50-30 adaptor

Question

Hi GuysThis is for the electrical wiz peopleI have a 50 amp service on my 5th wheel.I just installed a slide out tray in the frontCompartment rated for 250lbs. I put my Yamaha 3000ise on it. Works great. IInstalled a plug outlet in the front using some L5 30 amp twist lock connectors I hadAt home. I made a short 5ft length cord with The L5 twist lock plug on the end that plugs Into the generator and plug the other end Into the outlet I installed in the front. MakingSense so far?  On The cord going to the outlet I ran thisTo my distribution panel. Now a 50amp can use a 30 adaptor , thatAdaptor connects Both hot legs togetherSo both sides of the RV circuit gets power.I understand that. The 50 amp plug has 4 contacts30 amp plug has 3. My install works BUT onlyPowers Some of the RV circuits. IF I plug the 50-30 Amp shore power adaptor Only into the trailer everything worksBecause the adaptor connects both legs together.That's all fine but I have the 50-30 amp adaptor hanging outOf the back shore power outlet.So now finallyComes the Question. If I connect Both legs togetherAt the distribution panel that is actually 2 breakersIt's more or less the same as the adaptor plug so IWouldn't need to use it... I have only ever seen30 amp service in Alberta and don't even carry the50 amp super heavy stiff cord in the RV... But withBoth legs of the 50 amp service connected at the Distribution panel would it work IF it was pluggedInto a 50 amp outlet.ThanksDale  M

drewe · Answer

NO!!!  Do not even think of doing that.If you short the two legs together, you make a short circuit when plugging into a normal 50A outlet.  The two legs have opposite phasing, so they have 240V RMS between them.It sounds to me as though you're backfeeding your panel from the "outlet" for the generator.  This is a dangerous and (in most cases, at least) illegal way of doing things.  You need some manner of transfer switch that does not let you connect the generator and the shore power cord at the same time.  As it's wired now, if I'm understanding your post correctly, you have 120V exposed at the 50A plug when running off the generator (at the least), and if you connect to shore power with the generator plugged in you stand a very good chance of destroying the generator (and hopefully not doing anything worse).  If you were to plug in a traditional, non-inverter generator, you could very well destroy it in extremely violent fashion, with heavy parts of the generator's alternator flying free.Please, please, pretty please get help from someone who's qualified to do electrical work.

choochooman74 · Answer

I would never do that.  Now, there is no chance of ever plugging into a 50 amp outlet without a short circuit between the 2 hot legs.

westend · Answer

The best way here would be to wire an adaptor from 50 amp service to 30 amp service and plug that adaptor into the generator's 30 amp twistlock. You would only need a short length of 50 amp cord and that small cord could be used as an extension cord for some situations, combined with your OEM 50 amp cord.

dale__m · Answer

DrewE wrote:NO!!!  Do not even think of doing that.If you short the two legs together, you make a short circuit when plugging into a normal 50A outlet.  The two legs have opposite phasing, so they have 240V RMS between them.It sounds to me as though you're backfeeding your panel from the "outlet" for the generator.  This is a dangerous and (in most cases, at least) illegal way of doing things.  You need some manner of transfer switch that does not let you connect the generator and the shore power cord at the same time.  As it's wired now, if I'm understanding your post correctly, you have 120V exposed at the 50A plug when running off the generator (at the least), and if you connect to shore power with the generator plugged in you stand a very good chance of destroying the generator (and hopefully not doing anything worse).  If you were to plug in a traditional, non-inverter generator, you could very well destroy it in extremely violent fashion, with heavy parts of the generator's alternator flying free.Please, please, pretty please get help from someone who's qualified to do electrical work.Hi.After reading your replies I can see that I am back feeding myMy panel from the generator and yes the prongs would be Hot. I reallyNever noticed the exposed prongs as the whole 30 amp cord was attached attachedAnd coiled up on the ground.But I guess if I would have touched the ends I would have found out in a hurry.Sounds like I need to use the normal 50-30 amp adapter and the shore power cord and just run it from The back of the trailer up to the generator, or get a transfer switch.I was trying to be able use the generator up front without running the main powerCord from the back of the trailer to the front.Thanks GuysDale

wa8yxm · Answer

If you jumper at the distribution panel then if you plug into 50 amps at a campground bad things WILL happen (Very bad, direct short on 240 volts, Major sparks)

Now you said you made up a cord with the Twist Lock on one end, and an Outlet on the other., I assume this is a 50 amp outlet on the other end.. YES?NO? If YES read on
The 50 amp outlet has 4 wires/screws/contacts

One screw is Green, or marked "G", the assoicated pin is kind of round
This is the safety ground, may be not connected at the generator end

one is Silverish or marked W.. This is the WHite wire

The other two screws are copper colored may be marked with a greek letter and a number or L-1/L-2 or two greek letters. The BLACK wire goes to BOTH of these.

Your problem is that you have connected the safety ground, which is likely N/C (not connected) at the generator, to one of the legs. on the outlet I am guessing.

There are diagrams on NOShockZone if you need them.

Forum Discussion

50-30 adaptor

About Technical Issues

Related Content

30 to 50 adaptor hot?

30 Amp VS 50 Amp

30 vs 50 amp electrical issue help

30 to 50 amp adapter

30 amp camper/50 amp plug and cord