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Topic: Shore power issue (Read 705 times) previous topic - next topic

Shore power issue

Got a strange one that I just cant figure out. 95 u320. Good price, looks great, but anytime plugged i to power at a campsite pops breakers. Owner said he just runs gen, bit I plan to plug in. I know just enough to be trouble. With a multimeter spliced into the grounded outlet in his driveway, I measured 12-30 volts (open circuit) and 5-8 milliamps on the ground pin of the 50 to 30 to 15 amp adapter we used for testing. Tried turning different breakers on and off. Tried different loads. This rv always seems to send power thru the ground pin which blows GFCI breakers.  Any ideas? The transfer switch maybe? I dont really know how to approach this issue. But I dont want to skip a good deal on a Foretravel if its an easy fix.
95 U300SE

Re: Shore power issue

Reply #1 –
Just as a general rule, if you are starting out with an entirely unknown system, start at the electrical receptacle. Is it wired correctly and voltages(s) correct? Is ground bonded to neutral? Once you have determined all are correct, plug in 1st adapter and check same. Repeat until you get to the plug for the coach. Once you know all is well with your cords, adapters, and wiring, you can start looking for problems with the coach. I would start looking for neutral-ground bonding and a short to ground on one leg or power.

TOM
SOB (Some Other Brand) division
1995 Wanderlodge WB40
8V92 :D

Re: Shore power issue

Reply #2 –
Quote from: rvlooker –
  The transfer switch maybe? I dont really know how to approach this issue. But I dont want to skip a good deal on a Foretravel if its an easy fix.
This is not good, to say the least. Why the PO did not address the problem and "just ran the gen set" has cheapskate written all over it. Do you know what a "coach buck" is? You could spend some trying to figure this out. Have you checked the male & female shore connections at the coach? The coach could have taken a "pedestal hit" and fried some of the connections. We took one such hit and it not only fried the connections, but crawled into the transfer switch and smoked it, as well. In our experience, we had NO POWER from either shore or gen, so your experience is a little different. To replace the connections on the cord, the female connection at the coach, the transfer switch, was a CB and some serious change. It could be simple, but get your pocket full. Let us know what you find.
UPDATE: Does the coach have "that smell" anywhere?
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
Previous: 1983 Airstream 310 turbo diesel, 1979 Airstream 280 turbo diesel
                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: Shore power issue

Reply #3 –
Quote from: rvlooker –
Got a strange one that I just cant figure out. 95 u320. Good price, looks great, but anytime plugged i to power at a campsite pops breakers. Owner said he just runs gen, bit I plan to plug in. I know just enough to be trouble. With a multimeter spliced into the grounded outlet in his driveway, I measured 12-30 volts (open circuit) and 5-8 milliamps on the ground pin of the 50 to 30 to 15 amp adapter we used for testing. Tried turning different breakers on and off. Tried different loads. This rv always seems to send power thru the ground pin which blows GFCI breakers.  Any ideas? The transfer switch maybe? I dont really know how to approach this issue. But I dont want to skip a good deal on a Foretravel if its an easy fix.
I disconnect the transfer switch for generator and see what would happen. if that fixed it check generator out  and replace switch

Re: Shore power issue

Reply #4 –
Were you reading the voltage coming from the coach reading the 12-30 volts on the power cord without the generator running? If so where is that voltage coming form? Inverter? Is it only tripping ground faults at the power pedestals? Did you turn off all circuit breakers at the same time when getting the voltage?
Post answers and I might be of help
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Shore power issue

Reply #5 –
The only place it has any smell is slight leaks in the bedroom cabinets and some front clearance light leaks. The price is right and leaves many coach bucks for repairs later on if i do buy.

All electrical troubleshooting was done plugged into a house outlet with the ground wire disconnected. Never ran the genset. With everything off there was nothing on ground, but anything at all that was turned on created a reading on the multimeter that was wired into ground. The breaker labeled powerwatch and vacuum had a big impact. It is very weird. No one thing causes this issue. Which is why I was thinking its something in the ats or breaker box. I took apart the twistlock recepticle and all wires looked good and tight connections.
95 U300SE

Re: Shore power issue

Reply #6 –
If you are going to trouble shoot and fix this yourself it doesn't appear to be a big money issue just your labor. I personally would not let the issue stop me from buying if the price is right. An ohm meter will find it eventually.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Shore power issue

Reply #7 –
By "that smell", I meant burned wiring. Take a whiff of the transfer box; in ours, it's in the engine comp on the right from above.
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
Previous: 1983 Airstream 310 turbo diesel, 1979 Airstream 280 turbo diesel
                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: Shore power issue

Reply #8 –
Have you tried plugging it in with all the circuit breakers at the foot of the bed switched off?

