Why did I fry the GFCI? Electrical puzzle

Bentspoon · 05-12-2018, 02:47 PM

I am perplexed at this latest occurrence. I am pretty good with electrical so I am hoping the local expertise can help me figure this out.

When I got our Forest River Class C, we planned to boondock on occasion. My SO uses a sleep apnea machine so I had to upgrade the battery and install an inverter since the rig did not have one. Electrically, I hooked it across the battery. It simply was not practicle to install a transfer system. I would be the transfer system by plugging my power cord into either the shore power, the generator or the inverter. Of course, I had to be careful to switch off the converter if I wanted to use the inverter.
Of course the first time I boondocked I got carried away and applied inverter power with the converter on. It fried the GFCI on the inverter. Once the issue was corrected, the GFCI would not reset so it had to be replaced. OK – lesson learned – label applied. I knew I wasn’t supposed to do that anyway.
This time, I was on shore power. The inverter was off and no load (nothing plugged in). I casually turned the inverter on to meter the battery. There was a loud buzzing and the GFCI was, once again, fried but the inverter itself was metering the battery as expected. Once I unplugged shore power and then turned on the inverter, it metered the battery as expected but the GFCI would not recover. It just killed the GFCI - there was nothing plugged into it!!
WTF! Ground loop??

Duckogram · 05-12-2018, 04:51 PM

First thought: Too much amperage.

Bentspoon · 05-12-2018, 05:25 PM

Duckogram, there is nothing plugged into the inverter. It is simply connected to the battery. It shouldn't draw any current except that which it uses to function. That current would not be seen by the output GFCI. Theoretically, no current came through the GFCI.

llr · 05-12-2018, 09:12 PM

Are you sure it's a cfci? Can you post a picture?
Leaving the converter on should not hurt anything except drain the battery faster as it trying to charge the battery but with bosses it will always drawer more current then it puts into the battery.

**wmtire** · 05-12-2018, 09:36 PM

Quote:

Originally Posted by Bentspoon

Electrically, I hooked it across the battery. It simply was not practicle to install a transfer system. I would be the transfer system by plugging my power cord into either the shore power, the generator or the inverter. Of course, I had to be careful to switch off the converter if I wanted to use the inverter.

Let me ask about what I have emboldened in red and blue above. Are you stating that you have the "inverter" wired in such a way that you can plug your RV's shore power cord into it directly...thus powering up all the 120 volt AC items from the battery/inverter-which includes the converter if you don't switch it off?

I assume you are saying you are switching the converter off so it doesn't take power from the battery to recharge the battery? Inverter drawing current out of the battery while converter pushing current into the battery?

cavie · 05-12-2018, 09:36 PM

Quote:

Originally Posted by Bentspoon

I am perplexed at this latest occurrence. I am pretty good with electrical so I am hoping the local expertise can help me figure this out.

When I got our Forest River Class C, we planned to boondock on occasion. My SO uses a sleep apnea machine so I had to upgrade the battery and install an inverter since the rig did not have one. Electrically, I hooked it across the battery. It simply was not practicle to install a transfer system. I would be the transfer system by plugging my power cord into either the shore power, the generator or the inverter. Of course, I had to be careful to switch off the converter if I wanted to use the inverter.
Of course the first time I boondocked I got carried away and applied inverter power with the converter on. It fried the GFCI on the inverter. Once the issue was corrected, the GFCI would not reset so it had to be replaced. OK – lesson learned – label applied. I knew I wasn’t supposed to do that anyway.
This time, I was on shore power. The inverter was off and no load (nothing plugged in). I casually turned the inverter on to meter the battery. There was a loud buzzing and the GFCI was, once again, fried but the inverter itself was metering the battery as expected. Once I unplugged shore power and then turned on the inverter, it metered the battery as expected but the GFCI would not recover. It just killed the GFCI - there was nothing plugged into it!!
WTF! Ground loop??

I am an electrician and cannot understand a thing you have stated here. I will say one thing then I'm gonna set back and just follow the thread. 2 gfi's don't play nice together. The shore power has one and your coach has one and the generator has one. One of them is gonna trip and it will not reset until one of them is removed from the circuit.

Bentspoon · 05-12-2018, 11:36 PM

The inverter I am using has a battery meter and a GFCI receptacle for AC out. It's a Xantrex.
I have a 30 amp AC cable for my input on the rig. I either plug that into a) shore power, b) on board generator power or c) my installed inverter. In the case of scenario c, I have to disable the Converter.
In the scenario I am asking about I have that power cable on shore power. The converter is on. Then I turned on the Inverter to read the inverter's meter. Now there is no AC load on the GFCI output - Nada - the inverter powers NOTHING. I was just using it as a meter because it was convenient and its GFCI receptacle, which had nothing plugged in - no load at all, fried!!! By the way the Xantrex is fine but the GFCI will not reset.
I don't need to know the answer. I just won't do that again. But I like explanations - I want to know.
Thanks for playing
Bentspoon

Bentspoon · 05-13-2018, 12:09 AM

This was stated in a post "Leaving the converter on should not hurt anything except drain the battery faster as it trying to charge the battery but with bosses it will always drawer more current then it puts into the battery."

