4-wire dryer receptacle question

17 years ago

Ok guys, I'm baaaack. After finding that the receptacle boxes in my basement are not grounded I began grounding them to bare wire in the cables. Then I found that the 4-hole dryer recptacle wasn't grounded either so I pigtailed a #10 bare wire to the bare wire which is connected to the U shaped hole at the top of the receptacle and fastened the other end to a screw in the box which I painted green. When I turned on breaker to the recptacle with the dryer plugged in I heard a snap which sounded like an arc. I turned the power back off and pulled the plug. It had a smudge of black soot on the tip end of the L shaped blade at the bottom which connected to the white neutral wire. Not knowing what I may have done wrong I took it all down and put it back together again making sure all connections are tight and all wires are on the correct blades according to the wiring diagram of the receptacle in the dryer's installation booklet. When I turned on the power again there was no snap and the dryer worked as it should so I thought I had it right.

Now the plot thickens again. Reading both the little that Wiring Simplified has to say about dryer receptacles and the installation instructions that came with the appliance I couldn't find any mention of grounding the receptacle box. So I went into the box again and checked everything carefully. As far as my very limited knowledge goes I don't see any reason why grounding the box in that way should cause the neutral blade to arc like it did and yet everything else is like it should be according to the dryer's installation instructions. So I turned the breaker back on with the plug out and then plugged it in again. Again there was a snap sound when I pushed the plug in and when I pulled it out that same neutral blade was smutty again at the very tip end. When I turned the breaker off and on a few times with the dryer plugged in there was no further snap or smut on the blade and the dryer runs perfect. Can somebody please tell me what I'm doing wrong or not doing right? I'm no professional but I do know how to make good tight connections and can do neat work in boxes and such. Is there a problem with grounding the box the way I did or is it better to just leave it like it was before I started messing with it? I'm sure some of you guys are getting tired of my unending questions but I can't find the answers I need anywhere else but here.

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Comments (4)

empjr
Original Author
17 years ago
Just to make it clearer ( I hope) the wiring diagram shows the red and black wires on the flat blades at both sides of the plug, the white wire on the backwards L-shaped blade at the bottom, and the bare ground wire on the U-shaped blade at the top. The receptacle and the plug are both wired according to the instructions in the dryer's installation booklet. The ONLY thing I changed in the set-up was adding the pigtail from the bare ground wire over to the grounding screw in the box.
normel
17 years ago
Check for a loose strand of wire that may be contacting the box intermittently. My guess is that grounding the box may not have caused the problem, but the repeated taking the receptacle in and out may have. How big of a box is present? It should be a deep 4" square for best results.
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bigbird_1
17 years ago
" It should be a deep 4" square for best results."

The box should be a 4 11/16" square designed for dryers or stoves.
empjr
Original Author
17 years ago
The box is 4" square and about 2" deep which is kind of crowded with that large receptacle and 4 very stiff wires. I may replace it with a 4x4x4 deep box if it's available.
I don't see any stray strands of wire that could be touching the box, all the wires in there are #10 solid copper wire, and all bare copper except the ground is enclosed in the receptacle lug holes. The box isn't hot, and a test light lights up between the red wire slot and the white neutral slot and between the black wire slot and neutral. When tested with the power off there is no continuity between either hot wire slot and the ground slot, but there must be some contact somewhere between the neutral and ground because a multi-tester shows roughly 12-15K ohms resistance between those slots. Would that be because the ground and neutrals are joined in the breaker box? I can't see how they could be touching anywhere in the box or at the receptacle. I tried pugging in the dryer this morning a couple of times and there was no snap sound and no smut on the neutral blade, but nothing has been changed or messed with in the box since yesterday. I just wish I knew if it is safe to operate the dryer since my wife will be needing it Monday.

4-wire dryer receptacle question

Comments (4)

empjr
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normel

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4-wire dryer receptacle question

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