what to do with bx cable without a ground wire???


  #1  
Old 11-21-04, 12:01 PM
cdnatwork
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Question what to do with bx cable without a ground wire???

i'm replacing and old electric baseboard heater in the bathroom of a condo. there is BX cable for the heater, but there is no ground wire. the instructions say i must connect the ground wire to the green screw. the place is about 30 years old, if it matters.

someone suggested connecting a wire from the green ground screw to the metal studs in the wall. good/bad idea?

Thanks for any input!!
 
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Old 11-21-04, 01:18 PM
R
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If you are simply replacing an old heater then you can use the existing wiring. Simply connect nothing to the green ground screw.
 
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Old 11-21-04, 04:25 PM
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As racraft said, you most likely can get by not hooking anything to the ground screw, however you will have better protection if you do. If you have mc cable(bx), and it is securely held in its connector, and the connector has is tight on the metal casing of the heater, that should most likely be sufficient for a ground. You mentioned metal studs, is this a metal or wood framed building? If is it metal, you will have metal boxes so the outer metal jacket of the BX will be a great ground, I wouldn't recommend making a direct connection to a metal stud, as it may not be as good of a ground as the BX jacket. In commercial, when dealing with older buildings that have BX without a ground, we just make sure the connector is tight on both ends of the cable, than you should be fine. Also, older BX cable that only had the hot and neutral wires still had a very thin ground wire in them. It was actually wrapped around the inside of the metal jacket, take a look and see if you can find one. If you do, just take that and bond it to the back of the heater.

Anyways, hope this helps.

Paul
 
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Old 11-21-04, 05:42 PM
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You CANNOT make a ground connection to metal studs. It is against code and a BAD idea. The studs may not even be grounded. They may be grounded but not bonded to the electrical grounding system.

BX is metal armor clad cable in which the armor IS the ground. It may have a thin tracer. This tracer is NOT a ground, never was. It should be wrapped back on the armor and NEVER connected to any ground screw or bar.

If this is what you have just make sure the cable is secure in the connector and the connector is secure in the appliance. Ground completed.
 
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Old 11-22-04, 04:02 AM
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What Petey said, with a couple of additional comments.

Did the heater come with a cable clamp made for AC cable (commonly called BX, but AC is the name used in the codebook)? If not, make sure you replace the cable clamp with a suitable one.

Next, since the metal armor of the AC cable is being used as the ground, then the cable clamp and its jamb nut are being used as the ground connection. Make sure to remove the paint around the hole where the nut grabs, so that it makes a good electrical connection.

The end of the AC cable is sharp and can cut through insulation. Make sure that there is an anti-short bushing (red head) in the end of the cable. This is a little plastic cap that fits down into the cable and wraps around the raw end of the armor. The bonding strip (tracer that Petey mentioned) can be pulled around the anti-short bushing and wrapped around the outside of the armor to hold it in place.

If, for any reason, the cable clamp does not make good electrical connection where it is supposed to, then you can get grounding nuts or bushings. These screw down onto the cable clamp, and have a screw terminal for a ground wire that goes to the correct location.

-Jon
 
 

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