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Our gas furnace, while quite functional, has some quirks in its installation. One of them is that the installers cut off the old (original to the house) thermostat wires at the ceiling above the furnace and open-spliced (with wire nuts) new thermostat wires to the old. While not all that neat and workmanlike, this is Code-legal for class 2 control wiring as far as I understand it. There is also one point where the wires are attached to the EMT feeding power to the furnace, which is covered by 300.11(B)(2) in the 2014 NEC.

More interestingly, though, the majority of the support for the new thermostat wire is provided not by the EMT for the furnace power, but by the black iron gas line feeding the furnace. Yes, that's right: the furnace installers neatly zip-tied the thermostat wire to the gas line at regular intervals. Is there anything in the 2006 IRC/IMC/IFGC, 2002 NFGC, or 2014 or 2017 NEC that prohibits this?

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    It's likely that the HVAC tech that did the installation has no knowledge whatsoever of the NEC, or any formal electrical training (outside of troubleshooting HVAC systems). It's also likely that if the installation was inspected at all, it was not inspected by an electrical inspector. That being said... I'm not sure there's anything in the NEC that would prohibit securing the cable to the pipe, as long as the pipe is properly secured and supported. – Tester101 Dec 12 '17 at 13:06
  • 300.11(C)(2) sort of fits. – Tester101 Dec 12 '17 at 13:15
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Yes it's okay and actually very very very very common. Even the armoured 14 2 cable can be strapped to the gas pipe. Here in Toronto we have the toughest codes around and that's the only way it's done. I'm a licensed gas fitter and electrician. It can't be NMD it has to be armored BX or Tek cable.

  • I take it this is one of those cases which is permitted by way of the Codes being silent on the topic? – ThreePhaseEel Feb 18 at 5:27
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    Yeah kind of a gray area. I'm not very familiar with electrical code but to my knowledge there's nothing in there that says it's bad. I'm primarily HVAC, full time 20 years and worked with Dad off and on throughout my childhood since about 7. Never had an issue with the wires running down the gas line in any way shape or form. – Joe Fala Feb 18 at 5:33
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Provided the cable is tough enough for the conditions and the pipe is earthed,if appropiate for your installation.I see no problem.INspector may disagree,how engineer is trained may cause disagreement.THe responsibility lies with the installer to ensure regulaions are followed.Steve uk engineer.

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