I have a new whirlpool dbl oven with a 4 wire wiring harness-white, black, red and green. My old single oven compartments junction box (house was built in '79), has 3 wires-black, white, and copper ground. 50amp, 240v circuit. How do I correctly connect these?
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2How old is the house? Is the circuit breaker double or single? What number on the handle? What was hooked up where the new oven is going to be connected?– TysonNov 26, 2016 at 16:00
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1Does this oven not have a power cord? Also, can you post a photo of the inside of the box where the oven-circuit terminates? Finally, where in the world are you?– ThreePhaseEelNov 26, 2016 at 16:00
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What is the make and model of the oven?– wallykNov 27, 2016 at 7:00
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1Can you please post a photo of the inside of the box here? If you can't post a photo here, just post it to imgur and put a link in the comments so we can edit it into the post...and we need the model # of the oven, too!– ThreePhaseEelNov 27, 2016 at 19:51
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2 Answers
You'd have to look at the old receptacle to be sure. If it's a NEMA 10-50, then the following is true: it is being fed by common 6/2 grounded cable.
NEMA 10 is an obsolete and somewhat dangerous receptacle family, used in the old days for ranges and dryers. It provides hot, hot and neutral - 240V hot-to-hot, and 120V hot-to-neutral. It does not provide ground.
Often, this was installed using the common "/2" cable. There's no choice to color; it's always black, white and bare. In this usage, the white is not a neutral; it's the other hot. The bare wire is the neutral. Really.
Today, a white wire used as a "hot" must be marked with tape. Back in the old days, that was not required if the usage was obvious.
I would make the argument that the old circuit is "grandfathered", which it is. If the 10-50 receptacle broke, you could change it without breaking the grandfathering; in fact the stores sell 10-50R's for only that purpose. I would argue the same is true for changing it to a modern 4-prong NEMA 14-50. I would then use the NEC 2014 rules which allow retrofitting a true ground. Can't promise you the inspector would agree.
answered Nov 28, 2016 at 6:39
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It appears that you might be trying to add a 240V appliance to a 120V supply. A 240V supply will contain Red, White and Black wires typically. The Red and Black are the 120V and the -120V lines, with white being common and bare copper being ground. The green on the appliance will match to the bare copper for Ground. This 3 way wire would have to be connected to a 2 pole circuit breaker, with red on one pole and black on the other.
Unfortunately, I do not think this appliance will work here, it appears you have only 120V supplied.
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You're likely making an incorrect assumption. It's probably old, 2 hots and bare neutral, but that might also be an incorrect assumption, I'll ask a clarification question or two above.– TysonNov 26, 2016 at 15:59
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Interesting thought on the 2 hots and bare neutral. I guess there wouldn't be a proper ground in that case? Nov 26, 2016 at 16:34
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A long long time ago this was fairly common for an oven. Heating element and thermostat neither required neutral, if there was a clock it often had a 240v motor.– TysonNov 26, 2016 at 16:45
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@Tyson, black, white and a bare copper ground for an oven suggest 240V, NOT 120V. The bare copper IS NOT a neutral, it's a ground. This was not always common, it was usually an incorrect installation. This is unless the cable in question was SEU cable, then the bare braided conductor is a neutral and not a ground. Nov 27, 2016 at 19:51
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@SpeedyPetey 240 not 120 was the point of my comment, I was actually became confused about whether the bare copper would be considered neutral or ground as in a main panel it would land the same place, I tried to look up if it would be a neutral or ground as I was writing the comment but the results were not conclusive from 5 minutes of googling, saw it labeled both ways... Anyway my point was to dispute trip0d199's assumption that the white was neutral and that it was 120v 3-wire circuit. As far as popularity it may be regional but every 70's era in-wall oven around here is exactly that..– TysonNov 27, 2016 at 20:17