This is false. If the inverter and converter are in a loop, there is a positive feedback condition which is going to cause a run-away condition and fry things by drawing much current. It happens quick. I know. I did it.

By the way, I did not use a transfer switch because of space and proximity of components. It isn't practical and attests to the fact that this little class c was never meant to boondock. This came as a surprise to me and I set out to modify it from the get-go. I thought RV inherently meant boondocking. This was designed for RV resorts only.
Bentspoon

**wmtire** · 05-13-2018, 03:51 AM

Quote:

Originally Posted by Bentspoon

Thanks for playing
Bentspoon

I'll take that as my exit cue from this conversation. Peace Out, Brother.

https://www.urbandictionary.com/defi...0For%20Playing

ScottBrownstein · 05-13-2018, 07:49 AM

Xantrex PSW inverters are particular about which GFI they can support. Did you get a replacement from Xantrex or one that was considered compatible (List attached)?

I have had people plug all sorts of things into my Xantrex. If they draw too much current it simply shuts down and comes back all by itself when the load is removed.

Bentspoon · 05-13-2018, 09:42 AM

Meant with a sense of humor - sorry if I offended

Bentspoon

Oaklevel · 05-13-2018, 10:13 AM

There is more going on here so with out more info no one of us can help.

**wmtire** · 05-13-2018, 10:55 AM

Quote:

Originally Posted by Bentspoon

Meant with a sense of humor - sorry if I offended

Bentspoon

OK, I may have just took it wrong.

Back as to your why, converters with their switching supplies, refrigerators, and other things in the RV have some current leakage. It depends on how much, as to whether or not it trips a GFCI, which trips at as little as 5 milliamps difference between the hot leg and neutral return current.

The way you are plugging directly into the inverters GFCI outlet with your shore power cord, then everything connected in your RV is going thru that one GFCI. Enough leakage on anything in the RV is going to trip the GFCI. This leakage could be an appliance, the converter, a bad/loose wire connection, and a multitude/combination of things

This is part of the same reason why you don't necessarily want to plug into a 15 amp GFCI at your house. Each RV is going to be a little different, and some may trip the GFCI and some may not.

This article may also help:

Power Inverters and GFCI Tripping | Don Rowe Power Inverters Blog

MontyPP · 05-13-2018, 11:25 AM

As a novice why would the gfci trip if there isn't a grounding situation? Maybe you're wired wrong?

Duckogram · 05-13-2018, 11:28 AM

OK, I read the follow-up and still can’t seem to get how a gfci can fry (not just tripped) with no load. So I’ll just follow along hoping to learn something.

fonzie · 05-13-2018, 11:32 AM

Install a regular receptacle instead of GFCI in inverter and see what voltage is, maybe inverter is defective. If all good then install new GFCI that is compatible with inverter output.

Bluepill · 05-13-2018, 11:59 AM

A GFCI outlet is an electronic device with internal solid state and other electronic components. Just like other consumer electronics, they can fail internally and damage themselves. I would not be overly worried by the failure. Just replace it if you intend to plug into it, or disconnect/remove it if not.

If you choose to replace it and it happens again, then it is worth your time to investigate further.

**wmtire** · 05-13-2018, 12:26 PM

Quote:

Originally Posted by MontyPP

As a novice why would the gfci trip if there isn't a grounding situation? Maybe you're wired wrong?

Mike Sokol (our resident electrical guru and fellow member) has several good articles on his website that explain what a GFCI actually does, and how it works. You can find that one here:

RV Electrical Safety: Part VIII â€“ GFCI Theory | No~Shock~Zone

Mike also explains how to test for current leakage, which the OP may want to do, if he can just plug his converter into a regular extension cord.

RV Electrical Safety: Part X â€“ GFCI Testing | No~Shock~Zone

We always recommend Mikes "No Shock Zone" website and book, as it could actually save your life.

D W · 05-14-2018, 10:36 AM

Quote:

Originally Posted by cavie

I am an electrician and cannot understand a thing you have stated here. I will say one thing then I'm gonna set back and just follow the thread. 2 gfi's don't play nice together. The shore power has one and your coach has one and the generator has one. One of them is gonna trip and it will not reset until one of them is removed from the circuit.

X2. I will say one thing also, if you're "frying" GFCI's, you have a serious electrical misconfiguration (load imbalance?). Maybe.

**Bama Rambler** · 05-14-2018, 11:22 AM

When I first read this I interpreted it to say that you replaced the inverter with a new one, but after going back and rereading it, I see that just the gfci was replaced.

Was the gfci part of the inverter from the factory?
Did you replace the original one with an identical model gfci?

If it was part of the inverter from the factory, then I suspect a problem with either the inverter or the wiring between the inverter and gfci.

You may also like: