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Posted by Jeffrey Lebowski on February 24, 2007, 10:50 am
>
> > I'm replacing an old heat pump installation which had the thermostat
> > wiring and the 220V romex all within the same plastic conduit whip
> > going from disconnect to the condenser unit.
>
> If you were a *competent*, licensed, insured, professionaly trained, HVAC
> technician, you would already know the answers to your questions.
> The answers you seek are in the NEC, and I believe also in the UMC
> Maybe you should check with you local building inspectors?? You *did* pull
a
> permit, didn't you??
> I will however give you some answers below...keep in mind that these
answers
> are based on the requirements in my location.
>
> > I understand thisn't acceptable per current code. I need a couple
> > clarifications.
> >
> > 1. Can std. Romex wire be used in a conduit or does it need to be
> > individual wires? (ie THHN)
>
> Romex won't pass inspection here.... use properly sized THHN
>
> > 2. It appears that thermostat wiring is permitted within a conduit if
> > it's insulation is rated for the same voltage as the high voltage
> > circuit. (ie CL1 220V).
>
> Not allowed here at all
>
> >However can std. thermostat wire (ie 18/4)
> > be contained in it's own small conduit within the main conduit??
>
> If its a heat pump, you will probably have more than 4 wires. Control
wires
> should be in their own seperate conduit, period.
>
If class 2 or class 3 power source is used then no raceway is required.
See nec article 725
Anyways, standard practice at least in my area is to route thermostat wire
along with the copper lineset between the condensor and ahu--the outer pvc
jacket holds up just fine under outdoors weather condition.
--
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