Open Ground Indicated

Old 07-08-02, 08:22 AM
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Open Ground Indicated

In changing some kitchen switches/receptacles I tested one of the receps with circuit tester and got an "Open Ground" reading. Haven't opened the walls but it appears most of wiring is BX. Other circuits in apartment read okay when tested. What is practical impact of open ground message and is there a way to test to determine the point of the fault/break.
Old 07-08-02, 06:20 PM
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The older BX cable you are pointing out was commonly a two wire cable with a black and white wire only in it. The wiring back when BX cable was originally installed it met Code to install a 2 wire branch circuit without a ground. The NEC still recognizes this two wire system to be used in existing buildings if they met Code at the original time of construction. If the above is true then you don't have to do anything.

There is a place in the NEC that allows you to replace the two prong plugs with three prong plugs but you must then either install a GFI protection for that three prong receptacle with a tag on that receptacle saying GFI protected. YOu may also run a single green insulated equipment grounding conductor from that receptacle back to the panel to create an equipment grounding system for that receptacle. You may also replace the old BX cable with a new Romex cable creating a replacement new branch circuit with an equipment grounding conductor to replace the old BX cable.

Hope this helps

Old 07-09-02, 04:36 AM
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Not sure if this is the proper way to further pursue issue or not but....
Regarding older BX cable-- I always thought that if metallic connectors, boxes, etc. were used and all connections tight the protective metallic covering on the BX would serve to "ground" the circuit by tieing it back to the panel eventually just as with EMT. Didn't think there was a need to run a third or separate ground wire even if using an updated receptacle.
Old 07-09-02, 05:39 AM
bungalow jeff
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Since my house has every known form of wiring in it, I can confirm that older BX cable does not provide a ground. I think it is because of the coiled make-up of the sheathing. The only BX reading a ground is the later kind with a distinct ground wire.
Old 07-09-02, 05:52 AM
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A BX cable should provide a good ground if installed properly, even without the ground wire.

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