Electrical Issue

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The only thing that explains the latest set of symptoms as described is that the generator's own circuit breaker has tripped OR somehow the transfer switch failed when the load increased (a/c turned on). The question is, why does the a/c load do that when on the generator but not on shore power?

However, when coupling this last episode to the earlier failure, which apparently was reset by using the battery disconnect, this gets very confusing.  The two sets of symptoms are inconsistent and I think it is going to take very methodical diagnostic procedure to isolate the problem. My guess is the battery disconnect rest is coincidence and something else actually reset the first set of problems, but that's just a guess without carefully re-testing everything.
 
The question is, why does the a/c load do that when on the generator but not on shore power?
Click to expand...

Some transfer switches use a non-latching relay that's energized when the generator is running.  If the generator voltage drops due to the starting surge of the air conditioner, the relay can drop out and revert to the shore power position.
 
Lou Schneider said:
Some transfer switches use a non-latching relay that's energized when the generator is running.   If the generator voltage drops due to the starting surge of the air conditioner, the relay can drop out and revert to the shore power position.
Click to expand...

Lou, I'm not aware of any transfer switch that uses a mechanical latching technique.  I think they are all mostly held energized by just the generator voltage.  If they dropped out, wouldn't they immediately try to re-energize if the generator was still running?

I'm still (since the original post) betting on a faulty transfer switch.  Several scenarios could be built around faulty contacts, pick coil and/or hold coil failures.  Of course, a failure at the generator output could appear the same.  The findings and cost of diagnosis and repair will be interesting.
 
My Magnetek transfer switch uses a 3 pole, 30 amp contactor.  The third pole provides an electrical latch for the relay coil.  Pull-in is via a time delay that lets the generator come up to speed and stabilize before switching the load to it.

I haven't tested it's failure modes, but I could imagine the pull-in logic being a one-shot that releases once the contactor pulls in and doesn't reset until all power is removed from the switch.  This would prevent relay clatter while on the generator - once the relay drops out it stays out until the logic is reset.
 
Lou, your TX switch sounds pretty standard.  The Iota, PD, Go-Power and others all use basically the same contactor.  The generator is typically wired to the override side which, as you said, provides a time delay to allow the gen to come up to speed.

Like you, I don't have a diagram of the actual energizing and holding circuits, in sufficient detail, to diagnose or predict failure scenarios.  The simple diagram I have with my Bounder electrical system would indicate that all internal logic could be eliminated as a failure source simply by switching the time delay OFF.  This time delay disable switch is standard on all switches that I am familiar with.

Transfer switches embedded in some Converter/Inverters may be hybrids.    I'm not at all familiar with their implementation.
 
With the new Phaeton, spent the first 2 weeks on 50 amp shore power. Arrived at a race, started the generator, turned on the air cond., nothing, sure enough, breaker on genset tripped, re-set it, every on - off cycle since then with no problems, my guess.... some anomoly. All is good.   Mark
 
Rutherford,
Have you tried it with the microwave as the load instead of the a/c? I wouldn't assume anything at this point.

Both the generator and the shore power come together at the transfer switch. Everything after the transfer switch is the same. Ergo the problem is at the transfer switch or the generator itself or the wiring in between.

By the way, does the coach have a 30A or 50A shore power?  And if it has two a/cs, do both do the same or is it only one of them?
 
Lou Schneider said:
Some transfer switches use a non-latching relay that's energized when the generator is running.   If the generator voltage drops due to the starting surge of the air conditioner, the relay can drop out and revert to the shore power position.
Click to expand...

If this were he case then soon as the excess load drops off (the switch reverts to shore power) the generator voltage would recover, then 30 seconds later the relay would re-engage and the cycle would start again, within a few minutes the arcing as the relay breaks would weld the contacts together and the ATS would be TOAST. (Stuck in Generator position for life)

So, I don't think this is the problem
 
I agree Romer, "Stuck in Generator" (Or in Shore) mode is common

What is bad is a thread elsewhere I think you have seen the O/P posted his shore cord was hot when using generator

At least one brand of ATS uses too sets of relays Shore and Generator, and control circuits that power up one set or the other after a proper pause

Problem is if the shore power relays weld shut (Get stuck) then when you bring the genny on line you have a hot shore cord

Mine is a single (Well 3) Double throw relays (2 hots and a neutral) so no way can it back feed the mains
 
Just to answer a few of the questions:

The breaker is not tripping on the genset. All I have to do is turn off the A/C, hit the battery disconnect switch off|on and I can repeat this problem all day long without leaving the confines of the motorhome.

