120 Transfer kicks out. Also, If you do NOT have an Inverter/Charger, there may be some other hi amp appliances pulling current on that leg going over the 20 amp threshold. If you have the Inverter/Charger, the fix is to reset its bulk charge rate to a lower amp draw around 3 to 5 amps(AC amps not DC amps). Doug

It's a 2006 Thor Hurricane 33H. It does not appear that I have an inverter. (The manual describes the appearance and location of a remote switch for it, which I don't have. And it's my understanding an inverter would be close to the coach batteries, and I don't see anything that looks like an inverter. Apparently this was an option on the Thor.)

The only other thing I know of that is on is the fridge. I've verified that the water heater is not on, and water pump is not on.

I'll try running the rear AC for a while to see if it trips the CB. Thanks again for all your help.

[dougrainer]

DelawareRick wrote:
I swapped black wires back to original locations, then ran both ACs. Both ran fine for at least, say, 45 minutes at which point I started tripping generator CBs to verify behavior. It is still the case that if either generator CB is off, neither AC will work.

At this point it's sort of academic... since we can make due with 1 AC while on generator, I'll probably just stick to running one rather than risk an issue running both. I'd just like to have an understanding of why both ACs stop working.

They both stopped working (also NO 120 power to the RV) because in your system, the 120 volt transfer box has 2 120 inputs from the Genset. BOTH Inputs must have 120 power to close the switch and power the RV. I still think you have a defective AC. probably the rear AC if you state you can run 1 AC and I assume that is the front one. Kill the AC that is running fine. Turn the other AC ON and see if it will run more than your 45 minutes to an Hour without tripping the breaker. Also, we need to know year/Brand/Model of RV. Do you have an Inverter/Charger? If so, that may be your problem. Years ago when they installed 5.5 or 6.5 Onan Gensets, they wired the Rear AC and the Inverter/Charger on the 2nd leg of the Genset. 6.5 onans had 2-30 amp breakers. 5.5 have the 30 and the 20. When the Power(120) is first applied to the RV, The Inverter/Charger goes into BULK charge mode and if the Internal charge rate has not been changed from the Inverter maker settings, THAT 12 volt charge rate will pull up to 10 amps. That means if you have the rear AC running and since you just started the Genset, that 20 amp breaker will have the rear AC(11 to 14 amps) PLUS the Inverter/charger at 10 amps which will be OVER the 20 amp threshold of the Onan breaker and will trip. When IT trips, the 120 Transfer kicks out. Also, If you do NOT have an Inverter/Charger, there may be some other hi amp appliances pulling current on that leg going over the 20 amp threshold. If you have the Inverter/Charger, the fix is to reset its bulk charge rate to a lower amp draw around 3 to 5 amps(AC amps not DC amps). Doug

[Gjac]

Electrical stuff is not my strong suit, so maybe I am missing something basic, but if I understand your post correctly you are trying to run 2 AC's on regular house current from a standard 15 amp wall outlet(2 parallel prongs and a ground) and not in a CG with 50 amp service, is that correct? If that is the case 15 amps is not enough to power 2 AC's. Mine would always trip from the std house plug before I installed a 50 amp wall outlet.

[joebedford]

I still think it's because somebody put both ACs on one leg of the generator (look at coach breakers NOT generator breakers).

Neither AC (or any other a/c stuff) will work with one generator breaker off because your transfer switch won't, well, transfer.

[DelawareRick]

I swapped black wires back to original locations, then ran both ACs. Both ran fine for at least, say, 45 minutes at which point I started tripping generator CBs to verify behavior. It is still the case that if either generator CB is off, neither AC will work.

At this point it's sort of academic... since we can make due with 1 AC while on generator, I'll probably just stick to running one rather than risk an issue running both. I'd just like to have an understanding of why both ACs stop working.

[DelawareRick]

joebedford wrote:
OK, now that we know your rig is 50A, the first thing to do is make sure one AC is on one side of your breaker panel (genset leg) and the other AC is on the other side (genset leg).

If they're both on the same side, it will give exactly the symptoms you describe.

The reason it will work on shore power is because each leg gets 50A as opposed to on genset when it gets only 20A or 30A.

Thanks Joe. Once I've done this other troubleshooting, maybe it will become clear if they are on separate generator CBs...

[DelawareRick]

CA Traveler wrote:
Again you've got to fix the DC problem first, ie the light problem. Many controllers use DC including A/Cs and won't operate without DC. The outlets indicate they are now on the 30A CB as expected.

