US generator wiring help please?

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  • I've been given an american 3.3kw diesel genny but i can't figure out how to wire it up! It has two outputs, one is 110v and the other is 110/220v which is the one I want to use. It takes a 4 pin nema plug which is the bit that confuses me. From what i can work out there are two 'hot' wires, an earth and a neutral. Using one hot and the neutral gives 110v and using both hots but no neutral gives 220v? What i can't figure out is how to connect an extension lead to the output so that i can charge batteries, run power tools, etc. Would i use one of the hot leads as an earth? I really don't want to fry myself, my truck or anything else so any help would be appreciated :-)

  • If you have the makers' name (Onan maybe?) I wonder if you could email them to get a definitive answer? Most of these manufacturers have helplines for just this sort of purpose. American wiring can be quite strange to us Brits, as I know to my cost having fitted bathrooms there for a couple of years and got into a right lather over the apparent seven white wires and one black, or whatever it was!
    Hope to hear soon that you're up and running

    Not a shred of evidence exists in favor of the idea that life is meant to be serious.

  • Thanks for your reply :-) The engine is a robin dy27 but the genny bit is a power gard made by osh kosh. It's several years old but had been used for less than an hour from new! I changed the oil, ran it for 30 mins then changed the oil again. It's not very quiet but runs sweet. I think Robin is owned by Subaru now but i could email them and see if they reply.

  • sounds like the genny is using a centre tapping to give 220v, a common setup in the us, take 2 phases off the 110 circuit and pair them for 220, just be aware that the frequency will be 60hz instead of our 50hz, so things will run a little faster

  • To be honest get a professional to look at it.
    The 60hz can be reduced to 50hz by altering the engine speed.
    Ask said professional about earthing too as its vital for any protection devices to work

  • I'd check all your appliances. A vast number of things accept a wide range of input voltage these days, usually 90-250
    You may be able to just use 120!


    Good point, you can easily but 110v light bulbs too as the are used on building sights etc due to the risk of electrocution being less