AC cable w/ bonding strip?

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Old 09-12-13, 03:36 PM
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AC cable w/ bonding strip?

Hello All - hoping someone can help me clarify.

I've begun replacing a bunch of 2 prong outlets in my home to 3 prong. I've done a lot of research and it sounds like the correct way to do this (other then running new grounds from all the outlets back to the circuit box) is to connect a ground wire directly to the back of the metal outlet box with a green screw. This will only work if the box is grounded.

I tested the boxes and they are indeed grounded (multimeter with red it hot and black to the box shows 120).

Good so far....now my question. I've read that this method should only be used on AC cable that has a bonding strip.

Is there a way to determine this easily? For the life of me, I cannot figure it out. On the actual AC cable, I do not see any bonding strip on the outside. Within the outlet, there is a clamp where the two wires come in, but I don't see any bonding wire (although its very difficult to see).

I also took off the circuit breaker cover. The AC cable comes up through the bottom of the box, is clamped on by a metal ring to the actual box, and inside the two wires (black and white) go into the circuit breaker box. No sign of the bonding strip there either.

Am I missing something and the bonding strip is usually difficult to see? The house was built in 1957 (I believe grounded AC cable was required beginning in 1959).

The outlet tested shows "correct" on the outlets I've replaced. Would it still show correct if there was no bonding strip?

Sorry, lots of questions, but hoping to clarify. Want to maker sure I'd doing this correctly and more importantly, safely.
 
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Old 09-12-13, 04:07 PM
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Whether the cable in your house has a bonding wire or not, It sounds like it is providing an adequate path to ground, as shown by your test. I would go ahead and change out the receptacles.

The bonding wire is usually looped back over the anti-short bushing and wound into the spiral groove on the outside of the cable for a couple of inches. It is very difficult to see inside the box, if it's possible at all. And who cares? The purpose of that wire is to insure an adequate path to ground. You can have a pro load-test the wiring for that if you want to.
 
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Old 09-12-13, 04:26 PM
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Nashkat1. - thanks for the response

I've read that ac cable without a bonding strip is not considered an adequate ground since if there's a short, the actual metal wiring cover can heat up pretty significantly. Ac cable with the strip apparently does not do this. Is that not the case?

New to this, trying to understand what's correct and what's safe
 
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Old 09-12-13, 04:44 PM
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One other question, is the bonding strip connected to the ground/neutral bar in the circuit breaker box? Or is it usually connected the same way as the outlet (over anti short bushing and into spiral groove)?
 
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Old 09-12-13, 05:33 PM
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With metal conduit and metal boxes, the equipment grounding conductor is the conduit and a "ground wire" is not needed. But all the parts need to be properly connected and properly torqued to ensure adequate bonding at each joint.

Receptacles etc. are bonded to the respective metal boxes using pigtails.

Except taht spiral flexible conduit is not a sufficicent grounding conductor unless a ground wire or metal strip runs lengthwise through it, touching the spiral i.e. running outside any paper lining. This strip need not come into each outlet box and be fastened to or pigtailed to receptacles, etc.

The end of the bonding strip should be visible in the conduit where the current carrying conductors emerge into the box. If you don't see a bonding strip then you will have to assume that there isn't any and you will need to string through a ground wire that is connected up in the same fashion as the ground wire in Romex cables. Just one ground wire is needed in a conduit and it is sized to go with the largest current carrying conductor in or sharing that conduit.
 
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Old 09-12-13, 05:42 PM
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"Except taht spiral flexible conduit is not a sufficicent grounding conductor unless a ground wire or metal strip runs lengthwise through it, touching the spiral i.e. running outside any paper lining. "

That is my understanding as well, but how can I determine if my spiral flexible wiring has this? I can't see it in the outlet box, behind the outlet box (I have access to the back on a couple walls or within the circuit breaker box.

My understanding is sometimes its just cut or wrapped right as it enters the outlet box
 
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Old 09-12-13, 05:46 PM
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It's very difficult to see where the wires enter within the outlet box. To make matters worse, there seems to be a clamp that covers where they come in. The actual wires entering the box are behind the clamp. Makes seeing the bonding clip very difficult if it does exist
 
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Old 09-12-13, 06:34 PM
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Hmm, finally found one outlet that did not have a clamp covering the incoming wires to the outlet box. On this one, I see a very thin silver covered wire coming out with the black and white wires. The silver wire immediately makes a V and goes back into the connector. Bonding wire?
 
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Old 09-13-13, 10:36 PM
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One other question, is the bonding strip connected to the ground/neutral bar in the circuit breaker box? Or is it usually connected the same way as the outlet (over anti short bushing and into spiral groove)?
It is not a grounding conductor and is never bonded to ground. It is treated the same way at every junction, including the one at the panel.

It's very difficult to see where the wires enter within the outlet box. To make matters worse, there seems to be a clamp that covers where they come in. The actual wires entering the box are behind the clamp. Makes seeing the bonding clip very difficult if it does exist
Remove the clamp, have a look, and reinstall the clamp.

Hmm, finally found one outlet that did not have a clamp covering the incoming wires to the outlet box. On this one, I see a very thin silver covered wire coming out with the black and white wires. The silver wire immediately makes a V and goes back into the connector. Bonding wire?
That's what it sounds like. Not terminated in the standard way, but probably very difficult to correct.

Can you post a picture of that one?

I've read that ac cable without a bonding strip is not considered an adequate ground since if there's a short, the actual metal wiring cover can heat up pretty significantly. Ac cable with the strip apparently does not do this. Is that not the case?

New to this, trying to understand what's correct and what's safe
Originally Posted by Nashkat1
You can have a pro load-test the wiring for that if you want to.
 
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Old 09-14-13, 05:19 AM
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That sounds like a bond conductor. It can be wrapped in the spiral or cut off.

I have seen the spiral sheath glowing red from a short that was touching then metal without a bond strip. The spiral is multiple times longer than the actual cable length.
 
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