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Author Topic: AC Power/GFI Mystery  (Read 597 times)

Rick Daniels

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AC Power/GFI Mystery
« on: April 15, 2018, 04:06:42 PM »
Lost power to outlets in coach so researched forum for guidance.  Went to GFI outlet in storage bay to reset, no luck. Checked for power to outlet to eliminate problems upstream.   Here is the mystery.  There are three 12/2 wires coming into the the outlet box and connected to the GFI.  I assumed that one was "line" and the other two were "load".  Two of the black wires were connected to the "load" side of the the GFI as were two of the white wires.  One of the black wires and one white wire were connected to the line side of the GFI.  Looked normal compared to electric AC distribution schematic I obtained from the forum though not specific to my year model.  When checking voltage between the black wire  connected to the "line" side of the GFI and the white wire coming from the same 12/2 wire I found no voltage but when checking voltage from that same black wire to other white wires from the other two 12/2 wires I found 120 VAC.  I thought i had a fair understanding of 120 VAC but now I doubt myself.  Shouldn't the the  12/2 wire with the hot black wire show 120VAC when checked with the white wire in the same 12/2 wire?  Is the 120 VAC wiring in a motorhome different than a stick built house after the inverter and adjacent breaker box?  Hope my scenario is presented in such a way that can be understood.  I just read it and I am confused.
1999 Beaver Marquis Jasper 40' Cat C-12
2015 Chev 2500 HD
Three Forks, Montana
"Where the Missouri River Begins"

Fred Brooks

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Re: AC Power/GFI Mystery
« Reply #1 on: April 15, 2018, 04:41:16 PM »
Hi Rick, The GFI recepts are on the Inverter circuit, Check the sub-panel box mounted to the roof of the passenger compartments or the inverter itself.
  Hope this helps, Fred Brooks
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6

Rick Daniels

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Re: AC Power/GFI Mystery
« Reply #2 on: April 16, 2018, 02:25:48 PM »
Thanks Fred.  I will start in that breaker box aft of the inverter.  But, shouldn't the line in from that breaker box into the bay GFI have voltage between the black and white wires in the 12/2 wire coming from the breaker box and be connected to the line side of the bay GFI?  Also, the diagram I have shows that the Lavy GFI is fed by the bay GFI.  According to the training I received at  Tijuana Tech (that cost me 4 pesos payable to the bar maid) the second GFI should be fed from the line side of the Bay GFI, not the load side.  Does that sound right to you?
1999 Beaver Marquis Jasper 40' Cat C-12
2015 Chev 2500 HD
Three Forks, Montana
"Where the Missouri River Begins"

Lee Welbanks

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Re: AC Power/GFI Mystery
« Reply #3 on: April 16, 2018, 03:36:11 PM »
Thanks Fred.  I will start in that breaker box aft of the inverter.  But, shouldn't the line in from that breaker box into the bay GFI have voltage between the black and white wires in the 12/2 wire coming from the breaker box and be connected to the line side of the bay GFI?  Also, the diagram I have shows that the Lavy GFI is fed by the bay GFI.  According to the training I received at  Tijuana Tech (that cost me 4 pesos payable to the bar maid) the second GFI should be fed from the line side of the Bay GFI, not the load side.  Does that sound right to you?

Rick, With that GFI from the breaker did you get voltage black to ground? I have seen open neutrals or not connected properly. And Tj Tech is correct the second GFI should be fed on the line side.
Lee, Judy  & Pepper
06 Beaver Patriot Thunder
Wilmington IV 40
525 Cat, 4K Allison
2013 Honda CRV

Paulhowell

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Re: AC Power/GFI Mystery
« Reply #4 on: April 18, 2018, 03:53:02 AM »
Faulty GFCI’s do strange things. Before you go to extreme measures, I would bypass the GFCI and see if you get normal readings on the outlets in the coach.