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220 extension cord

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Feb 12, 2014, 09:41 AM
220 extension cord
Hello. I would like to be able to use the 220 wall heater in our sunroom during a power loss. My emergency generator has a 220 receptacle for four prongs. The heater has a three prong plug.

I have purchased a four prong plug for the generator, a three prong receptacle for the heater, and 18' of four wire 10 gauge cord. Would the correct way to build the extension cord be to leave the neutral (white?) wire unconnected? I'm obviously a neophyte when it comes to electricity but respectful enough of its consequences that I want to proceed with caution and confidence.
Feb 12, 2014, 01:22 PM
220 volt entrance feed (power that looks like the utility when you put it into the generator bypass panel) will have phase-1 black, phase-2 red, white neutral, and green safety ground. the safety ground is supposed to be separate from neutral everyplace but at the entrance panel. generator manuals usually suggest strongly staking a ground rod by the power plant and connecting it to a ground bolt at the generator.

a standard 220 volt appliance, like your heater, have phase-1, phase-2, and neutral, like your plug. if this was a strip heater, I would expect ground to be to the metal frame. your cord and plug are really not a special wiring trick without a separate ground wire.

correct way to go about this would be place a 4-wire cord on the heater and make the appropriate interconnection. what is likely is you will connect red to red, black to black, white to white, and let the case float. I would rather connect the white and green together and take them to the neutral lug for the heater connector at this point, but that means you have absolutely GOT to ground the generator for any degree of safety.

if you are in the "historic ice event" weather area now and don't have time to plan ahead much, that's the plan. good luck, make sure to tarp the generator overhead and into the wind, best to put it on a couple pallets so it doesn't freeze in.

the REAL plan is to cut in a correct generator bypass breaker panel and wire to it according to the codes, which is generally regarded as call the electrician stuff. you won't get an electrician out if the ice is falling now and the trees are coming down.

folks do walk away from a 120 volt hit, but rarely do from 240 volt electrocutions. one way or another, that ground has got to be there.

This message has been edited. Last edited by: swschrad,

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Feb 13, 2014, 04:35 AM
While I very much appreciate the response you may have to dumb it down a tad. Your discussion of a generator bypass panel suggests to me something permanently installed. I have a gasoline powered portable emergency generator that can be wheeled from storage. It accepts a 4 prong 220 plug as well as 110 plugs. Assuming that I have no desire to change the 3 wire pigtail on the sunroom 220 heater . . . is it possible to make a 220 extension cord to accommodate the 3 prong pigtail and 4 prong receptacle? Hope that clarifies the original question.