Wednesday, May 27, 2009

Subject: 30 amp plug

Name: Steve

Question: Hi I had an electrician put in a transfer switch so I could plug my motorhome's 30 amp 120 v generator into the house and use the power during a power outage. Coming out of the transfer switch box are three wires, a white, black and another black wires. These wires go to another box that houses two breakers. Coming from the transfer switch, the two black wires go to the bottom of each of the two circuit breakers. The white wire from the transfer switch is connected to a bar where it connects near the top of one circuit breaker. Connected to this same bar is the white wire going to the plug. Also connected to this same bar is the brass (uninsulated) wire also going to the plug.
On the left side of the box, a red wire goes out to the plug. On the right side of the box, a black wire goes out to the plug.
I had to replace the plug because it was crushed. I cut the cord going to the plug for a fresh set of wires to replace the plug.
The plug has a round prong on the top. It has two flat prongs at 45 degree angles. This is the same type of plug that was originally on the wire. The directions from the plug says to connect the green wire to the top round prong. The other two prongs are supposed to have the black and white wires attached.
My question is, I do not have a green wire to attach to the round prong. Which wires should go where?
Is there a way of figuring this out? Any help you can offer is appreciated
The attached photo shows the breaker box. Wire coming up from the bottom originate from the transfer switch box. The wires going upward are the ones going the plug that will plug into the generator.
Thanks :)

Answer: Hi Steve,

Do you have the old plug? The one you cut off. The wires go exactly in the same order as the old switch.

If you do not have the old switch the here is what it looks like you have. The round plug is your ground. The wire that attaches to that goes to your ground bar. It look to be either a bare copper wire or a white wire. The flat prongs are your hots. The go to your breaker. They look to be either black or red. The order of the hots will not matter.

This maybe a job you want to call in an electrician for. There is enough power there to be dangerous if you do it wrong. We don't have many motor homes here in Philly but if it have all the things a normal home has you could be dealing with a large load. Be careful.

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