Ungrounded branch circuits

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czars

Czars
Location
West Melbourne, FL
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Florida Certified Electrical Contractor
I have a client with an older house where none of the branch circuits are wired with grounded cable. What are the options for adding grounds to the circuits other than re-wiring? I can't find the code section that addresses this situation. Can someone ID that also?
 
Is it wired with 2-wire AC cable or 2-wire type NM? If it is AC cable the metallic sheath is recognized as a ground. For replacing receptacles see 406.3(D).
 
haskindm said:
Is it wired with 2-wire AC cable or 2-wire type NM? If it is AC cable the metallic sheath is recognized as a ground. For replacing receptacles see 406.3(D).
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You have to be real careful there based on the age of the wiring. The older AC Cable (BX) did not have a bond strip and the steel outer jacket did not provide an adequate ground, in fact, just the opposite. In the event the jacket was called upon to carry a fault it would become a heater, possibly a VERY HOT heater, due to the high resistance.
 
augie47 said:
You have to be real careful there based on the age of the wiring. The older AC Cable (BX) did not have a bond strip and the steel outer jacket did not provide an adequate ground, in fact, just the opposite. In the event the jacket was called upon to carry a fault it would become a heater, possibly a VERY HOT heater, due to the high resistance.
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Good point. The bonding strip was required in 1959, I think, and it may be that tests of older ac/bx commonly have shown a resistance of 3 ohms / 100' or more, if I am remembering it correctly.
 
Oy yeah, you did say that it was a grounded cable but I overlooked that part. Is it full-sized or smaller than the other conductors? I think it was '65 or '68 before a full size was required for small cables.

Is it brought fully into the boxes or wrapped back around the cable sheaths such that it is difficult to unwind without some damage?
 
augie47 said:
The older AC Cable (BX) did not have a bond strip and the steel outer jacket did not provide an adequate ground, in fact, just the opposite. In the event the jacket was called upon to carry a fault it would become a heater, possibly a VERY HOT heater, due to the high resistance.
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I have seen in a remodel the 2x4 stud charred from the old BX.
 
I would not continue a circuit from an existing circuit that is not grounded. It would be a violation of the NEC. You need to rewire if you want to add more outlets.
 
Install GFCIs. Mike Holt once said
"A two wire system protected by GFCIs is safer than a three wire grounded system" . Think about this and you will understand why.
 
DetroitEE said:
So that section doesn't permit just taking an equipment ground from the nearest box, it says you have to go all the way back to the panel or the grounding electrode, correct?
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2008 NEC
250.130 Equipment Grounding Conductor Connections.

. . . For replacement of non?grounding-type receptacles with grounding-type receptacles and for branch-circuit extensions only in existing installations that do not have an equipment grounding conductor in the branch circuit, connections shall be permitted as indicated in 250.130(C).
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If there is no EGC (equipment grounding conductor) in the branch circuit, going to the nearest box won't help.

The new grounding type receptacle ground terminal must have an EGC that is electrically continuous, assembled out of the choices listed in 250.118, which goes all the way back to one of the choices in 250.130(C).

If the occupancy has a mixture of branch circuits / feeder circuits where some contain intact EGCs and others do not, one can make use of the existing, nearby EGC, that is connected to the choices in 250.130(C), if in compliance with 250.122.
 
Dennis Alwon said:
I would not continue a circuit from an existing circuit that is not grounded. It would be a violation of the NEC. You need to rewire if you want to add more outlets.
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If you did it per Exhibit 250.52

DetroitEE said:
So that section doesn't permit just taking an equipment ground from the nearest box, it says you have to go all the way back to the panel or the grounding electrode, correct?
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See above statement.

tom baker said:
Install GFCIs. Mike Holt once said
"A two wire system protected by GFCIs is safer than a three wire grounded system" . Think about this and you will understand why.
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I agree but have added the EGC per the owners request.
 
Note that 250.130(C) does not let you 'just' connect a EGC to the closest waterline. The connection must be made in the 5' section (250.52(A)(1)) before the attactment of the GEC.
 
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