Have you tried it on a non gfi protected circuit?
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Shore power issue

Reply #9 –
Sounds like the neutral conductor and grounding conductor are tied together somewhere. Grounding conductor is for fault current only. Unlikely a fault condition if it happens with any one of the breakers turned on. Check for any accidental or intended connections between these two conductors.
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: Shore power issue

Reply #10 –
We really don't know enough to help.

Absolutely, first thing is to certify that the house outlet IS properly wired.

That means long straight= neutral, short straight= hot and round= ground. We are assuming this is a regular house-type 15 amp outlet.  If in an older house, most likely it is NOT up to code (no ground).

Has this been confirmed?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Shore power issue

Reply #11 –
Use one of these to test the house and coach, should be in every coach toolbox.
Note that most older coaches when using a power cord adapter and then plugged into a 120V GFCI outlet will trip the GFCI due to small insulation leakages in the older appliances and wiring. The GFCI outlets within the coach work as intended, they are monitoring just the leakage current of what is directly plugged into them.

Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Shore power issue

Reply #12 –
What breakers trip?  Why are you plugging into a GFCI outlet?  Does everything work ok on a non-GFCI outlet, like a 50-amp 220 pedistal?

Re: Shore power issue

Reply #13 –
Thanks for the replies! The testing I did was plugged into a 15 amp, non GFI outlet in the commercial building where he keeps it parked, which is a brand new construction finished last year. It isnt rented or built out, and he stores his toys inside.

 For testing I cut into an extension cord, cut the ground wire and put my multimeter inline with the ground. I did not test the building wiring to be sure it is correct, but he told me this was an ongoing issue whenever he tried to plug into pedestals with ground fault protection. He attempted to have a few shops fix it, but nobody ever got to the bottom of it. Google tells me most GFIs trip at 4-5 milliamps, and I am seeing that and more. I tried to eliminate everything but no matter what circuit is powered on, i always saw some current flowing across ground. I was really disappointed it wasnt one thing, like the charger or fridge, but i dont really understand whats going on or what to do next. everythibg works ok on a non gfi 15 amp, and I assume would be fine on any non gfi circuit. But it seems most parks have gfi breakers these days.
95 U300SE

Re: Shore power issue

Reply #14 –
No, only 15 and 20 amp shore power are normally GFI protected.

30 and 50 are not.

But, if it trips a GFI with the coach's main breaker (the pinned dual 50's) off, then look for a problem in the shore power cord, connection to coach or ATS.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Shore power issue

Reply #15 –
Do you have a reel?  The carbon brushes can and do go out.
1988  40' Grand Villa Cat 3208t

Re: Shore power issue

Reply #16 –
No reel, and no, there is no power thru ground unless some load is on (even the powerwatch creates a ground current)

There is a marinco round twist lock recepticle in the sewer connection bay. We tested with a big yellow 50 amp cordset and a 50-30, then 30-15 adapter. Not ideal but it demonstrated a fault. I will enlist more help from friends who are smarter than me in troubleshooting this. Was hoping someone here has had a similar issue in the past, but maybe this is a special case.
95 U300SE

Re: Shore power issue

Reply #17 –
Disconnect the shore power cord and put an ohmmeter between the neutral bus and grounding bus (or chassis ground) and see if you have continuity.
If so this explains the current present on the ground conductor in the shore power cord as it is a parrallel path. You are correct that it only takes about 5 milliamperes unbalanced current on the line and neutral to trip a GFCI.
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota
 

Re: Shore power issue

Reply #18 –
That was my next step, even going to borrow a meggar meter (and try to co vince the owner of said meter to join me in troubleshooting)

Will report on results next week. Probably going to buy this if I can track this down!
95 U300SE