Grounding Electrode Conductors

[Smart $]

The only way you can not have a metal water pipe electrode, with one already in existence, is to disconnect it or "unmake" it an NEC qualified grounding electrode (GoldDigger suggested one method). The problem is, with the NEC adopted by and into law, to do so would be performing an illegal act. The way I see it, the only way you can do it legally is to get an approved deviation from your AHJ... so get your AHJ involved.

 

[kwired]

Thanks everyone for your responses... Sorry for coming back late, was at a meeting all day. In the meantime, I did call back the manufacturer to confirm if the cold water pipe connection affected the machine or vice versa just to make sure.... He said again that it's the machine that gets affected. When I asked for an explanation unfortunately, he wasn't sure how, it's just what he's told by his engineers.

golddigger asked if the vendor asked for a separate earth electrode to the machine... The answer is no. All they say is we can't be connected to the cold water pipe.

so say I use an isolation transformer with an isolated ground going to the machine. Would this alleviate the problem? (If there is one). But I would still have to ground the secondary of the transformer to building steel... Wouldn't building steel be bonded to the cold water pipe anyway, in which case I'm back to square one?

Does this machine have a connection to water supply?

All other grounding electrodes should have similar effect on the machine. The equipment grounding conductor should have similar effect also. Their engineer needs to go back to theory class. If there is a problem of some sort he needs to be able to describe it much better.

 

[Fnewman]

I think the vendor has it backwards. They are worried that their machine will cause electrolysis in the water pipe. They should ground the machine with an isolated ground, this is not a questionable practice like the previous poster mentioned. It's questionable on today's computers, not equipment like this because it protects the rest of the building from this stray DC voltage that is known to exist on the ground. (electrolysis is performed with DC current into water)

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I agree - they have it backwards. I am aware of a situation in a home where the bond to the copper piping system was accidentally omitted. Over time, some thin wall copper tubing, furnished by a toilet vendor, developed pinhole leaks. A call to the manufacturer for replacement tubing revealed the solution (they apparently had seen it before). Bond added - problem solved, but not sure I completely understand the theory.

 

[gray.one]

Press the manufacturer harder. They should be able to explain themselves and not just blow you off.

I'm trying to think of how electrolysis could occur. Not seeing it.


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[gray.one]

Electrolysis happens when the metal of the pipe is in contact with the minerals, etc. in the earth surrounding the building.
It can cause currents to flow and an offset in the voltage of the pipe compared to the natural earth voltage.

I think you are describing an electrolytic reaction, not electrolysis. Electrolysis is the breaking of water into hydrogen and oxygen.


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[gray.one]

The first two paragraphs were a quote from golddigger.


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[Saturn_Europa]

I think you are describing an electrolytic reaction, not electrolysis. Electrolysis is the breaking of water into hydrogen and oxygen.

You are both right electrolysis can cause many chemical reactions and is used in many manufacturing processes. But in this case I think Golddigger was closer to the target. Reading from the conversation it sounds like the manufacture is concerned about galvanic corrosion caused by electrolysis. In which ions are stripped from the least Noble metal and deposited on the most. In this case it seems the manufacture is worried about their machine being the sacrificial anode. And the metal water line the cathode.

 

[gray.one]

You are both right electrolysis can cause many chemical reactions and is used in many manufacturing processes. But in this case I think Golddigger was closer to the target. Reading from the conversation it sounds like the manufacture is concerned about galvanic corrosion caused by electrolysis. In which ions are stripped from the least Noble metal and deposited on the most. In this case it seems the manufacture is worried about their machine being the sacrificial anode. And the metal water line the cathode.

From Wikipedia "In chemistry and manufacturing, electrolysis is a technique that uses a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction"

The dissimilar metals reaction is spontaneous. You don't have to force it to happen.

I stand by the wording, but what you and golddigger interpreted it as makes more sense.


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[Grouch]

Press the manufacturer harder. They should be able to explain themselves and not just blow you off.

I'm trying to think of how electrolysis could occur. Not seeing it.


