Community Forums

Quincy · 11-12-2017, 03:21 PM

Quote:

Originally Posted by manderson2228

I have a brand new Class A motorhome with the Onan generator. I have an intermittent/weird issue that i've worked with the dealer on and can't seem to find a resolution.

What happens is that the top breaker on my generator keeps tripping. However it only does it when I am driving. I can be setup all night in a parking lot running more things drawing more amps and its fine. I get out on the road and it trips 30 to 45 minutes in roughly and then I have no overhead AC while driving. We have replaced the breaker itself thinking it might be loose and nothing. They have also found that it wasn't wired correctly as it's 2 30A breakers. I am at a loss here as i've had it back to the dealer 5 or 6 times for this. Any help would be appreciated.

Can you be more specific about the "top breaker"? Is it possible you have something on the same circuit when travelling than when on shore power? Have you considered the possible difference in wiring between Gen and Shore power? (if there is any) I am wondering about the statement from the dealer that it was wired wrong. That usually translates to "I dont know what the problem is" Which, of course is obvious by now.

Speaking of,,, did you call the factory?

Quincy · 11-12-2017, 04:22 PM

Quote:

Originally Posted by manderson2228

Correct me if I was wrong but if there was a short that would be detected by that method it would've tripped inside the breaker box and not on the actual generator wouldn't it?

You are correct. Have you ever tried running the generator and the AC with the coach stationary to see if the breaker trips then?

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Quincy · 11-12-2017, 04:34 PM

I just scanned a thread where my question was answered, sorry. That puts the blame back on vibration from the road and back to a loose ground possibility. IMHO

twinboat · 11-12-2017, 05:01 PM

Quote:

Originally Posted by Quincy

I just scanned a thread where my question was answered, sorry. That puts the blame back on vibration from the road and back to a loose ground possibility. IMHO

A loose ground ?

The ground on a 120 volt system doesn't carry any current. You can cut it off and everything will still work.

It can be potentially unsafe, but still not going to trip a circuit breaker.

asuperheat · 11-12-2017, 05:16 PM

Quote:

Originally Posted by manderson2228

That is correct on when on generator and when moving. On shore power, or on generator while camping/stationary for the night it's fine all night.

That being said I personally would try the best I could to trace the wire from the genset to the transfer switch. It will be most likely either damaged insulation rubbing on the frame or chassis, also could be where someone was careless stripping back a wire and cut the insulation too much and left the conductor exposed touching the hot wire to the chassis, neutral wire or ground wire. In that case it would be close to a termination point or junction box. Look for signs of arching and a inspection mirror will probably help you see those hard to get to spots.

manderson2228 · 11-12-2017, 06:56 PM

Quote:

Originally Posted by twinboat

The OP definitely has a 50 amp service. You can see, in the transfer switch picture, a red " line 1 " a white neutral and a black " line 2 ". The green is ground and not switched.

Yes I have 50a and a 7k onan generator.

manderson2228 · 11-12-2017, 06:57 PM

Quote:

Originally Posted by Quincy

You are correct. Have you ever tried running the generator and the AC with the coach stationary to see if the breaker trips then?

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Yes in the original post or somewhere i dont remember now I can run fine all night no problem on generator stationary.

manderson2228 · 11-12-2017, 07:03 PM

So before I left the campground i checked all the square nuts inside the transfer switch and all were tight. Re-checked again and no obvious rubbing or arcing or anything loose.

That said just drove 8 hours and the circuit didn't trip. The only thing I can figure changed, was i moved around the wires in the junction box just to see everything, and it was cooler outside so the AC didn't run as much. a new data point or maybe just dumb luck. We were at disney and it is a magical place!!

Quincy · 11-13-2017, 03:30 AM

Quote:

Originally Posted by twinboat

A loose ground ?

The ground on a 120 volt system doesn't carry any current. You can cut it off and everything will still work.

It can be potentially unsafe, but still not going to trip a circuit breaker.

