50 Amp Adapter

[Oonrahnjay]

       OK, I've been offered a chance for indoor storage over the winter at a good price.  The place is wired for 240 service with NEMA 6-50 sockets (I'm pretty sure that it was set up for welding machines).  My shore cord has the four-pin "RV" 50 amp plug but the NEMA 6-50 socket has only three connector pins. 

       It's pretty easy to pick up a 6-50P plug and a 240V RV socket and some 10g power cable.  I assume that the three connectors on the socket are Hot 1 -- Hot 2 -- Neutral.  But how do I make an adapter that includes the ground circuit from the RV plug to ground when going to the three-connector socket in the wall?

       (I often use a 15A, 120V power cord plugged into an ordinary wall socket but, strangely, this location has few 120 wall sockets.  Plus, I guess it would be good to have an adapter to go to NEMA three-connector sockets -- clothes dryers, electric stoves, etc. -- anyway.)

       Any info or advice?   Thanks,   BH   NC    USA

[Len Silva]

The NEMA 6-50 is 240 volts only, there is no neutral. It is HOT-1, HOT-2 and GROUND. That is not going to work for you.

[Oonrahnjay]

    That is not going to work for you. 

     I was afraid that that would be the answer.   It's a good price for winter storage,  so maybe it will be worthwhile to have an electrician install a 4-pin socket.   Thanks for the help,   BH   

[belfert]

It isn't just the socket.  There is probably no neutral wire from the panel to the socket so that would need to be added.

[Len Silva]

Assuming it's all in conduit and not too far from the panel, it shouldn't a big job to pull in a neutral and replace the socket.
If it's something you are going to try yourself, don't attempt to just add the neutral.  Pull out the three wires and then pull in the four wires.

[Oonrahnjay]

  Assuming it's all in conduit and not too far from the panel, it shouldn't a big job to pull in a neutral and replace the socket.   If it's something you are going to try yourself, don't attempt to just add the neutral.  Pull out the three wires and then pull in the four wires.   

      Yeah, it is a fair distance and across a couple of walled-in storage bays from the panel.  I can live with 15A/120V for the winter - I don't think I'll need more than enough power to float charge the batteries and give me a little lighting when I visit to take care of things.   

       Thanks for the help, Len.  It's very practical and the advice and explanation is exactly what I needed (even if it wasn't what I wanted to hear  ).

[bevans6]

Don't let anyone tell you ground is the same as neutral and we'll just wire you up a four prong outlet with ground tied to neutral...  It's happened...

Brian

[gumpy]

Don't let anyone tell you ground is the same as neutral and we'll just wire you up a four prong outlet with ground tied to neutral...  It's happened...

Brian

I'm certainly not going to tell him it's ok to do that, or that it in any way meets code, but if you were to open the panel, you would find that ground and neutral are probably
connected together on the same bus bar, so, if one were to tie ground to neutral in a pigtail to connect the bus up for winter, that cord certainly isn't
going to know the difference, and neither would the bus. Nothing in the bus depends on neutral being separate from ground.


Of course you always could buy a good length of 6-3 w/g and snake that over the walls and hook it directly into the panel with your 3 prong w/g twist lock
plug on the end.

[Oonrahnjay]

   Don't let anyone tell you ground is the same as neutral and we'll just wire you up a four prong outlet with ground tied to neutral...  It's happened...   Brian   

      Somebody just tried to tell me that less than an hour ago (the storage location owner, who has no idea whether or not they're tied together as Gumpy described -- which is, of course, a game changer).  I politely demurred.  I may spring for an electrician; if he tells me that the neutral and ground are indeed tied together already in the building wiring, I may make up an adapter with the neutral and ground joined at the 6-50P plug.  But that will negate the idea of having an adapter that I can use anywhere else that I might need it (I'd never know if the ground and neutral were bonded together in the system at any other place).

      As I said, a 15A 120V cord will meet my minimum needs over the winter so I'll probably stay with that.   Thanks to all for your input,  BH  NC  USA

[gumpy]

     
      As I said, a 15A 120V cord will meet my minimum needs over the winter so I'll probably stay with that.   Thanks to all for your input,  BH  NC  USA

Probably a wise decision.

The other problem you have to consider with the current feed and a homemade adapter is the size of the ground wire in the feed. The ground wire
might be much smaller than the hot wires. Since your coach is wired for 120v, all of your needs require the neutral, so the size of the conductor might
be a concern.

[bevans6]

The other thing about ground, besides that it might be smaller, is that it might not be there at all as far as an actual wire goes.  Depending on how old the building is the ground might be the metallic conduit or the armoured sheath if it's flexible metallic cable.  Only by looking at it can you tell what's what.

Brian