Electrical – NM cable next to hot water pipe


Edit: The answer below indicates that at least in some places inspectors consider it inacceptable to attach any wiring to pipes. However, I would still like to understand why it is a bad idea.

Original question: I had a gas boiler for the radiator hot water system installed. After the contractor left, I noticed that they ran two 12/2 NM cables from the boiler to the two pumps along the hot water pipe, attaching the cables to the pipe with plastic cable ties. I am concerned about the exposure of cables to the heat.

My questions:

  1. Is this installation allowable?
  2. If it is technically allowable, should I still be concerned?

Data: The two pumps are 0.75 and 0.81 amps respectively. The maximum allowable boiler temperature is 210F (but we won't ever run it that high of course, ours is set to 130F-180F depending on the outdoor temp).

According to my reading of 110.11 of NEC, it appears to be disallowed. On the other hand, according to the formula in 310.15(B)(2), using temperature of 180F it appears to be OK with a margin to spare. The 310.15(B)(3) does not apply since there are only two cables run together.

Best Answer

The heat with such a miniscule load is not really an issue. I wouldn't worry so much about the temperature as I would about using NM cable to wire pumps (I assume circulators?), and securing them to water pipes (which is not allowed). A much more professional job would have been to use MC cable and secure them to the boiler housing or simply tie wrapping them together.