Respectfully, Most here, including me, are interchanging the words "ground and common" OPs system combines the two because it is a floating ground circuit. So the "loose ground" might be called "loose common" and if this is turning the compressor on and off my post below will apply.

Most here are not considering the load on the circuit. If the ground wire to the AC unit is opening and closing it will cause the compressor to start and stop. An AC compressor might not restart if that happens due to the pressure in the lines that must equalize somewhat before the comp. can restart, This causes the amp draw in the circuit to go up, allot. This alone can trip the breaker because the LRA (locked rotor amps) for the comp. is much more that the breaker can handle. If it were just a light going on and off the breaker would not be affected. The circuit itself wont trip the breaker, it is the load (in this case the AC) that can do that.

twinboat · 11-13-2017, 07:41 AM

Quote:

Originally Posted by Quincy

Respectfully, Most here, including me, are interchanging the words "ground and common" OPs system combines the two because it is a floating ground circuit. So the "loose ground" might be called "loose common" and if this is turning the compressor on and off my post below will apply.

Most here are not considering the load on the circuit. If the ground wire to the AC unit is opening and closing it will cause the compressor to start and stop. An AC compressor might not restart if that happens due to the pressure in the lines that must equalize somewhat before the comp. can restart, This causes the amp draw in the circuit to go up, allot. This alone can trip the breaker because the LRA (locked rotor amps) for the comp. is much more that the breaker can handle. If it were just a light going on and off the breaker would not be affected. The circuit itself wont trip the breaker, it is the load (in this case the AC) that can do that.

I'm sorry, but to call a Neutral conductor a ground or common ?, is not correct.

Quincy · 11-14-2017, 06:09 AM

Quote:

Originally Posted by twinboat

I'm sorry, but to call a Neutral conductor a ground or common ?, is not correct.

Of course it is, Anybody with any electrical knowledge will not be confused by the terminology. In the case of a Motorhome The ground and common are all the same so they can also be called the much less used term, neutral.

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aether_one · 11-14-2017, 06:20 AM

Quote:

Originally Posted by Quincy

Respectfully, Most here, including me, are interchanging the words "ground and common" OPs system combines the two because it is a floating ground circuit. So the "loose ground" might be called "loose common" and if this is turning the compressor on and off my post below will apply.

Most here are not considering the load on the circuit. If the ground wire to the AC unit is opening and closing it will cause the compressor to start and stop. An AC compressor might not restart if that happens due to the pressure in the lines that must equalize somewhat before the comp. can restart, This causes the amp draw in the circuit to go up, allot. This alone can trip the breaker because the LRA (locked rotor amps) for the comp. is much more that the breaker can handle. If it were just a light going on and off the breaker would not be affected. The circuit itself wont trip the breaker, it is the load (in this case the AC) that can do that.

But don't AC units have timers that prevent compressor restart for several minutes to prevent just this scenario? I know every AC I have ever owned has this feature.

sadtime · 11-14-2017, 07:16 AM

I had the same issue and replaced the main cable and socket. Problem solved. Turned out the plug was bad but you couldn't tell by looking at it.

Quincy · 11-15-2017, 03:57 AM

Quote:

Originally Posted by tfryman

But don't AC units have timers that prevent compressor restart for several minutes to prevent just this scenario? I know every AC I have ever owned has this feature.

Two things, or so... Timers on AC units did not used to be universally used. They may be now. There are two types of timers that I am familiar with. A "break on make" and a "break on break" timer. Translated, this means the timer breaks the circuit when the circuit makes or when the circuit breaks. The compressor is locked out for a few minutes either way if the circuit is "bumped". Unless there is something different nowadays these devices are installed in the low voltage wiring, in series with the red wire, which is the hot lead. I am not sure they will work correctly if the common wire is rapidly making and breaking the circuit. If the intermittent open is in the high voltage side of the compressor wiring then I doubt the timer would even know there is a problem. IMHO

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