Electrician says corroded ground electrode needs replacing

[redikillowatt]

On a remodeling addon job, the electrical contractor says the single grounding electrode needs replacing because it has rust at the top where a brass acorn clamp is attached (rod is exposed above grade). It is rusted, but clamp looks good. He also wants to replace the short GEC from panel to driven rod.

Is it necessary to replace a ground electrode because it has rust? For grins, I cleaned a spot on the rod below the brass grounding clamp & shined a spot on outside of brass clamp a bit & also a spot on GEC ( above the ground clamp). Resistivity between clamp & rod, and the GEC (from above clamp) to rod - below clamp - then were each < 1 ohm. Seems to indicate conductivity between both GEC, brass clamp & rod are still good, in spite of corrosion.

Can't say about resistance between such rusty ground rods & earth in a high rainfall area like this. He didn't check that.
The rod & clamp above ground were dry at the time of testing, but it has rained w/in last week.

I've worked on hundreds of older homes w/ similar looking rods & electricians never give them a 2nd look. I wonder if inspectors would require replacing rusty, but otherwise solid driven ground rods or what the actual requirements are for deciding if a driven ground rod needs replacing?

 

[growler]

On a remodeling addon job, the electrical contractor says the single grounding electrode needs replacing because it has rust at the top where a brass acorn clamp is attached (rod is exposed above grade). It is rusted, but clamp looks good. He also wants to replace the short GEC from panel to driven rod.
I wonder if inspectors would require replacing rusty, but otherwise solid driven ground rods or what the actual requirements are for deciding if a driven ground rod needs replacing?

It's hard to say what a local inspection department will want. It normally depends on what you are doing as far as the remodeling job goes. You should have a permit and you will find out.

Here if you are doing any up-grading to the service they may require a second ground rod installed. Do you have a good cold water ground or is there PVC running in from the street? If you have a good cold water ground then made sure this is connected correctly. If these ground rods are all there is then a second ground rod may be required.

If you want to know what the inspector will want then call and ask him/her. That's the only way I know.

 

[redikillowatt]

Thanks Growler.

No work's being done on the service entrance on this job. Besides, this is in the county & there are no electrical inspectors here. Was just the electrician's recommendation to replace the ground rod. He didn't say he tested it & I didn't see him test it. Only explanation was "the ground rod is corroded" where the grounding clamp & GEC are attached.

Maybe my question should have been, unless a grounding electrode test is done, does corrosion on the driven 8 ft rod at the ground clamp, necessarily mean the rod needs replacing (when clamp & GEC still in good shape)?

If a ground rod test showed too high resistance, of course it'd need replacing or additional rods added. In this case & many houses in the area, plastic water line is used up to houses & (mostly copper) interior water lines don't run under the slab, so they're not reliable grounds.

My simple test of resistance between the GEC, clamp & rod showed they still had low resistance connections (despite corrosion present), but doesn't test resistance of ground rod to earth. One reason I ask is, I see ground rod corrosion on older homes frequently. It's typically smooth corrosion, not crusty. So far, never heard of anyone getting shocked. I assume many of these old rods were galvanized - possibly copper bonded - & the coating has corroded away. But they appear to still be working - at least no owners w/ rods like this have had any electrical problems.

 

[growler]

Maybe my question should have been, unless a grounding electrode test is done, does corrosion on the driven 8 ft rod at the ground clamp, necessarily mean the rod needs replacing (when clamp & GEC still in good shape)?

If the connection is still tight and in good shape I don't worry about it. This is all that was required at the time of installation.

Now if there is a reason for me to inspect and verify that the service is safe and up to code then a second ground rod is the easiest thing I can do to satisfy the local inspection department. Ground rods are not that expensive.

If there are any doubts about the connection I would use a wire buffing wheel that attaches to a cordless drill motor and clean up the connection. Make sure everything is tight.

As far as I know they all get corroded after awhile.

 

[roger]

Basically the grounding electrode (rod in this case) only comes into play for lighting events and HV surges and with this being the case, at the high voltages of either event the rod probably wouldn't see much difference in performance corroded or spotlessly clean. IMO there would be no need to change it. See 250.4(A)

To do a propper test you would need a three or four point fall of potential test set or a clamp type ground rod tester. The NEC only requires 25 ohms for a single rod, if you can't meet that (and you probably won't) you can simply drive one more rod and be done, there is no minimum for multiple rods.

Roger

 

[GUNNING]

Choices we are comfortable with

Choices we are comfortable with

If you don't want him to do it tell him no.

If there are signs of deterioration on the ground rod then why not replace it. If you live in an area with lightning spikes on the service it couldn't hurt, and maybe a surge protection device on the panel too. It will help to save that new flat screen TV.

Just because there is no resistance between clamp, ground rod, and GEC at 9 volts does not meant it will hold up under 50K volts of electrical surge from a lightning strike or a lost ground at the distribution transformer. Rust is a sign of failure. If the surface area was affected or flaking off then the overall area and strength of the ground rod might come into question. That is an engineering question. Pretty sharp of the electrician to check out the ground rod. Those Zinc ground rod clamps powder up and disappear leaving you with no ground rods attached to your service. In some parts of TX they use sulfuric acid to dissolve and extract uranium minerals underground. You would be surprised what sulfuric acid does to ground water. How much ground rod is left?

