Routing MC cable alongside a water pipe.

[Jon456]

I am installing a hot water recirculation pump in a commercial space and need to include a remote thermostat to control the pump. The thermostat is to monitor the temperature at the farthest hot water fixture; it turns on the pump when the water cools at that fixture and turns off the pump when the water at the fixture is hot again.

I believe it is acceptable to route the MC cable (controlling 120VAC power from the thermostat to the pump) alongside the water piping that returns the recirculation water from the remote fixture to the recirculation pump. The piping is 1/2" PEX enclosed in foam pipe insulation and will be suspended above the grid ceiling by hangers spaced at 32" intervals. I intend to zip-tie the MC cable to the outside of the pipe insulation and run it through the same hangers supporting the pipe.

Is there anything in the NEC that prohibits such an installation? Or are there other reasons why this would be a poor choice for the installation?

 

[sparky1118]

So you want to zip tie the mc to the water pipe?


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[Jon456]

So you want to zip tie the mc to the water pipe?

Yes. To the outside of the foam-insulated PEX pipe.

 

[sparky1118]

I don’t have my code book handy however I believe that is a no no. I don’t think you’re allowed to use a plumbing pipe as support. I could be mistaken


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[Jon456]

I don’t have my code book handy however I believe that is a no no. I don’t think you’re allowed to use a plumbing pipe as support. I could be mistaken

Technically, I'm using the pipe hangers as cable support. The reason for attaching the MC to the pipe with zip ties is simply to make for a neater installation.

 

[ActionDave]

The vertical rods that hold the hangers would be part of the structure so that would be alright to strap to. I wouldn't go through the hangers in case anyone needed to work on the pipe.

 

[Jon456]

I wouldn't go through the hangers in case anyone needed to work on the pipe.

The pipe I'm referring to will be a continuous length of 1/2" PEX from the copper pipe at the fixture back to the copper pipe at the recirculation pump. Other than the connection at the origin and the connection at the termination, there will be no joints in the PEX. There should never be any need to work on or otherwise modify this PEX pipe as its sole purpose is to return the recirculation water from the farthest fixture to the recirculation pump.

 

[Barbqranch]

Can you instead just measure the temperature of the water returning to the tank. It will run a little longer, but you will save all the wire cost.

That is what I did in my house.

 

[Jon456]

I could. However, it would cause the pump to run longer and more frequently.

But your point deserves consideration: which is more energy efficient in the long run? Saving the parasitic energy losses from the additional hot water in the return piping? Or saving the energy (and materials) used to manufacture the MC cable used to extend the thermostat to the farthest fixture?

 

[hbiss]

I've done that with LV thermostat wire and a Honeywell relay back at the circulator end. Doesn't change anything though. You can't strap that to the plumbing either.

-Hal

 

[texie]

Where in the NEC is what the OP wants to do prohibited?

 

[LarryFine]

NEC prohibits hanging stuff from conduit, but I believe it's up to the plumbing code to prohibit this.

 

[texie]

NEC prohibits hanging stuff from conduit, but I believe it's up to the plumbing code to prohibit this.

Exactly my point.

 

[Knuckle Dragger]

I have to admit.
I have ty wrapped a few armored cable in my years to gas/ water around boilers.
I try not to do it or over do it when ever possible.
Sometimes that way is most practical.

 

[Eddie702]

You can strap thermostat wire to a conduit containing line voltage going to a furnace or boiler and that is an exception only allowed because it is related equipment.

Don't think strapping to a hydronic pipe or plumbing pipe is a good idea. In this case the heat would be harmful to the wire.

 

[Jon456]

I need to reiterate that I do NOT intend to hang (or otherwise support) the MC cable from the water pipe. The MC cable will be routed alongside the water pipe and will be supported by the suspension hangers that are also supporting the water pipe. The reason for the proposed zip ties is simply for neat workmanship. For the sake of this discussion, let's just omit the zip ties and say that the MC cable is following a parallel path with the water pipe.

The heat from the water pipe will in no way affect the THHN conductors inside the MC cable. The returning recirculation water will be less than 115°F and the 1/2" PEX pipe will be enclosed in foam insulation with a 1" wall thickness (the outside diameter of the insulation is 2-5/8"). The MC cable will essentially be at the room's ambient temperature.

 

[hbiss]

I need to reiterate that I do NOT intend to hang (or otherwise support) the MC cable from the water pipe. The MC cable will be routed alongside the water pipe and will be supported by the suspension hangers that are also supporting the water pipe. The reason for the proposed zip ties is simply for neat workmanship. For the sake of this discussion, let's just omit the zip ties and say that the MC cable is following a parallel path with the water pipe.

For the sake of this discussion, you may consider the reason for Ty-rapping the cable to the pipe and insulation is for neat workmanship. But I can tell you that as soon as you do that the pipe is supporting the cable, no matter how you try to justify it.

Ok, so now no Ty-raps and I get that you want to thread the cable through the hangers that also support the pipe. I don't know. To me either way is lazy. I'm not seeing anything against it in the NEC but like was said, there are other codes that may apply. It's all too easy to hang cables off plumbing and duct work and if it was allowed you would see it done. I was always taught not to do that kind of thing.

-Hal

 

[Jon456]

There is a difference between support and secure. Even the NEC acknowledges that distinction. But I don't want to sidetrack this thread on the issue of the zip ties.

How is it lazy to have the MC cable follow the pipe? Does it make really make more sense to add a parallel set of suspension hangers (in an already severely cluttered overhead space) just for a single 14/2 MC cable that is going exactly where the water pipe is going? What does that accomplish in terms of functionality, safety, or ease of maintenance? Seems to me like a complete waste of materials, time, space, and money. More importantly, is it a code violation? That's what I'm trying to determine here.

Of course I could route the MC all the way up to the roof and thread it through the roof trusses along with the pre-existing tangled mess of MC cables for other branch circuits. But to me, that's more lazy and a lot less professional. And good luck to the poor sod who has to sort out and trace that jumble in the future.

 

[LarryFine]

I think the right installation would be to support the MC from the hanger rods outside the pipe hangers' loops.

 

[hbiss]

I think the right installation would be to support the MC from the hanger rods outside the pipe hangers' loops.

I was going to say the same thing. Why can't you ty-rap the cable to the hanger rods above the pipe?

-Hal