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Old 02-22-2009, 11:30 AM   #1
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switch lacking ground wire


new homeowner here, and im doing some basic work like replacing switches that arent functioning properly.


specficially, there is a dimmer switch in the master bedroom that doesnt work very well and ive bought a replacement. during the installation process, i discovered that the switch was previously ungrounded. the house was built in 57, and from what ive read this was not uncommon. the box housing the switch is metal, not plastic.

so if someone could advise: what dangers exist if i install this without the ground connected?
is there a way to test if the box itself is grounded?
is pulling a new wire with ground a reasonable DIY job (this may not be a reasonable question without details about the cable run, which i dont have exact knowledge of at the moment)?
how much might a professional charge to do this?


Last edited by anervoustwitch; 02-22-2009 at 11:33 AM. Reason: formatting
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Old 02-22-2009, 03:15 PM   #2
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switch lacking ground wire


Any metal near the electrical source needs to be grounded. Like this metal box. The switch is to be grounded and the box is to be grounded with the grounding conductor in the new cable. They make a grounding pigtail (green wire with a green screw) which will screw into the 10-24 hole in the back of the metal box. Connect all three ground wires by twisting them with electrical pliers and capping with a wirenut. Plastic boxes do not get a ground to the switch which is why both grounded and ungrounded switches are made.

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Old 02-22-2009, 04:24 PM   #3
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switch lacking ground wire


thats what i figured, however given the age of the home, im not certain the box itself is grounded.

any (relatively easy) way to check?
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Old 02-22-2009, 04:33 PM   #4
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switch lacking ground wire


Do you have armored cable like this



Also, if you do have this armored cable (aka bx) than does it have a thin aluminum wire?

BTW a multimeter testing from neutral to box will tell if there is a path, but not if its safe to ground to.
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Old 02-22-2009, 04:47 PM   #5
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switch lacking ground wire


im almost certain it doesnt have that armor around the outside, unless that metal housing does not penetrate the box.
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Old 02-22-2009, 05:42 PM   #6
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switch lacking ground wire


You can put a voltage tester on the hot wire and the box. If it's grounded, it will read voltage.

Just install the dimmer without the ground. For added safety use a nylon cover plate and screws. This will leave no metal parts exposed in case of a fault.
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Old 02-22-2009, 05:48 PM   #7
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switch lacking ground wire


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Originally Posted by 220/221 View Post
You can put a voltage tester on the hot wire and the box. If it's grounded, it will read voltage.

Just install the dimmer without the ground. For added safety use a nylon cover plate and screws. This will leave no metal parts exposed in case of a fault.

I agree 100%
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Old 02-22-2009, 06:38 PM   #8
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switch lacking ground wire


Any is there a lot of fibers or threads and paper where the wires enter the box?
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Old 02-25-2009, 10:29 AM   #9
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switch lacking ground wire


a lovely blurry cellphone shot

basically it looks like the inside has papery material that comes out the end.
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Old 02-25-2009, 10:54 AM   #10
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switch lacking ground wire


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Originally Posted by anervoustwitch View Post
a lovely blurry cellphone shot

basically it looks like the inside has papery material that comes out the end.

Just install the dimmer and use a plastic cover plate with nylon screws as 220/221 said. There is no ground, and no relatively easy way to ground. That thing wrapped around the cable is a thread right? Not a wire?
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Old 02-25-2009, 11:12 AM   #11
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switch lacking ground wire


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Originally Posted by rgsgww View Post
Just install the dimmer and use a plastic cover plate with nylon screws as 220/221 said. There is no ground, and no relatively easy way to ground. That thing wrapped around the cable is a thread right? Not a wire?
the bit at the end? it looked like coppery mesh to me.
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Old 02-25-2009, 11:30 AM   #12
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switch lacking ground wire


That look's like old romex with the ground wrapped around it. (no clamp)
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Old 02-25-2009, 11:39 AM   #13
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switch lacking ground wire


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Originally Posted by hpp58 View Post
That look's like old romex with the ground wrapped around it. (no clamp)
hmm, so does that mean i might be able to ground this switch after all?

what would be the safest way to do that?
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Old 02-25-2009, 01:56 PM   #14
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switch lacking ground wire


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Originally Posted by anervoustwitch View Post
hmm, so does that mean i might be able to ground this switch after all?

what would be the safest way to do that?
Well, I couldn't tell what it was at first (blurry shot)

Normally, you would just un wrap it and nut it with the dimmer ground, but, your going to need to make sure its connected in every box and then test for resistance with ground to neutral.
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Old 02-25-2009, 02:10 PM   #15
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switch lacking ground wire


Quote:
Originally Posted by rgsgww View Post
Well, I couldn't tell what it was at first (blurry shot)

Normally, you would just un wrap it and nut it with the dimmer ground, but, your going to need to make sure its connected in every box and then test for resistance with ground to neutral.
unwrap what?

this is a single switch, there arent any others in parallel for the light it controls.

the breaker this switch is on is basically the upstairs of the house...do you mean id have to check every outlet and switch?

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