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GoodCamper's avatar
GoodCamper
Explorer
Jul 05, 2015

An electrical system puzzle

We have a 2012 Keystone Cougar 5th wheel with a 50amp system. This rig is brand new to us, but we have several years of travel trailer experience. The rig has a WFCO power distribution center and a WFCO WF-9800 converter. The distribution panel has a 15A breaker for the GFI 120v outlets and a 15A breaker for the non-GFI 120v outlets. We're plugged into a 20a GFI shore power outlet (at home) through the 50A cable, a 50 - 30A adapter, and a 30 - 15A adapter.

Got a puzzling electrical problem. The 1st clue something was wrong: my wife had the 12v radio/DVD player on. She was vacuuming, connected to a GFI outlet. I flipped the "RECEPT" (non-GFI outlets) breaker on - so we could run the refrigerator - and the volume on the radio dropped significantly! I checked the voltage at one of the non-GFI outlets and it was about 118v. The refrigerator worked. The vacuum cleaner worked when plugged into a non-GFI outlet. That was yesterday morning.

Today, the "Check" light on the refrigerator came on. No 120VAC and it was trying to run on propane, which was shut off. Turned the refer off/on - same problem. Checked and found no 120VAC at any outlet. The breaker in the source 20A GFI shore power outlet had popped. Now, every time I turn on the distribution panel breaker for the non-GFI
outlets in the rig, the GFI breaker on the shore power source outlet pops, even if nothing is plugged into these non-GFI outlets. Powering the GFI outlets in the rig works fine.

Sorry for the LONG story, but I don't know how else to explain it. I'll probably have to take it somewhere for service, but I'm pretty good at DYI and any wisdom or suggestions will be greatly appreciated!

15 Replies

  • Harvey51's avatar
    Harvey51
    Explorer
    Aug 03, 2015
    Thanks, Drew; I got confused after doing some reading and seeing a post about plugging a 50 A RV into a 30 amp outlet!
  • DrewE's avatar
    DrewE
    Explorer III
    Aug 03, 2015
    Harvey51 wrote:
    The standard adapters should connect both 50A hots to the single 30A or 20A hot and neutral to neutral. Given that a upstream GFI should not trip.

    I don't understand this! Isn't there 240 volts from one hot to the other? Surely connecting them together would trip both circuit breakers.

    I would expect the adapter would connect to only one side of the double 50 amp supply. There ought to be a 30 amp breaker in the adapter but it isn't really needed because the RV has one already.

    It would be interesting to understand how an adapter causes a GFI to trip.


    You're thinking of an adapter working in the opposite direction from what's being described. An adapter to plug a 50A plug into a 30A or 20A supply just connects the two hot leads of the 50A plug to the hot lead of the supply. You no longer have 240V between the two hots (they're on the same leg), which is usually of no consequence in an RV since there typically are not any 240V circuits. The total power you can use is, of course, limited by the supply.

    What you're thinking of is an adapter to plug a 30A (or 20A) device into the 50A circuit, and indeed these do only connect to one leg of the 50A split phase service. You're also correct that they should have a fuse or circuit breaker in them for safety, but generally don't. (Usually the makers get around this by putting fine print on the product or packaging that it's only to be used on circuits protected to the lower current rating...presumably knowing full well that this is very rarely what happens in actual use.)
  • MrWizard's avatar
    MrWizard
    Moderator
    Aug 03, 2015
    Are we talking pedestal output
    Or
    RV input
    There is no power on the unplugged RV cord
    The shore pedestal can have 50a, 30a, and 20a receptacles

    There is No short using a 30 female to 50 amp male
    That adapter only uses ONE (1) of the 50 amp hot legs not both

    And a 30a male to 50a female only has ONE hot leg at the pedestal to connect internally, to supply both sides of the 50a RV from one 30 amp leg

    The dual cord adapter with a 30 amp plug and a 20 amp plug
    Can provide 30 amps service to one leg
    And only 20 amp service to the other leg
    But it uses a common neutral inside the RV shore cord
    If an up stream gfi is tripping you have a current leak in the adapter box
  • Harvey51's avatar
    Harvey51
    Explorer
    Aug 03, 2015
    The standard adapters should connect both 50A hots to the single 30A or 20A hot and neutral to neutral. Given that a upstream GFI should not trip.

    I don't understand this! Isn't there 240 volts from one hot to the other? Surely connecting them together would trip both circuit breakers.

    I would expect the adapter would connect to only one side of the double 50 amp supply. There ought to be a 30 amp breaker in the adapter but it isn't really needed because the RV has one already.

    It would be interesting to understand how an adapter causes a GFI to trip.
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Jul 26, 2015
    ktmrfs wrote:
    depending on the dogbone your using to go from 240V 50A to 120V you could end up with a GFI that trips. A 50A service is two legs of 120V. And depending on how you go from the 50A/240 to 120 you could either end up with only one leg powered or the two legs tied together. and how it ends up getting configured can be incompatible with a upstream GFI outlet. GFI outlets will trip if they see ground/neutral bonding downstream or some aspects of a 240 trailer to 120V trailer adapter. In fact some of the 50A/240V to 30a/120 adapters will say NOT compatible with GFI outlets.
    The standard adapters should connect both 50A hots to the single 30A or 20A hot and neutral to neutral. Given that a upstream GFI should not trip.

    Even if some non standard adapter connects to only one hot the upstream GFI should still see balanced hot and neutral current. And most users would be less than thrilled with AC power in half of the rig and would soon find a standard RV adapter.

    Plugging a RV into a GFCI circuit and trying different appliances is a good method of checking for a ground fault.

    The only adapter that I'm aware of that will trip a upstream GFCI is the cheater cord and probably shouldn't be used even with non GFCI plugs.
  • GoodCamper's avatar
    GoodCamper
    Explorer
    Jul 25, 2015
    I really appreciate all the help and advice you guys have offered! Just goes to show, RVers are the greatest people!

    I installed an outdoor 30 amp box to plug the Cougar into and since then, we've experienced no problems with the electrical system. I think maybe ktmrfs hit this one on the head regarding the adapters (50a to 30a to 15a) not playing nicely with GFI outlets.

    Thanks again to all of you!

    -- Pete
  • GoodCamper's avatar
    GoodCamper
    Explorer
    Jul 06, 2015
    Thanks, everyone, for your help! I'll check out as many of your suggestions as I can and let you know what happens.

    --Pete
  • neilnbe's avatar
    neilnbe
    Explorer
    Jul 06, 2015
    You have either a neutral crossed with one of the circuits your using or you have a bad neutral connection somewhere. The neutral can show as good with a Tester then actually break connection when under load. Start with the 2 120v circuits in question and go from there. You'll have to check upstream and downstream receptacles as well on both circuits.
  • YC_1's avatar
    YC_1
    Nomad
    Jul 06, 2015
    Batteries are likely low due to symptoms you mentioned. Once they got too low the charger may have gone into a large charge mode and have overloaded the breaker you speak of. Check your batteries closely and measure the voltage across them.

    IF your onboard charger/converter has an actual AC plug, run an extension cord to it and run it by itself assuming your battery voltage is indeed low.

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