Thread: Bonding Question

I have 2 questions regarding bonding.

62 year old small single story house entirely plumbed with galvanized on the supply (that portion which is visible) and distribution side and cast iron on the drain/vent side. I can see all this plumbing from the nice dry well lighted basement or attic. There are no Fernco fittings breaking the metallic continuity. I can see both the galvanized supply side piping and the cast iron drain side piping exiting the basement slab and presumably buried tightly in earth all the way to the street at the water meter and sewer connect which is over 100 feet away.

1) Is it reasonable to assume these piping systems are well grounded and have the ability to safely discharge errant current to ground?

2) Is my understanding of bondings second function of aiding in the operation of OCPDs also accurate and regardless of the answer to #1 the water piping systems should still be bonded to the electrical systems grounding system.

I think the answers to both are yes...but want to confirm.

My apologies in advance to the more knowledgable amoung us if I've used incorrect terms for any system.

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1) No. There's always something you can't see. How do you know if the ground rod is the proper length or that there's not a plastic incoming water line outside the foundation? Your report is based upon what you observe, don't lead the client to believe more than that.

2) Technically, the system's grounding does not "aid" in the disconnect's function. The grounding of a circuit basically provides a second avenue for current to return to the panel. The grounding of the system allows for spikes such as lightening strikes to safely reach earth. Ideally, the system's grounding conductors carry no current, until there's a problem. The role of the neutral conductor on the SEC is to carry the imbalance of the two 120 lines back to the transformer.

Neutrals and grounds are different animals and it's not easy to pick up on their roles until you've heard it explained over and over and over again.

Originally Posted by Robert Foster

I have 2 questions regarding bonding.

62 year old small single story house entirely plumbed with galvanized on the supply (that portion which is visible) and distribution side and cast iron on the drain/vent side. I can see all this plumbing from the nice dry well lighted basement or attic. There are no Fernco fittings breaking the metallic continuity. I can see both the galvanized supply side piping and the cast iron drain side piping exiting the basement slab and presumably buried tightly in earth all the way to the street at the water meter and sewer connect which is over 100 feet away.

1) Is it reasonable to assume these piping systems are well grounded and have the ability to safely discharge errant current to ground?

2) Is my understanding of bondings second function of aiding in the operation of OCPDs also accurate and regardless of the answer to #1 the water piping systems should still be bonded to the electrical systems grounding system.

I think the answers to both are yes...but want to confirm.

My apologies in advance to the more knowledgable amoung us if I've used incorrect terms for any system.

You should never assume anything.... "ASS-U-ME"

If you do not see any bonding then you should simply note that you did not see any bonding device, wire, cable, etc, so you can not verify that the system is bonded. I have this little statement in all of my reports just to cover myself.

All plumbing systems that are metallic should have bonding. PEX, CPVC, PVC, PB do not require bonding, but I have known a couple AHJ's to require it.

1959 Un-upgraded electrical system, would not likely be a three-conductor wiring system, polarized receptacles perhaps, but not three-blade "grounded type" receptacles. In any event, cable and conduits popular at the time, are no longer used in the manner and form they were then, especially as to undersized or insufficient EGCs if present and undersized neutrals, or for their non-existant EGCs.

"floating grounds" to plumbing system are NOT sufficient or safe to provide EGC for "three blade" receptacles, etc. "floating grounds" might fool your three-light tester, but do NOT indicate the presence of a properly bonded system, nor continuity to the service bond to earth.

Bonding the service to the water pipe is not sufficient, there must be at least one other electrode. All other metallic system sections that may become energized must be bonded. The water pipes may not be used as branch circuit equipment grounding conductors.

Thanks for the replies.

I didn't mean to suggest I was going to include anything based on assumptions in my report. This question wasn't about report writing it was about increasing my knowledge and the particulars of yesterdays house got me thinking.

regarding...

1) perhaps it would of been clearer to say... assuming the specs stated in my first paragraph would it be reasonable to assume the water piping systems are sufficiently grounded to successfully conduct a transient over voltage event such as lightening back to ground.

2) I've read in one of my books that bonding, during certain component malfunctions, aids in the ability of over current protection devices to detect the malfunction and operate successfully. I don't understand this, but following up with more precision will have to wait till tomorrow cause I gotta go right now.

Originally Posted by Robert Foster

Thanks for the replies.

I didn't mean to suggest I was going to include anything based on assumptions in my report. This question wasn't about report writing it was about increasing my knowledge and the particulars of yesterdays house got me thinking.

regarding...

1) perhaps it would of been clearer to say... assuming the specs stated in my first paragraph would it be reasonable to assume the water piping systems are sufficiently grounded to successfully conduct a transient over voltage event such as lightening back to ground.

You should never assume anything about lightning. The intent of the ground path in electrical systems is to resolve the voltage potential between a conductor and earth. Bonding the water piping to the grounding conductor ensures that all metalwork is at the same potential with respect to earth to protect occupants from electric shock due to use or a fault. It is neither designed nor intended to be a lightning arresting system.

2) I've read in one of my books that bonding, during certain component malfunctions, aids in the ability of over current protection devices to detect the malfunction and operate successfully. I don't understand this, but following up with more precision will have to wait till tomorrow cause I gotta go right now.

While GFCI and combo AFCI devices measure voltage potential with respect to ground to detect current leakage, common circuit breakers do not measure ground potential. They typically are thermally and magnetically operated based on the amount of current passing through the device. Whether that current is discharged to ground via the neutral conductor or the bonding conductor shouldn't matter to their operation.