I suspect that someone has changed/modified your rig wiring/equipment beyond what you've just found. Given what you've posted it's strange that you have lights except when a gen CB is tripped. Also the gen should continue to run with CBs tripped.

Double check: The lights are OK w/o gen or shore power indicating at least some battery power, correct?

Given what you've posted I'm not surprised that you haven't gotten "straight answers".

Thanks CA Traveler. Lights are fine on battery, and on shore power. They're fine on generator UNTIL either generator CB trips. The generator does continue to run with either or both CBs tripped. (Not withstanding the one time I saw the generator stop. I ran it several hours yesterday with CBs in various states and it never stopped running.)

dougrainer wrote:
Yes, he should have 12 volt lights in the RV, But, That will not cause his Genset breaker tripping problem. The Black/yellow stripe Genset wires designate which is 20 and 30 amp wire feed If you look on those 2 wires you will see a 20 and a 30 on the appropriate wire. That is an Onan color code. Since you have 50 amp service, it takes BOTH the 20 and 30 amp breaker to engage the Auto transfer box. I assumed you had a 30 amp service RV, which my post was correct on for a 30 amp RV with a 5500 genset. Now, at this point go back and reverse the black wires on the Genset feed to get it back to Factory spec. Make sure everything 120 is OFF and run the Genset and then run just both AC units. IF the 20 amp breaker still trips, I would suspect you have a rear AC that is defective and the compressor is pulling too many amps. IF SO, connect to 50 amp service and run the AC units, IF the rear AC trips ITS 20 amp breaker in your main breaker panel, you have a problem with that AC unit. If you had your unit in my shop, the FIRST thing I would do is a performance/AMP check of the Rear AC to see if it is operating to spec. If Good, then I would trace the reason the the amp draw tripping the breaker which may be the Front AC which I would also Performance/Amp check, to rule out both AC units. Doug

Thanks Doug. I will put the wires back to their original state and do as you've stated. (I didn't see the 20 or 30 on the wires though it may have been there and I missed it. They said "cb1-load" and "cb2-load" though.)

I may not be able to connect to a 50 amp service since I'm at home now and only have access to regular household outlets. (15 amps? 20?) Regardless, I'll do what troubleshooting I can.

[CA_Traveler]

It appears that he has multiple problems.

[joebedford]

OK, now that we know your rig is 50A, the first thing to do is make sure one AC is on one side of your breaker panel (genset leg) and the other AC is on the other side (genset leg).

If they're both on the same side, it will give exactly the symptoms you describe.

The reason it will work on shore power is because each leg gets 50A as opposed to on genset when it gets only 20A or 30A.

[dougrainer]

CA Traveler wrote:
Again you've got to fix the DC problem first, ie the light problem. Many controllers use DC including A/Cs and won't operate without DC. The outlets indicate they are now on the 30A CB as expected.

I suspect that someone has changed/modified your rig wiring/equipment beyond what you've just found. Given what you've posted it's strange that you have lights except when a gen CB is tripped. Also the gen should continue to run with CBs tripped.

Double check: The lights are OK w/o gen or shore power indicating at least some battery power, correct?

Given what you've posted I'm not surprised that you haven't gotten "straight answers".

Yes, he should have 12 volt lights in the RV, But, That will not cause his Genset breaker tripping problem. The Black/yellow stripe Genset wires designate which is 20 and 30 amp wire feed If you look on those 2 wires you will see a 20 and a 30 on the appropriate wire. That is an Onan color code. Since you have 50 amp service, it takes BOTH the 20 and 30 amp breaker to engage the Auto transfer box. I assumed you had a 30 amp service RV, which my post was correct on for a 30 amp RV with a 5500 genset. Now, at this point go back and reverse the black wires on the Genset feed to get it back to Factory spec. Make sure everything 120 is OFF and run the Genset and then run just both AC units. IF the 20 amp breaker still trips, I would suspect you have a rear AC that is defective and the compressor is pulling too many amps. IF SO, connect to 50 amp service and run the AC units, IF the rear AC trips ITS 20 amp breaker in your main breaker panel, you have a problem with that AC unit. If you had your unit in my shop, the FIRST thing I would do is a performance/AMP check of the Rear AC to see if it is operating to spec. If Good, then I would trace the reason the the amp draw tripping the breaker which may be the Front AC which I would also Performance/Amp check, to rule out both AC units. Doug

[CA_Traveler]

Again you've got to fix the DC problem first, ie the light problem. Many controllers use DC including A/Cs and won't operate without DC. The outlets indicate they are now on the 30A CB as expected.

