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Question DetailsAsked on 10/30/2016

Ground wire screw on light fixture

Hi I just purchased a led automatic outdoor light. When setting it up I attached the house ground wire to the green screw on the fixture the only question I have is that under the screw there is small washer type structure. Does the ground wire go in the middle between the head of the screw being on top and the washer type thing on the bottom with the wire in the middle? Or does the washer get pushed up so it is right under the head of the screw and the ground wire is on the bottom? Does it even matter which way it is set up? The directions did not specify so I assume it does not matter either way. Just wanted to make sure. I set it up so that the house ground wire was in the middle between the head of the screw and the washer and it seems to work fine.

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1 Answer


The washer is a wire cinch cup washer - has a rim around about 3/4 of the circumference. Looks something like this though lip is usually less pronounced -

You put the washer on the screw (rim "down"), then start the screw in the hole so it is stable, then wrap the wire clockwise around the screw a full turn plus, holding the washer up ABOVE the wire under the head of the screw - wrap the wire clockwise so when you turn the screw if the washer turns too it tends to tighten the wire wrap rather than spread the wrap out. If one is picky, the wrap where the wire passes by the incoming wire (so full 360 degree wrap accomplished at that point) should pass UNDER the incoming wire and wrap on around a 1/4 - 1/2 turn or so more.

Then seat the washer down on the wire so the part of the edge with no rim (or at the slot if slotted type) sits on the incoming wire so the rim does not cut into it, then tighten down the screw snugly, making sure the wire stays wrapped in under the washer. The reason for the washer (and the rim on it) is to retain the wire inside the rim, and the washer sits still while the screw is screwed in. Without the washer over the wire, the screw tends to try to either wrap up (and possibly break) the wire tighter if it is wrapped clockwise like it should be, or tends to unwrap the wire if it was wrapped counter-clockwise, because the turning of the screw drags along the wire with it when there is no washer.

In a pinch regular washer can be used, but as the screw is tightened down there is a tendency for the wire wrap to expand outwards - the rim on the cup washer avoids that.

Sounds like you put the wire between the screw head and the washer - but if you had a tight wrap and made sure it stayed tight while tightening the screw, especially if you had a full wrap and a half or more, I don't know that I would be so worried about it that I would take it back off to change the washer to being on top of the wire - maybe if you ever take the fixture off for any reason in the future.

FYI - might or might not be of any use to you if you are already done - here are two other very similar threads by anotehr person on putting up outdoor light fixtures and motion sensors which might be of interest to you -

Answered 3 years ago by LCD

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