Hope I can ask this clearly. I am in New York State. I just got a backup generator, my other one died. I use it only to power a sump pump and 2 refrigerators during blackouts. My new generator however has two plugs...one is a 120v 3 prong, the other is a 120/240v 4 prong twist and lock. There is a switch on the generator to have power outage be 120 or 240..again I would only use 120v. My question/problem is all my extention cords (mostly 20 amp 3 prong ones) will not plug into the 120/240v plug. Is there an adapter to convert my 3 prong to a 4 prong, which would allow me to run the generator in 120v mode and thus use both plugs? OR..the generator came with 4 prong plug for the outlet (not cord though). Should I cut the end off one of my extension cords (outdoor type) and connect it to that 4 prong plug...if so..what is proper connection of wires inside the plug, is it blk to blk, white to white sort of thing? I think you get the drift of what I'm trying to do..what is best way.

What is the breaker rating of the 120/240 twist lock plug? For 15 or 20 amp receptacles the maximum rating if the breaker is 20 amps.

You don't need the twist lock plug if only use 120volts. Use only the 120 volt receptacle.

Yes, you can get an adapter that will split your 240 into 2 separate
120 volt lines. This way you will be able to use both phases at the
same time. If this is a smaller generator you may have a 30 amp
120v twist or rv style plug in addition to your other plugs, this is
what your 120/240 switch is for. It allows your windings to operate
in parallel so the generator is at full power. You don't see this
switch that often any more but it's great for rv use.
If you use an adapter the switch will stay in the 240 mode.
Wiring a 240 plug to operate on half phase is not a good
idea, besides the cost of a new plug would be almost as much
as the proper adapter.

Jim

I realize I can just use the 120v plug, but I wanted to use both so i can run one cord to my pump and downstairs refrig and use the other plug to run a cord to my upstairs refrig.

Obviously I'm no electrician so ya lost me just a bit . The way I used my previous generator which had 2 120v only plugs was to run one cord to my basement from one plug (which ran my sump and a refrig) and the other cord upstairs from the other plug (which ran a refrig and small TV and lamp). Now I have this with a 120 plug and a 120/240v plug. Should I run this new gen in 120 and just run everything off the single 120V outlet and just disregard the 240v outlet? Or if I get the adapter you talk about should I then put one cord into the 120v outlet another into the adapter you recommend and then RUN THE GENERATOR IN 240V mode??? I was thinking of doing the following...running the genertor in 120mode. Take the 240V plug they provide and running and wiring a 3 wire cord (picking up one blk to blk, leaving other blk alone, one neutral to neutral and grnd to grn) to a box and plug and using that as my 2nd 120v outlet and running the generator in 120V mode?? What ya think?

What brand? What do the instructions say? The sales people should be able to answer your question. Every genset is different.

It would be good if we could see a picture of your front panel or write
the specs that came on the box.

It is not necessary nor wise for you modify your wiring.

This sounds like a larger generator, if your last one a had duplex
recptical for two extension cords, the new one should have
the same set up. If you want to run more than two cords then
go to a place like home depot and ask for an adapter.

As long as you use unmodified plugs and cords you can see
what works the best.
Jim

I will the describe the generator in FULL detail. It is a 3500 watt electric start generator, with 3000w "normal" output, 3500W peak output. The details are as follows:
--it has a switch to run the gen in either 120v or 240v mode
--it has a plug/receptical labelled 120V, normal 3 prong plug, with a 20 amp breaker
--it has a plug/receptical labelled 120v/240, 4 prong twist plug, with a 30 am breaker
The manual is VERY poor on description other than saying this, "both plugs may be used simoultaneously. If you maximize the first 120v receptacle you may use the second".
THAT is exactly what I would like to do...BUT...it is a 4 prong plug and all my extension cords are 3 prong, 15amp cords..all I want to do is figure out a way to use the 2nd addition plug and get around the darn 4 prong requirement..and i'm not sure if when I use the second plug if my switch should be in 120v or 240v position...since if I use the second plug at 120v, in addition to the first plug as 120V this really is 240V total!.

Post make and model so we can look it up.