Generator cable sizing and connectors


Old 08-22-09, 09:03 PM
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Generator cable sizing and connectors

I would like to get a 50A inlet and have that wired to the panel in case I eventually upgrade my 20A generator. I will likely end up with a 30A gen long before that but i'm curious if I can get a 50A inlet, 50A cable, and mate with a 20A male to hook to the gen, or are the wires too large for the 20A male?

Option B is 50A wiring to the inlet box, and using a 30A inlet, 30A cable and switch the male end to a 20A for the gen, or is the 50A wires too large for the 30A inlet box?

Plan B seems more practical since a 50A gen is a longshot and if that time comes I will just get a 50A cable.

I have seen 3 and 4 prong 50A inlet boxes so which on is used for gen use?

I know that if I use all 20A hardware I will end up with a 30A gen find the next day .

Option C is route wire for a 50A gen through conduit from the panell along with the 30A wire and just swap out the inlet box when the time comes for the 50A gen and then use the 50A wire.

I assume the connectors have some slight "wiggle" room to use larger wire but I do not plan on overloading any circuits to accomplish this.

I will use a smaller gen with larger wire but not the other way case anyone was wondering.
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Old 08-22-09, 09:14 PM
Join Date: Mar 2006
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Run #6 conductors (2 hot and 1 neutral) from the transfer switch (or generator circuit breaker if using a panel interlock) along with a #10 equipment ground to the power inlet box. (All conductors are type THHN/THWN copper)

The flexible cable from the generator to the inlet box would have to be a type S (or S with other letters) four-conductor and most likely #6 conductors for use at 50 amperes. It is highly unlikely that you could ever find a 20 ampere plug that would allow for #6 conductors. The easiest would be to install a fifty ampere plug on the cable and then add a fifty ampere receptacle to the generator.

Alternatively you could use a cable more appropriate to the generator you have, either a 12-4 cable for twenty ampere service or a 10-4 cable for thirty ampere service, and add a fifty ampere connector to match up with the power inlet box.

By installing the #6 conductors from the power inlet box to the circuit breaker or transfer switch you are covered no matter what generator you use.
Old 08-22-09, 09:37 PM
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You would use 4 prong/wire.

I would install a 50A inlet, and get a 50A female and 20 or 30A cap and make a 20/30 to 50 adapter, and use a 20/30A generator cord, or a 50A genertor cord.

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