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popping transfer switch

June 15, 2020, 01:05:37 pm

Hello Foretravelers,'
I am wondering if anyone might be so kind as to point out where I may start diagnosing a popping sound when I'm plugged in to shore power. I found a couple of posts on our trusty Foretravel Tech Talk forum that indicate the sound might be the transfer switch engaging and disengaging.

Here is a summary of observations and post sequence of events:
1) We were out on our first hot weekend when my generator stopped running and default light came on... 
2) We reset the default light by switching the generator off and on from its panel out front, but it wouldn't start until we actually started the coach engine. We ran it for a few hours, and then it started up without the engine. 
3) I took the RV back to storage and noticed the the intermittent popping sound every 30s or so when plugged into the 120v shore power.
4) House batteries were dead a couple of weeks later...
5) Had to run the coach again to get the generator started. Inverter/charger panel had to be reset. Still hearing popping noise.

Question:
Any idea of what more info I might need to start diagnosing/solving this issue based on these observations? I believe we have the original Xantrex ProSine 2.5 inverter/charger on board.

Thanks,
Mike

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Re: popping transfer switch

Reply #1 – June 15, 2020, 01:10:15 pm

With shore power disconnected, generator off and inverter off:

Remove the lid to the ATS.  Any sign of overheating?  Tighten the lugs. With lid off so you can observe, have someone plug in shore power and later start the generator while looking/listening at the ATS.

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Re: popping transfer switch

Reply #2 – June 16, 2020, 09:49:55 am

Thanks Brett,
Went back over last night to check for overheating and tighten lugs as you suggested. I pulled off the lid and saw no signs of overheating. The coach batteries were low again even though I had both "battery" switches off (#1 by the steps and #2 in the basement compartment for the joey bed near the batteries).

I plugged into shore with both still off and no popping. I turned #1 on and the shore contactor engaged and remained sealed in. Inside the coach, the controller panel automatically turned on both inverter and charger and battery status showed 13.75 v.

So, I proceed to turn on #2... When I turned on #2, the contactor would not remain engaged, and the panel showed warning and fault lights. I turned it back off, and #1 would no longer stay engaged even when I reset the panel. This made we aware that I don't know exactly to what and how the #2 battery switch is wired. I do know that with #1 off the coach electricity is off. However, I can still run the electrical cord reel with both in off position.

The generator would not start unless I started the coach. I could not time it right to observe the contactors but assumed the one for the generator engaged as all looked good at the panel. I let it run a while to recharge the batteries.

At this point, I'm not sure I have enough knowledge to proceed further troubleshooting for this. But I certainly appreciate the learning aspect to understand the coach a little better.

Best,
Michael

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Re: popping transfer switch

Reply #3 – June 16, 2020, 10:47:36 am

Agree, you need someone familiar with RV 120 VAC wiring to troubleshoot this.

When you plugged into shore power all was OK.

When you turned on the "salesman switch" by the door to provide 12 VDC from the house battery to house circuits all OK.  This means that the inverter/charger was OK and not causing an issue.

If your coach has OE wiring, the chassis battery is NOT connected/charged by the inverter charger so indeed it is puzzling that connecting this 12 VDC battery causes the 120 VAC ATS to chatter.

About the only thing I would suggest you do is confirm that the 50 amp outlet is properly wired, that your shore power cord ends are clean and not discolored/overheated and that voltage remains above 110 VAC when the "drop out" occurs.

Wiring for 50 amp outlet:

Two outer straights are HOT
Center straight is NEUTRAL
Center round is GROUND

So, either outer to either center= 120 VAC
Center round to center straight= 0
Outer straight to outer straight= 240 VAC

Proper voltage max range= 108-128 VAC (120 +/- 10%)

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Re: popping transfer switch

Reply #4 – June 17, 2020, 06:58:10 am

Ok, thanks again Brett.
Good point. I'm actually plugging into a 120V outlet at the storage that looks like it's daisy chained in series with a bunch of other RVs. This could very well be the problem. I'll check the connectivity and voltage at the source.

Also, I should have mentioned that there is another battery switch #3 in back on the drivers side that I use to disconnect the chassis battery. I hadn't tinkered with that one for this purpose.
Mike

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Re: popping transfer switch

Reply #5 – June 17, 2020, 09:40:47 am

Yes, you could have a poster child for LOW VOLTAGE.  Do not run anything on that unless you want to replace it.

The exception MAY BE the inverter/charger, as they sometimes have a wider than 108-128 VAC range.  Look it up in your inverter/charger owners manual.

And, with either 15 amp (regular house outlet) with adapters to 30 and 30-50, the single hot in the 15 amp is tied to both hots in the 50 amp (in the 30 amp male to 50 amp female adapter).

But you can check voltage at any outlet in the coach to give an accurate picture of voltage.

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