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I think i will have to do that... call them up again and push for more information. What strikes me as odd also is that the hospital where this machine is being installed already has other similar machines. So this new machine is the latest and greatest... yet it's handicapped over this one issue? But the other, older models don't have this issue.

 

[Ponchik]

Use non metallic connection for the water to the machine

Why go through the bonding and un-bonding when Dennis suggested a great solution.

Just suggest the isolation of the machine with a plastic pipe. The machine is already connected to the grounding system via the EGC.

 

[iwire]

They should ground the machine with an isolated ground, this is not a questionable practice like the previous poster mentioned. It's questionable on today's computers, not equipment like this because it protects the rest of the building from this stray DC voltage that is known to exist on the ground. (electrolysis is performed with DC current into water)

There is no such thing as a truly isolated ground, they all have to tie together at some point.

If you had a truly isolated ground that would be a dangerous situation and one that is prohibited regardless of the type of equipment.

 

[gray.one]

Why go through the bonding and un-bonding when Dennis suggested a great solution.

Just suggest the isolation of the machine with a plastic pipe. The machine is already connected to the grounding system via the EGC.

I thought it was a great idea at first, but the water itself would complete the circuit. Ions flow though the water between dissimilar metals.


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[Saturn_Europa]

I think i will have to do that... call them up again and push for more information. What strikes me as odd also is that the hospital where this machine is being installed already has other similar machines. So this new machine is the latest and greatest... yet it's handicapped over this one issue? But the other, older models don't have this issue.

Honestly........it sounds like some of their engineers need to work themselves out of the book. As others have stated it sounds like total BS and that they are trying to solve a theoretical problem.


Post back what you find out/end up doing.

 

[310 BLAZE IT]

Does water also flow through this machine?

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[kwired]

I agree - they have it backwards. I am aware of a situation in a home where the bond to the copper piping system was accidentally omitted. Over time, some thin wall copper tubing, furnished by a toilet vendor, developed pinhole leaks. A call to the manufacturer for replacement tubing revealed the solution (they apparently had seen it before). Bond added - problem solved, but not sure I completely understand the theory.

Using wrong support straps or just mounting on certain surfaces can cause galvanic corrosion on a copper tube whether the tube is grounded or not.

 

[roger]

The bottom line is they are asking for a code violation and the AHJ's over the hospitals I have worked at would tell them to fix their problem because the electrical wiring will in fact be installed to applicable codes.

With that said, I doubt there's a problem at anyways.

Roger

 

[Ponchik]

I thought it was a great idea at first, but the water itself would complete the circuit. Ions flow though the water between dissimilar metals.


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Then I guess disconnecting the main water pipe as the grounding electrode will not get them anywhere.

 

[ggunn]

Thanks everyone for your responses... Sorry for coming back late, was at a meeting all day. In the meantime, I did call back the manufacturer to confirm if the cold water pipe connection affected the machine or vice versa just to make sure.... He said again that it's the machine that gets affected. When I asked for an explanation unfortunately, he wasn't sure how, it's just what he's told by his engineers.

My next move would be to talk to his engineer(s). It's quite possible he misunderstood something that they told him.

 

[roger]

My next move would be to talk to his engineer(s). It's quite possible he misunderstood something that they told him.

It is possible but considering this comes from a medical equipment manufacturer he probably heard them correctly. We had one manufacturer that told us we could not ground their equipment, of course we told them too bad and installed them per code then tested the room per NFPA 99 equipotential requirements. When they would come back to commission their machines and would lift all the EGC connections, claimed it caused a multitude of problems. When the local authority found out they shut the machine down and had the manufacturers installers schedule to have all their other equipment shut down so they could inspect each and every one regardless of the machines function, MRI, Cat Scan, Cath Lab, etc...

After that they got on board and believe it or not, they didn't have any problems.

Roger

 

[Dennis Alwon]

I remember 30+ years ago when the McDonalds around here got the first computerized cash registers they wanted us to drive a ground rod under the counters and disconnect the equipment grounding conductor. LOL No way sir....... As an aside, my boss fixed those machine. He stupidly hooked them to the high leg-- didn't think to check...Boom bye bye cash registers.