Cat 6 as thermostat wire

[Jennifer Eden]

Hi,

Can Cat 6 wire (not sure of solid or stranded) be used as thermostat wire? I have 1000ft of the former and none of the latter!

Thanks in advance.

[RBM]

Typical heating/ cooling systems require 18 gauge, cat5 is 24, making it too small for the requirement, which is not to say that it won't work, especially if it's a short run.

[gfretwell]

If the run is pretty short it should work but real thermostat wire is cheap. Why add another level of confusion (different color code)

[LSMFT]

Yes.

[Jeff Thies]

I'm thinking the current requirements of modern thermostats/furnaces is pretty low.

Rates 24 at .57A for power transmission. That would seem to be plenty. Most volt ohm meters have a current scale, if the OP wishes to check.

I suppose you could wire the 4 pairs in cat 6 in parallel which would give the same capacity, that would seem unlikely to be needed, but I know little about thermostats.

Jeff

[Reed]

Thermostat wire is normally 18 gauge, Cat 6 is 22 or 24. (The smaller the number, the larger the conductor.) So you might want to pair up 2 conductors of the Cat 6 for 1 "wire" of the thermostat. Especially if it is a fairly long run from T-stat to furnace.

[RBM]

It all depends upon what the thermostat is controlling. Lots of equipment use tiny solid state relays and ice cube relays that don't draw much, but some systems use zone valves of various types and quantities, which draw more. 18 gauge is probably a safe bet for almost everything, which is probably why HVAC systems typically call for it. There is also the color coding as gfretwell mentions. It's just a lot cleaner and easier to use standardized colors

[Hugh Jassolle]

24 gauge should have a resistance of 25 ohms per 1000 meet. Considering standard loads and voltages for a thermostat loop with #24 you could end up with a 10 -15% voltage drop over all. That might not be enough to effect a simple circuit but it would be better to pair up the wires.

[Eric in North TX]

At the risk of getting slapped around, i always use sprinkler wire, it is 18ga and 1/2 the price of thermostat wire, usually 5 conductor or more (handy for heat pumps and remote sensors), and direct bury-able for what that is worth.

[Stormin Mormon]

It's good to use what's designed for the usage. That way, the next people who work on the system will be less confused. "Hey, bub... isn't that phone wire? What's that doing inside a furnace?" "Dunno. Lets rip it out."

[aemeijers]

On this, at least, we agree. Avoid doing things in non-standard ways, but if/when you have to, leave notes for the next guy. Either yourself in five years when you won't remember what the heck you did, or some poor tradesman in 20 years after your heirs start fixing the place up to sell it off.

[Jeff Thies]

Makes sense to me. :-)

Jeff

[hallerb]

saves questions by home inspectors too..........

[trader4]

And I believe that is likely a violation of the NEC. They have requirements for low voltage wiring too. And I would believe that the prohibition against paralleling conductors would apply there as well. Perhaps someone knows for sure.

Overall, given the low cost of thermostat wire, using it for a thermostat is a bad idea for all the reasons already given.

[Mark M]

The overall savings, in terms of absolute dollars is small. Stay with what's standard and give the next guy working on it a break.

Mark

[Stormin Mormon]

I've also found to avoid the absence of not using double negatives to contradict the refutation that previously rescinded the cancellation which had previously but not at present been issued to disregard the information which had been revoked.

Yeah, I'm funning with you. Once in a while I see a double negative like "avoiding non". Just gets me to thinking that it's often easier to write in positive voice. Sometimes I've no clue why the standard is this or that way. And some times I do things in the usual way. But, not always....

[trader4]

And that is a violation of the NEC for sure. Thermostat and similar low voltage cable used inside a house has to be at least CL rated and I've yet to see sprinkler wire that meets that rating.

[EXT]

Cat 6 is an expensive wire to use, but if you have it, you could use it depending on what you are operating. If you only need 2 wires for a simple heat only thermostat or possibly an air conditioning thermostat you could double or triple up the wires. If you are running a heating/cooling system with fan controls you need a 5 wire cable. Cat 6 may not be able to handle the load because the fan and system switching on the thermostat operate relays and may cause a voltage drop causing the relays to not stay closed or open whichever state they should be in.

Failing to provide enough information about what you are using it for, makes the accuracy of the answer questionable.

[trader4]

And I think that would likely be a violation of the NEC, which only allows doing that under a few special conditons.

Thermostat wire is inexpensive. Why anybody would want to screw around, is beyond me. Put the Cat 6 on Ebay and buy some thermostat wire.