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rivers001 03-04-2011 02:35 PM

Replacing metal box caused issues
 
Good afternoon,
I am looking for help with a problem as I am a total newbie to electrical projects.

Here is the scenario: I had an existing metal box which has metal conduit attached to it from bottom and top. Bottom contains the hot wire which then feeds recessed lights on top.
I replaced the existing wall switch with a new timer and found that it would not fit in the existing metal box. I bought a deeper plastic box and replaced the metal box with it. After this, the recessed lights did not turn on. I noticed that my "pen" voltage tester now detects current throughout the metal conduit leading up to the recessed lights. I am assuming that by removing the metal box, I have a ground problem?
Inside the metal conduit there is only the hot wire and the neutral but no ground.

Any clues on what is going on?

Thanks,
Angel

teamo 03-04-2011 03:22 PM

By removing the metal box you have likely removed the ground path. That should not have any affect on the operation of the circuit. A ground is used as a separate path back to the panel should a fault occur within the circuit. Don't rely on those non contact voltage testers they sometimes pick up stray current and give false readings. I would start by removing the timer switch that you installed and test for voltage at the hot wires with either a neon type tester or a volt meter. also you should replace that plastic box with a metal one to restore the ground.

rivers001 03-04-2011 03:39 PM

Thanks - Here's another observation. I tested with the volt meter and assured that voltage was present at the switch. Here's what I found:

1. I tested the hot wire going into the switch - Power is ok.
2. I connected the switch, turned it on, and test the "out" wire on the switch to assure power was flowing through - power is ok.
3. I connected the "out" wire I just test in step 2 above to the wire going to the recessed lights. As soon as connect it, there is no power. I remove the connection to the fixture and there is power again.
What would cause this?

Jackofall1 03-04-2011 03:44 PM

Quote:

Originally Posted by rivers001 (Post 602349)
Thanks - Here's another observation. I tested with the volt meter and assured that voltage was present at the switch. Here's what I found:

1. I tested the hot wire going into the switch - Power is ok.
2. I connected the switch, turned it on, and test the "out" wire on the switch to assure power was flowing through - power is ok.
3. I connected the "out" wire I just test in step 2 above to the wire going to the recessed lights. As soon as connect it, there is no power. I remove the connection to the fixture and there is power again.
What would cause this?

If what you are saying is, when you connect the "out wire" to the switch with the switch on, there is no voltage....correct?

Try that same measurement with the switch off

teamo 03-04-2011 04:01 PM

Is this a mechanical type switch or an electronic switch?

rivers001 03-04-2011 04:15 PM

With the switch in the off position, electricity does not flow through it so there is no power on the "out" side. Power does flow through it just fine without the fixture connected to it. The problem arises as soon as I connect the wire of the fixture to it.

This is a dimming switch. I eliminated the switch as being the problem by swapping it out with a working one.

Jackofall1 03-04-2011 04:26 PM

Rivers, I am quite aware as to how a switch works, I was asking to ensure you know how voltage works, voltage measure across an open switch will read line voltage, voltage read across a closed switch will read 0.

Voltage read between a closed switch the end of one wire disconnected from a load to the load wire will read line voltage.

My guess is you either have a bad timer switch, or you didn't wire it correctly.

Mark

a7ecorsair 03-04-2011 05:45 PM

Quote:

Originally Posted by rivers001 (Post 602349)
Thanks - Here's another observation. I tested with the volt meter and assured that voltage was present at the switch. Here's what I found:

1. I tested the hot wire going into the switch - Power is ok.
2. I connected the switch, turned it on, and test the "out" wire on the switch to assure power was flowing through - power is ok.
3. I connected the "out" wire I just test in step 2 above to the wire going to the recessed lights. As soon as connect it, there is no power. I remove the connection to the fixture and there is power again.
What would cause this?

You are using one meter lead to test for power at various points. Where are you connecting the other lead? Since you upset the ground circuit, your one meter lead will have to be connected to the neutral wire that would be coming in along with the hot wire at the bottom of the box as you have pointed out. This neutral should also be connected to the neutral leaving the box and going to the lamp.

AllanJ 03-04-2011 06:08 PM

There may be a long standing mistake in the original wiring whereby the conduit was used as a neutral.

So do not touch the conduit with bare hands for the time being. For kicks, measure voltage between the two conduit ends as they enter the plastic box. Or, if you are daring, turn the switch to on and, with one hand in a pocket, get a piece of wire to bridge the two conduits for a minute or two. If that lights the light then you definitely have a ground fault (hot or neutral touching the conduit.

After that, keep the breaker off until you find and eliminate the accidental or intentional connection between neutral and ground.

rivers001 03-04-2011 07:55 PM

Thanks for all the input guys.
AllanJ - I tested voltage between conduit ends and found a reading of 70 to 75 with the switch off. When I turned on the switch, the reading went up to 110 to 115. I wasn't daring enough to bridge them by holding the wire. Can I get the same result by taping a wire to both ends with electrical tape?

Mark, I've tested that switch with another one in the house by swapping it. Wired it the same way and it worked in another location.

-Angel

a7ecorsair 03-04-2011 08:04 PM

Do you have two wires in each conduit?

rivers001 03-04-2011 08:22 PM

Yes, I have two in there.

a7ecorsair 03-04-2011 08:32 PM

Quote:

Originally Posted by rivers001 (Post 602555)
Yes, I have two in there.

OK.
Then:
One wire from bottom conduit is connected to switch
One wire from top conduit is connected to switch
The other wire from the bottom conduit is connected to the other wire in the top conduit.
Is this correct?

rivers001 03-04-2011 08:57 PM

Yes, that's is correct.

a7ecorsair 03-04-2011 09:48 PM

Quote:

I replaced the existing wall switch with a new timer
Is this a mechanical timer? If it is an electric timer it will require a connection to the neutral.


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