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Thread: motorhome: adding an additional circuit

  1. #1
    Join Date
    Sep 2002

    Default motorhome: adding an additional circuit

    I need to add an additional circuit to the motorhome for the purpose of running additional electric heaters this winter. I have an additional 50A outlet available to me from the RV park so can use this for power.

    I need 3 outlets for the 3 heaters drawing no more than a total of 2.5KW. Space in the motorhome is limited and I want to avoid impacting the existing wiring or trying to modify the existing circuit breaker housing/storage.

    My thoughts were to make up a 50A plug on 30A wiring protected by a 30A breaker and GFCI outlet. (I can purchase a pre-made cable that is a 50A M to 30A F but as a short adaptor cable, the 30A connection would be exposed to the elements. I don't know if this is necessarily a bad thing). To save on space I was also looking for a combination GFCI Outlet and Breaker if a 30A one is available. I was planning on wiring any ground for this second circuit into the first circuit's ground.

    I have heard that the common configuration for motorhome users is to simply run a 30A extension cord from the park outlet to a powerstrip in the motorhome and either connect appliances/outlets to the strip.

    What would be the recommended installation in this case?



  2. #2


    The heater you are using I am taking to be 120 volts and to be plugged in. The maximum amp rating allowed to serve that type heater is a 20 amp 120 volt branch cirucit. Normally you are not allowe two power sources to one structure. However your main service it the mobile home lot pedistal serving you power owned by our park.

    If you want to do this I am picking up you have three heaters. If you ran a 12 awg heavy usage rubber cord plugged into a 120 volt receptacle on yoru remote park pedistal then you could run two heaters on that one added cord. Then you could run your third heater on you motor home wiring leaving the rest of your motor home wiring to carry your other loads.

    Do not install any wiring rated in excess of 20 amps to these heaters. These heaters are not designed for that heavy ampacity wiring and the heater will melt down and cause a fire before you 30 amp plus breaker on that pedistal would trip due to overload.

    The wiring of the cord and plug and the heater itself is wired too light duty to handle the ampacity of anything in excess of 20 amp wiring protected by a GFI 20 amp single breaker.

    If you have to you could run two 20 amp heavy usage rated rubber cords 12/2wGrnd from your pedistal. Then you would have 40 amps going extra to that motor home as temporary wiring. Temporary wiring would be allowed for a maximum of 90 days only though.

    Sorry be safe not sorry


  3. #3
    Join Date
    Sep 2002



    Thanks for the quick response and info. Looks like I made some very basic mistakes in some of my assumptions.

    You are correct, the heater(s) will be plugged in while using the motorhome and I am in the US on 120v.

    I don't think I can rely on the breaker in the pedistal though for this new 20A circuit. The pedistal services 50A and I will be connecting via a 50A to 30A extension cord.

    If I'm now staying with 20A and two heaters (500W and 1500W) on this circuit what components can I install in the motorhome to provide a 20A breaker, gfci and (for a cleaner installation) a couple of outlets?

    thanks again and couldn't agree with you more on safety!


    BTW the original plan was to run 5 heaters total 2 x 1500W, 1 x500W inside the RV body and 2 x 500W heaters in the basement comparments from 2 circuits!

  4. #4


    Seems like you are spending a lot of money to create heating for year around living.

    I suspect you would be surpised if you went to an RV outlet and priced a built in gas heating unit that is designed for your motor home. Then you could use that heater permenantly and in any park you move to.

    To me it sounds like you need to do some research finding the best heating system to provide for your motor home for the money spent.

    Check it out and see if I may be right you having better options for the approximate same money invested.

    Using a built in unit also would be safer than heaters all over the motor home where someone can lay a flammable coat or something too close to one of these heaters and lose you entire motor home.



  5. #5
    Join Date
    Sep 2002



    There is a method to this madness. The RV comes with 2 furnaces that provide more than enough onboard heat without the need of the additional expense of a new circuit and heaters.

    The RV though is going to be stored and used over winter in an RV park in Colorado near to the ski areas. They can refill propane but it would require me unhooking the RV for a short 100' trip to refil the propane tank every 3-4 days. Frequent, short trips like this wouldn't be good for the truck engine.

    Also the forced air furnace does make a lot of noise which is OK during the day but would just be annoying at night. In addition, they aren't really designed for this kind of frequent use (How many RV's are really used in Winter?). It seems fairly common for Winter users to switch to electric, easier for those who already have 50A wiring.

    A quick test last weekend with overnight temps in the low 20's and just 2400W of Electric Heat had the inside of the RV at a low 42 degrees. With some insulation work I managed to raise the RV to a low of 55 degrees. The additional circuit would supply an additional 1100W of heat to the living area which I believe should be enough to get me to worse-case lows in the 60's.

    Then I need to get 2 x 500W heaters into the basement areas where the holding tanks and water supply reside. These froze last weekend....

    A major reason for the purchase was for winter use, so the additional expense of any new electrical circuit is easily justified - in which case upgrading the breakers/wiring to 50A could also be justified!


  6. #6


    I am taking it that you originally have a 50 amp cord and plug to run the motor home and now want to add a second 50 amps for heat.

    If you are going to do this I would install a second 4 circuit Main lug only panel inside your motor home mounted beside your existing mobile home.

    Then run a second four wire 220 volt 50 amp hard usage mobile home cord from that second panel to your park pedistal.

    Then in the mobile home install four 20 amp single pole breakers in that new heating panel. Then run 12/2wground to each location of your heaters installing a single receptacle for that heater in a separate circuit or two receptacles on a circuit if small heaters totalling 2000 watts of heat maximum per circuit.

    This will give you what you want with plenty of power an fuse down your branch circuits.

    The water piping etc. be careful installing a heater in that area unless you have clearance enough to ensure from fire or install heat tapes that are with thermal protection.

    Hope this helps


  7. #7
    Join Date
    Sep 2002

    Default circuit update


    I thought I would give you an update on this. I finally tracked down a company that provides this kind of equipment.

    Basically, the final configuration is as follows (all parts are UL certified and conform to code).

    A single 50A (from the pedestal) cable splits into 2 cables (30A and 20A). I run 2 x 30A extension cord from these into 2 x 30 to 20A adaptor cables and from there into 2 x 20A circuit breaker receptacles. So essentially I have 2 additional circuits protected by 20A circuit breakers.

    On each of these new circuits I will have one 20A GFCI protected outlet and further along the circuit one double outlet. All this will be on 12 guage Romex.

    I will have one 1500W heater on one circuit and two 500W heaters on the other circuits.

    On the existing main 30A supply I will run one 1500W heater and one 750W heater. This should be enough to keep the RV warm internally and protect the basement compartment pipes/tanks from freezing.

    This is all available from powersolutions (Bill Nemecek) at 1-800-536-4995



  8. #8



    Be careful. The statement said that ALL PARTS are ul listed. It did not say this power solution was UL listed. I suspect if you call or email UL they will confirm that this is in no manner UL approved as an assembled product. Way too much chance of having more than one power source to a structure that the NEC forbids and also of having like hot wires reading zero potential between them thus adding load to the white wires if combined causing a hazardous condition of possible melt down or the motor home being energized when someone unplugged one cord and thought that killed the power to that motor home.

    Only do what I suggested using two hot wires reading 240 volts between the two hot wires and not zero volts between the two hot wires.

    Be careful you are not reading between the lines on that statement. The components by themselves are UL listed but not that assembled conversion product.


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