I am trying to figure out how to connect my 240/20a 4-prong outlet from my generator to the three prong dryer plug that was specifically wiring into the main breaker box for a gen. I am aware of all the safety concerns about energizing the street wires etc... I have a main disconnect for that. But I do not know how to wire the 4 prong into a three prong. Help please.

Dave

 

Sorry Dave but what you want to do is both dangerous and a blatant code violation. You need some form of transfer switching, no getting around it.

 

I also agree with Bolted Fault, don't do it.

As an educational opportunity, the three prong old style dryer plug does not incorporate a neutral and separate equip grounding conductor. That is why new dryer plugs have four prongs.
Since the gen has four prongs, it is probably 240/120 requiring two hots a ground and isolated neutral.

 

I have a transfer switch...... and the previous owner had it's input wire to a three prong dryer plug.... so the gen could be stored in the shed etc.... is it possible to do what I want to do? when the gen kicks in the main breaker box is automatically shut out of the system

 

A proper transfer switch for a portable generator will have a recessed male connector for it's input. It will have four connections, for the two hot wires, the neutral and the ground. The transfer switch will switch all three current carrying conductors from the utility feed (usually an output from the main panel) to the input from the generator.

Any other type of connection, such as back feeding through a dryer connection, a stove connection or a 220 outlet is both dangerous and, in many cases, illegal.

Any automatic switchover requires more wires and an automatic start generator, and costs more.

 

There is a form of automatic transfer switch installation that does not require control wires or an automatic start generator. A properly sized contactor that is wired to switch when the generator power is applied does that job very nicely. It transfers on availability of generator power rather than on loss of utility power.
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Tom H

 

What you need is a flanged inlet such as the one shown on page forty of the PDF document at this link.
http://www.hubbell-wiring.com/library/Section-B.pdf
You would then use a twist lock extension cord with one male and one female end to connect your generator outlet to the inlet shown at the link above. The green screw of the inlet is conected to the equipment grounding terminal of the transfer switch. The silver screw of the inlet is connected to the neutral terminal of the transfer switch. The two brass colored screws are conected to the two poles of the transfer switch were that dryer outlet was conected.

If you are lying about there being a transfer switch then I just hope it is you rather than some one else that gets hurt or killed.
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Tom H

 

LISTEN TO THESE ELECTRICAL PROS!
I did a no-transfer-switch emergency generator hook-up last year (no power for about two weeks) as most of my rural neighbors did, because all stores within a 150-mile+ radius had sold out of transfer switches with Hurricane Isabel coming rapidly in on top of us last September.
(Hello John Nelson, who refused to tell me how to hook up my new generator without a transfer switch. I figured it out anyway, but you were RIGHT, as usual!).
***Two out-of-state emergency electrical linemen here to help us were killed by electrocution right after Hurricane Isabel in an adjoining county!***.
THE CAUSE WAS AN ILLEGAL GENERATOR HOOK-UP!
A homeowner, with a generator WITHOUT A TRANSFER SWITCH, had cut-off his main panel breaker, and the line was still apparently energized. He was only fined $10,000, but the families of those two men lost all.
I won't do it again either, although they started using loops over all lines after that.
It isn't worth it. I'll let the freezer food rot, lights and fans out, etc. before I ever jeopardize people again. We all didn't really realize what we were doing, until we heard about those two guys. All of those people (from all over the U.S.) that came to help us, busted their butts for weeks on end to help restore power, and we just didn't realize at the time what we were doing to jeopardize them. Do it right or don't do it at all.
Mike