MC cable touching metal sprinkler pipes

[Rick N.]

I am currently an electrical inspector in VA, before that I was a commercial electrician. When I was in the field, I was always told that our MC cables couldn't make any contact with the sprinkler pipes, both metallic and non metallic. Now that I am on the flip side and performing these inspections I have been letting the electricians know that they can't have their cables come in contact with the sprinkler pipes. I cannot find anywhere in the NEC that specifically states that the cables cannot touch these pipes. Where would if any could I find a code article to enforce this?

 

[infinity]

There is nothing in the NEC that would require the separation you speak of. IMO it's a non-issue.

Welcome to the Forum.

 

[ptonsparky]

Now, do you apologize to those deserving, or just drop the issue?

 

[Rock86]

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[gadfly56]

I am currently an electrical inspector in VA, before that I was a commercial electrician. When I was in the field, I was always told that our MC cables couldn't make any contact with the sprinkler pipes, both metallic and non metallic. Now that I am on the flip side and performing these inspections I have been letting the electricians know that they can't have their cables come in contact with the sprinkler pipes. I cannot find anywhere in the NEC that specifically states that the cables cannot touch these pipes. Where would if any could I find a code article to enforce this?

If by "touch", you mean incidental contact it's not a big deal, although it should be corrected if found. If you mean strapped to or laying on, that's a no-no, and it comes from NFPA 13.

 

[curt swartz]

Metal is a non issue. The CPVC (orange pipe) apparently will disintegrate if anything come into contact with it. The pipe manufactures state in the instructions that basically nothing can come into contact with the pipe.

Recently on a number of jobs the fire sprinkler contractors have been posting notices from the manufacture stating that no plumbing or electrical cable can contact the pipe. Fire inspectors will frequently call it during inspection to. This is not an NEC issue but a pipe manufacture issue.

 

[gadfly56]

Metal is a non issue. The CPVC (orange pipe) apparently will disintegrate if anything come into contact with it. The pipe manufactures state in the instructions that basically nothing can come into contact with the pipe.

Recently on a number of jobs the fire sprinkler contractors have been posting notices from the manufacture stating that no plumbing or electrical cable can contact the pipe. Fire inspectors will frequently call it during inspection to. This is not an NEC issue but a pipe manufacture issue.

The manufacturer is probably just reiterating the requirements of NFPA 13.

 

[brantmacga]

It’s usually a specification on the projects I do that any conduit or cabling cannot touch metallic water lines, with a line that says “to prevent galvanic corrosion.”


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[102 Inspector]

As an inspector, I make sure that the sprinkler system is not being used to support the cable, but touching has never been an issue.

 

[infinity]

As an inspector, I make sure that the sprinkler system is not being used to support the cable, but touching has never been an issue.

I agree, incidental contact won't cause any harm unless you had a dissimilar metal issue which you would not with MC cable and steel sprinkler piping.

 

[jusme123]

NFPA 25, Standard for Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, National Fire Protection Association. Section 2-2.2 states,“Sprinkler piping shall not be subjected to external loads by materials either resting on the pipe or hung from the pipe.”

 

[infinity]

I see two different issues in this thread, resting on the sprinkler pipe and touching the pipe. The OP mentions touching the pipe, If the pipe is above the cables and they're touching the pipe there is no issue. I agree that other codes like the ones mentioned here would prohibit the pipe from supporting the cables.

 

[Fred B]

Stupid question here, what if there was an incident where the sheath of the mc was to become energized by a short, would that then translate to the sprinkler pipe system, and shock factor for anyone in contact with the sprinkler system? Would that be a plausible reason to restrict incidental contact between the 2 systems?

 

[ptonsparky]

Stupid question here, what if there was an incident where the sheath of the mc was to become energized by a short, would that then translate to the sprinkler pipe system, and shock factor for anyone in contact with the sprinkler system? Would that be a plausible reason to restrict incidental contact between the 2 systems?

Hopefully someone has paid attention to proper overcurrent and short circuit protection.
IMO it should be no different than laying against any other piping system. That and the sprinkler system is usually many feet above casual contact by anyone. It would be very far down on my worry list.

 

[suemarkp]

What does touching mean? If you run a strut rack and clamp sprinklers, EMT, MC, and anything else to that piece of strut to support each pipe or cable, they are in electrical contact (so galvanic or faults are all inter connected). I don't see an issue with that. But supporting cables or pipe off another pipe would be bad from a mechanical point of view. I could also see if the MC cable is touching a metal pipe, but not secured to it, it could possibly maybe erode the pipe if that pipe is expanding and contracting and rubbing a steel jacketed MC cable. But wouldn't expect that if the cable is flexible as I would think it would just ride the pipe as it moved as steel pipe won't be changing length that much. I could see a PVC pipe getting eroded in this case, especially one with hot water in it.

 

[mopowr steve]

I agree, incidental contact won't cause any harm unless you had a dissimilar metal issue which you would not with MC cable and steel sprinkler piping.

But that’s the rub, MC cable is an aluminum jacket resting against a steel/iron pipe.

 

[ptonsparky]

But that’s the rub, MC cable is an aluminum jacket resting against a steel/iron pipe.

Which one will rob or corrode away first? Any guesses?

 

[mopowr steve]

Aluminum.
At least is sure deteriorates quickly when against limestone foundations.

 

[infinity]

But that’s the rub, MC cable is an aluminum jacket resting against a steel/iron pipe.

That's not an issue. MC cable is run through metal steel studs, supported with metal straps and connect to steel boxes.

 

[EJPHI]

I believe the corrosion problem between dissimilar metals happens because of moisture and any DC potential. Since we deal with AC most of the time one could say that contact doesn't matter. You could also argue that all metal pipes and raceways should be bonded and therefore have the same potential.

Two other aspects: Raceway to pipe contact can be a problem with lightning induced ground current if you live in Minnesota, Florida, or other such place. You can get big enough arcs between systems to puncture L copper!!

A copper hot water pipe in contact with a steel conduit will form a thermocouple.....

I would vote for keeping them separated unless you can bond then together really well and avoid the two aspects mentioned above.

BTW FMC can be Steel or Aluminum.

EJPHI