I did not attempt to try this with the microwave, however the fact that the A/C ran on shorepower for over 40+ hours along with the fridge, tv and a computer power supply plugged in tells me that the shorepower route and the A/C unit are okay.

The genset is a Generac 6500 unit - that's about my limit there.

We currently have just the one A/C unit but are getting ready to add a second. The current shorepower supply is 30 amp today, but we just finished a 400 amp service upgrade at home and are putting in a full 50 amp power box for the motorhome.

My normal dealer did not have anyone that could even troubleshoot the problem and referred us to another service outfit that specializes in RV generator issues. They started looking at it when I arrived, have had it two days and there has been no word yet on a solution.

 
John From Detroit said:
At least one brand of ATS uses too sets of relays Shore and Generator, and control circuits that power up one set or the other after a proper pause.  Problem is if the shore power relays weld shut (Get stuck) then when you bring the genny on line you have a hot shore cord.
Click to expand...

John,
Can you show us a reference or link to this transfer switch?
Can you show or tell us how you know such an animal exists?
In what RV have you seen this switch used?

Dual relays would add cost, so it can't be a cost cutting idea.  No manufacturer would spend money  to make his switch more  failure prone.  I'm having a problem figuring out why such a thing would exist.
 
Just heard back from the outfit that has been working on the RV. Looks like the voltage regulator on the genset went south and was causing an "overcharge condition". I am going to ask a couple of questions when I pick it up this afternoon, but the charge for the parts and repair was $259 which to me sounds reasonable for the amount of troubleshooting time involved.

I don't understand why smaller loads on the 120v circuit operated okay if this regulator was not functioning correctly. I would think that they too would have been failing, not just the larger load of the A/C causing a complete failure. I am pretty good with electrical issues, but I am still baffled by this one.
 
Small loads tend to be resistive and not very sensitive to voltage or frequency, at least within reason. Moptors and compressors, on the other hand, are quite sensitive. So are electronics like microwaves.

Your generator also sees increased engine load as power demand goes up. There is a engine speed governor as part of voltage regulator function that is supposed to keep everything in sync, since output voltage and frequency depends on maintaining the proper RPMs. Maybe it got increasingly far off as the load went up.
 
Right. The voltage regulator was all over the place, sometimes within range and at other times way off.

I am still puzzled by how it happened. We made the trip down to NC with zero problems, so between hooking up to shorepower, disconnecting and going back to the genset is when it must have occurred. I didn't do anything out of the normal that I can think of and of course I am wondering about this as I would like to prevent it from happening again in the future. I do not normally hit the battery disconnect when switching power, but I am wondering now if I should do so? My background in computers and minor electronics tells be that the normal culprit in the quick death of an electronic component is ESD. But, other than a 4x4 connection box where the power plugs in, there's nothing to ground yourself too and even that box is not a good grounding point due to the tires. Any thoughts or suggestions?
 
The battery disconnect is for 12v loads - I don't see how that could help with a generator component failure. Hard to say what may have caused a voltage regulator failure, though.

The most common cause of generator internal problems is moisture (condensation) accumulating in the windings or electronics. Frequent exercise under load is the best way to keep it dried out.
 
Had an interesting thing happen today and this harks back to much earlier in this thread where we discussed  the need for 12v to keep a gas genset running.  Well, today my wife accidentally hit the house battery disconnect switch adjacent to her seat and guess what? My DIESEL genset stopped running! Guess it takes more than fuel & air to keep the diesel powered generator running too. I wonder why they are designed like that???
 
Without 12VDC to power the blue light in the switch you wouldn't know if the generator was running or not ::)
 
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