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Old 02-09-2009, 11:34 AM   #1
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240 to 120 circuit conversion


I have removed my old 240V electric range and have switched to gas. I now have three #8 conductor wires in a metal conduit on a 40A breaker that I would like to convert to 120V. There is no ground wire in the conduit (1960's wiring). Can I run a separate ground from the main supply through the conduit and then set a sub-panel on this circuit or would it be better to pull through a whole new set of conductors? Thanks

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Old 02-09-2009, 11:46 AM   #2
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240 to 120 circuit conversion


*****IF this is metal conduit all the way to the panel*****, the conduit serves as a ground.

Cap off one hot conductor and wirenut a short pigtail onto the other hot and the neutral (white).

Install a short #12 bare ground wire from the box to the 120v recep via a ground screw (there will be a tapped 10/32 hole in the back of the box)


Remove the 2 pole 40 amp breaker and install a single pole 20. Cap off the leg you are not using and install the other on the breaker. If your breaker has a screw terminal rather than a lug, you will probably need to wirenut a short @12 pigtail there too.

Put a panel blank or a spare breaker in the remaining slot. Spare breaker is better. It won't fall out every time you take off the dead front.


Last edited by 220/221; 02-09-2009 at 11:48 AM.
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Old 02-09-2009, 12:34 PM   #3
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240 to 120 circuit conversion


Quote:
Originally Posted by 220/221 View Post
*****IF this is metal conduit all the way to the panel*****, the conduit serves as a ground.
The OP should be able to check for continuity between the conduit ground and the existing neutral wire to verify this since they should in theory be tied together at the main panel.

I would agree with 220/221's plan to re-wire using the existing wires and dropping them to 12 gauge to make the connections to the outlet and breaker. Most 20 amp breakers will not accept wire larger than 10gauge wire, you will just have to look at what your new breaker is rated for.
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Old 02-09-2009, 12:38 PM   #4
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240 to 120 circuit conversion


The OP wants to run a subpanel off this circuit. I would pull a ground in since it's pipe the whole way. I'm not fond of using pipe as a ground (my opinion) especially something 30-40 years old.

I'm just wondering why you wouldn't want a 240 volt sub?
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Old 02-09-2009, 12:40 PM   #5
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240 to 120 circuit conversion


AH - sub-panel, I'd do a 240v sub
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Old 02-09-2009, 12:59 PM   #6
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240 to 120 circuit conversion


Thanks for the advice. I didn't say it but when I said sub panel I meant 240V. I think a sub panel would give me the most options. I am not sure how I feel about using the conduit as a ground either, but that would certainly be the easiest thing to do. I never thought about the 20A breaker not accepting larger wire, that is certainly something to check before I jump into it. Thanks again
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Old 02-09-2009, 02:36 PM   #7
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240 to 120 circuit conversion


A sub panel simply to supply a 120v recep behind the gas range?

A sub panel behind the range?

You're killing me here
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Old 02-09-2009, 02:38 PM   #8
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240 to 120 circuit conversion


And where did he say all that???

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