When you go into a pharmacy do you get mad at the pharmacist for suggesting a probiotic with the antibiotic or do you go for the laxative in 3 and a half weeks? It's a suggested sale to improve your quality of life not an insult. Maybe the electrician knows something you don't, ask him.

 

[redikillowatt]

I think you all make good points. Wasn't so much a case of me (or homeowner) not wanting him to replace the rod (now 2 are typically installed, unless using Ufer ground). Just wondering why it hasn't come up in the past. From my view, it's probably a good idea to replace rods w/ obvious corrosion. If not "required" by some authority, some homeowners need convincing.

FWIW, this ground clamp is bronze, not zinc. No idea if it's original or what coating was on electrode originally.

How much ground rod is left?

No way to know w/o digging or at least doing a rod resistance test. Probably easier to install new rods.

When installing 2 or more driven rods - 6 or 10 ft apart, etc. - does NEC require an unbroken GEC all the way from residential service entrance panel, to 1st rod & then on to others; or can the 2 (or more) rods be bonded w/ a separate conductor of correct size? If it must be unbroken, connecting all electrodes back to panel, maybe that's why he suggested replacing the GEC from the panel.

 

[Dennis Alwon]

Grounds rods are virtually worthless and they do have only a 20-30 year life span- so I have read- Replacing it is not necessary however depending on the age and the soil conditions it can't hurt. I would have added a cee in the footers of the additions before replacing the rods.

 

[Twoskinsoneman]

some homeowners need convincing.

Some electricians too...
It sounds like we're talking about a little surface corrosion and you'd have a very hard time convincing me there was any value replacing it. He's trying to make a little more money and that's ok I guess, but it is not needed.

 

[roger]

When installing 2 or more driven rods - 6 or 10 ft apart, etc. - does NEC require an unbroken GEC all the way from residential service entrance panel, to 1st rod & then on to others; or can the 2 (or more) rods be bonded w/ a separate conductor of correct size? If it must be unbroken, connecting all electrodes back to panel, maybe that's why he suggested replacing the GEC from the panel.

Roger

 

[redikillowatt]

Excellent diagram, Roger (& Mike). Obviously not an unbroken conductor between all those electrodes.

Although, I believe (could be wrong) NEC requires a bonding wire to be unbroken (not spliced, clamped, etc.) between any 2 electrodes - as in a rod is driven on opposite end of a house for an antenna & a continuous bonding wire run around (or thru) house to the service entrance ground, if the service ground (rod) is the only other ground electrode.

 

[kwired]

Some electricians too...
It sounds like we're talking about a little surface corrosion and you'd have a very hard time convincing me there was any value replacing it. He's trying to make a little more money and that's ok I guess, but it is not needed.

He should also suggest replacing all the rusty rebar in the CEE, this will give his GC friend more work to do and in turn more work for himself.:happyyes:

 

[George Stolz]

Although, I believe (could be wrong) NEC requires a bonding wire to be unbroken...

You are mistaken. 250.53(C).

 

[Twoskinsoneman]

He should also suggest replacing all the rusty rebar in the CEE, this will give his GC friend more work to do and in turn more work for himself.:happyyes:

I'm all for offering add-on's but this seems to border on shady...

 

[kwired]

I'm all for offering add-on's but this seems to border on shady...

But it is good for the economy. Creates jobs, sells products..., and the owner will be much safer when it is all done.

 

[redikillowatt]

You guys are a riot!

George - I can't find the full text of NEC 250.53(C), but I was speaking of requirement for a single bonding wire between any TWO electrodes to be unbroken. As in, if bonding 2 electrodes 100 ft apart, NOT being allowed to use (2) 50 ft pieces of wire - clamped, spliced, twisted together, in between those 2 electrodes. Is that correct?

Yes, I see all bonded electrodes in the system don't require one continuous wire between them.

 

[John120/240]

You guys are a riot!

George - I can't find the full text of NEC 250.53(C), but I was speaking of requirement for a single bonding wire between any TWO electrodes to be unbroken. As in, if bonding 2 electrodes 100 ft apart, NOT being allowed to use (2) 50 ft pieces of wire - clamped, spliced, twisted together, in between those 2 electrodes. Is that correct?

Yes, I see all bonded electrodes in the system don't require one continuous wire between them.

See 250-64.c allows you to splice the GEC with a exothermic method (cad weld) or use an

irreversible compression crimp.

 

[kwired]

See 250-64.c allows you to splice the GEC with a exothermic method (cad weld) or use an

irreversible compression crimp.

The irreversivle compression crimp must also be identified for grounding, can't be just any crimp connector.

 

[weressl]

Basically the grounding electrode (rod in this case) only comes into play for lighting events and HV surges and with this being the case, at the high voltages of either event the rod probably wouldn't see much difference in performance corroded or spotlessly clean. IMO there would be no need to change it. See 250.4(A)

To do a propper test you would need a three or four point fall of potential test set or a clamp type ground rod tester. The NEC only requires 25 ohms for a single rod, if you can't meet that (and you probably won't) you can simply drive one more rod and be done, there is no minimum for multiple rods.

Roger

Clamp-on, electrodeless tester is much quicker.

 

[weressl]

Grounds rods are virtually worthless and they do have only a 20-30 year life span- so I have read- Replacing it is not necessary however depending on the age and the soil conditions it can't hurt. I would have added a cee in the footers of the additions before replacing the rods.

Hmmm, they seem to hold up even in chemical plants past 50 years. On the other hand I have seen severely corroded reinforcement steel in wet concrete.