I suspect that someone has changed/modified your rig wiring/equipment beyond what you've just found. Given what you've posted it's strange that you have lights except when a gen CB is tripped. Also the gen should continue to run with CBs tripped.

Double check: The lights are OK w/o gen or shore power indicating at least some battery power, correct?

Given what you've posted I'm not surprised that you haven't gotten "straight answers".

[DelawareRick]

The MH is 50 amp.

Doug - I swapped the black cables (though one was actually black/yellow, which gave me pause. I researched, then felt comfortable swapping them). I then repeated my troubleshooting:

With only 20 amp CB off:
Both AC OFF
All outlets ON
All lights OFF

With only 30 amp CB off:
Both AC OFF
All outlets OFF
All lights OFF

When I try to run both AC at the same time, the 20 amp CB trips, which is what it was doing before.

Doesn't seem like each AC has its own generator CB, unless I'm misunderstanding things. Otherwise one would work if at least one CB was on, right?

[j-d]

DelawareRick wrote:
Thanks for the replies so far everyone - they've certainly helped me understand this better. Or at least I think so.

dahkota - Water heater is off.

dclark - Neither AC runs if EITHER generator CB is off (see my troubleshooting steps below)

dougrainer - Your info was particularly useful. I did some troubleshooting and found the following:
***NOT SHOUTING, JUST WANT TO SET MY COMMENTS APART FROM YOUR TEXT***
With only 20 amp generator CB off: BUT THE 30A IS ON?
Both AC units have no power
All outlets have NO power SUGGESTS DOUG'S COMMENT OF LOADS REVERSED IS THE CORRECT ANSWER
No coach lights
Slide does work

With only 30 amp generator CB off: BUT THE 20A IS ON?
Both AC units have no power ***NO*** POWER??? YOUR FIRST STATEMENT SOUNDS LIKE BOTH WERE TRYING TO RUN ON THE 20A SIDE OF YOUR ONAN! TYPO HERE???
All outlets have power PER DOUG'S COMMENT, SEEMS MOST OF THE COACH IS CONNECTED TO THE 20A SIDE OF YOUR ONAN
No coach lights
Slide does work

Possibly unrelated: When one of the generator CBs is off (I forget which one) the "levels" button works and shows me tank, propane, etc levels. When the other CB is off, it doesn't. I only mention it because I wondered if power is being turned off to the thermostat (since it's in the same overall control panel) and that could be causing a problem. Again... new guy here... so might be completely off course.

IS THIS A 30A OR 50A? HOW MANY PRONGS ON YOUR SHORE TIE CABLE WHERE IT PLUGS IN AT THE CAMPSITE? 03 PRONGS MEANS 30A, 04 PRONGS MEANS 50A.

I'VE SEEN 30A COACHES WITH 5500 GENNYS. THE 30A SIDE OF THE GENNY TAKES OVER ALL BUT THE SECOND A/C AND THAT'S HANDLED BY THE 20A SIDE. THAT MEANS YOU CAN RUN BOTH ON GENNY BUT NOT ON 30A CAMPGROUND PEDESTAL POWER. WHICH IS WHY THERE MAY BE A FRONT/REAR SELECT SWITCH, ONLY FOR A/C.

TO RUN ON GENERATOR, DO YOU HAVE TO PLUG YOUR SHORE TIE INTO A CAMPGROUND PEDESTAL-STYLE SOCKET? I'M THINKING THAT ON CLASS A, PROBABLY NOT, YOU HAVE AN AUTOMATIC TRANSFER SWITCH. GENNY COMES ON LINE, ATS DISCONNECTS SHORE TIE CABLE AND POWERS COACH FROM GENNY. IF YOU HAVE AN ATS, AND ITS CONTROL VOLTAGE IS COMING OFF THE 20A SIDE AS DOUG SUSPECTS, YOU WOULD NEED BOTH 20 AND 30 ON TO SEE POWER THROUGHOUT THE COACH. ONLY PROBLEM, AS DOUG SAID, THE LOAD YOUR COACH DRAWS IS BEING SUPPLIED OFF THE WRONG (20A) SIDE OF YOUR ONAN.

[wwest]

Those A/C's will draw about 10 amps each with the compressor running.

Startup of the compressor will require as much as 25 amps, >30 amps for a short off cycle restart of the compressor.

You genset likely can not support starting, restarting both compressors roughly simultaneously.