Automatic Transfer Switch testing

[ajg617]

I have a 15amp circuit feeding the RV via dogbone during the winter to keep the batteries charged when the battery heaters are going and the solar panel is covered in snow. This time I fired off my generator for a monthly run and didn’t unplug the 50amp connection first - normally only run the genset when there is no shore power. Popped a GFCI and CB in the house. I was under the impression that the Solitude has an Automatic Transfer Switch (sure looks like one behind the pass thru wall) and that the ATS would prevent back feed by cutting off power to the 50Amp connector in favor of the generator automatically. That didn’t seem to happen. Factory Onan and cabling (except for the LiFePO4s).

From what I can read (nothing in the manual), there doesn’t appear to be any Warnings about disconnecting shore power before running the generator and the ATS should automatically adjust? Haven't had any spurious wiring or electrical problems at all. Just that this one surprised me - didn't expect any flow back into the house.
Thanks,
John

[TedS]

May be mis-wired and the generator is not the default/preferred connection?

[ncitro]

ajg617 Most of my ATS experience comes from motorhomes, but its a bad idea to switch them under load. The contacts in the relay will arc over as they switch from one source to another, and eventually will weld themselves into place and not switch anymore. That said, it should be pretty difficult for the ATS to cause what you saw, that would mean its somehow shorting the two inputs as well as the output. The first thing I would do if you have a meter and are comfortable working with electricity is unplug the rig, fire up the generator, and see if you have voltage at the power inlet to the RV. There should not be any, and if there is there is some kind of wiring issue. If there is not, then possibly a transient on the ground caused the GFCI and breaker in the house to trip. You would need a scope to see whats going on with that.

[TedS]

This article by Mike Sokol may help.
https://www.rvtravel.com/rvelectrici...-switches-101/

[TedS]

ajg617 Most of my ATS experience comes from motorhomes, but its a bad idea to switch them under load. The contacts in the relay will arc over as they switch from one source to another, and eventually will weld themselves into place and not switch anymore. That said, it should be pretty difficult for the ATS to cause what you saw, that would mean its somehow shorting the two inputs as well as the output. The first thing I would do if you have a meter and are comfortable working with electricity is unplug the rig, fire up the generator, and see if you have voltage at the power inlet to the RV. There should not be any, and if there is there is some kind of wiring issue. If there is not, then possibly a transient on the ground caused the GFCI and breaker in the house to trip. You would need a scope to see whats going on with that.

The switching mode is break-before-make so that all sources are not connected to load when the switch occurs. Yes there is arcing as the source is disconnected from the load.

[ncitro]

The switching mode is break-before-make so that all sources are not connected to load when the switch occurs. Yes there is arcing as the source is disconnected from the load.

Yes thats right, thats why it should be impossible for the generator to backfeed the power inlet. I suspect a transient tripped the breaker, but best to check the inlet on the rig to make sure there is not something else going on.

[Scott'n'Wendy]

but its a bad idea to switch them under load. The contacts in the relay will arc over as they switch from one source to another, and eventually will weld themselves into place and not switch anymore.

While what you say is true, it was just a 15a cct which will never draw much of an arc.

[ncitro]

While what you say is true, it was just a 15a cct which will never draw much of an arc.

Yes the arc should not have been enough to cause an issue with the transfer switch, that was just advice to not let it switch under load.

[ajg617]

If I understand correctly with Genset on and stabilized (I usually hear the click and 120V comes on), there should be nothing hot at the 50amp connector. If there is, I probably have an ATS that isn't doing its job correctly. I don't think I've ever kicked the genset on with shore power connected.

[Scott'n'Wendy]

If I understand correctly with Genset on and stabilized (I usually hear the click and 120V comes on), there should be nothing hot at the 50amp connector. If there is, I probably have an ATS that isn't doing its job correctly. I don't think I've ever kicked the genset on with shore power connected.

I would do an audit of your wiring and thoroughly understand the operation of your ATS - read up on the manual. Then make sure you have correct wiring and the relay is not faulty.

[ncitro]

If I understand correctly with Genset on and stabilized (I usually hear the click and 120V comes on), there should be nothing hot at the 50amp connector. If there is, I probably have an ATS that isn't doing its job correctly. I don't think I've ever kicked the genset on with shore power connected.

That’s correct. If everything is working as it should you should not read any voltage between any of the pins at the power inlet on the side of the trailer when the generator is running.

[ajg617]

I would do an audit of your wiring and thoroughly understand the operation of your ATS - read up on the manual. Then make sure you have correct wiring and the relay is not faulty.

Never received any manual - just went out an looked at it - WFCO WF-T57-R. Pretty clear label that says 20-60 seconds after starting generator, load will transfer from shore to genset. Measured voltage on the 50Amp plug pins - two read 5V and one read 7V. Suspect I have a leak somewhere.

[Scott'n'Wendy]

- two read 5V and one read 7V. Suspect I have a leak somewhere.

Reference is really important. Need to make sure the neutral reference is solid...
This is why I was saying an audit (thorough check of the wiring) is needed.

[acoleman43]

I have a 15amp circuit feeding the RV via dogbone during the winter to keep the batteries charged when the battery heaters are going and the solar panel is covered in snow. This time I fired off my generator for a monthly run and didn’t unplug the 50amp connection first - normally only run the genset when there is no shore power. Popped a GFCI and CB in the house. I was under the impression that the Solitude has an Automatic Transfer Switch (sure looks like one behind the pass thru wall) and that the ATS would prevent back feed by cutting off power to the 50Amp connector in favor of the generator automatically. That didn’t seem to happen. Factory Onan and cabling (except for the LiFePO4s).

From what I can read (nothing in the manual), there doesn’t appear to be any Warnings about disconnecting shore power before running the generator and the ATS should automatically adjust? Haven't had any spurious wiring or electrical problems at all. Just that this one surprised me - didn't expect any flow back into the house.
Thanks,
John

Your shore power wiring and generator wiring may be sharing a neutral. I would look over the wiring into the ATS to make sure the shore circuit and generator circuit are wired correctly (completely separate).

[Scott'n'Wendy]

Your shore power wiring and generator wiring may be sharing a neutral. I would look over the wiring into the ATS to make sure the shore circuit and generator circuit are wired correctly (completely separate).

I don't have an ATS, but would I be correct thinking it is a 3 pole contactor switching two hot legs and the neutral?