Is there an electrical code for thermostat wiring? I know that there's
typically 24 VAC across the wires at probably a very small current level,
perhaps much less than half an amp.
I'm considering moving a thermostat and was considering using either
solid or stranded 18 gauge wire. Its for a simple hot water baseboard
radiator system, no HVAC.
Go to Home Depot or equivalent and buy some "thermostat" cable. Choose
between two, three or five wires based on what you now have or your
thermostat needs. If you have to join cables you can wirenut the wires
together (add some tape to prevent any accidental contact loosening the
wirenuts). They don't need to be in a box.
For hot water heat only, the fellow is likely going to use 18-2, which is
red and white.
I also use wirenuts and then tape when something might come loose. And when
I'm doing heating, I often wear belt and suspenders.
Christopher A. Young
Jesus: The Reason for the Season
The NEC most certainly does regulate low voltage wiring. Thermostat,
telephone, TV, cable TV, Cat 5 (etc.), sound circuits, door bell, intercom,
low voltage lighting controls, and more, even landscape wiring is covered by
Thermostat wiring is usually Class 2, which is addressed by NEC Article
725. Probably the biggest concern is that the low voltage cables be
installed and terminations made such that they will not be (accidentally)
energized by higher voltage circuits.
They should also be protected from nail and screw penetration.
The NEC does address low voltage wiring but no area I'm aware of
inspects so it is of no effect. Remember that electricians are a guild
and would like to prevent anyone not a member to be prohibited from
I'm ducking now, having made a poignant observation.
John Hines wrote:
Locally, it is inspected and required to be permitted. Most of the
code is related to not connecting low voltage to any standard wiring,
and that's what the inspector's are looking at for the most part.
Commercially, they get very concerned about fire wall penetration, as
they do in multi-family residential. The other thing they are looking
at locally now is grounding, especially concerning low voltage
lighting and voice/data/entertainment with external connections.
But that's local issues. We have a very high percentage of new and
remodel construction that involves extensive low voltage for
entertainment, alarms, lighting, data/voice and so on, so that's one
reason it shows up on the inspector's radar here.
I suspect the real reason it shoes up on the inspector's radar is that
they are worried about the "brotherhood" loosing out if too much moves
to low voltage control. They will next want to inspect optical signal
May the Guilds be perpetuated.
Thankfully, I'm in an unincorporated area that doesn't inspect anything.
Jeff Cochran wrote:
I'll also point out that the NEC rules are not only safety related, but
_also_ help improve the resulting system for the homeowner's benefit.
NEC/CEC rules talk about keeping separation (between power and LV) more than
1' and crossing at right angles "as much as possible".
Why? Well, of course, there's a paranoid safety element in there. But
following those rules also helps reduce hum and crosstalk in cable TV,
antennas, telephones, hi fi systems etc.
So, whether you care about the safety-nazi bit or the union bit or not,
following those rules as much as you can _is_ to your benefit in a better
quality installation and less electrical noise.
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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