Thermostat/low volt wire that is CL2 and direct burial rated?

[trader4]

Here's the application. I have a solar pool controller located outside a single family house that puts out 24V which will go to a relay located in the attic. The controller is about 6 feet away from the house, so the circuit will go from the relay in the attic, down the outside of the house behind a pipe, but then needs to go underground for the last 6 feet to the pool controller. Besides the relay circuit, there will also be 4 other wires for sensors. So, I need a 20 gauge cable with 6 or 7 conductors.

I've searched high and low online and can't find any wire that will meet code. Everything that is CL2 or CL2X rated, eg thermostat cable is NOT rated for direct burial. And anything that is rated for direct burial, eg irrigation/sprinkler cable, is NOT rated CL2. Anyone know of any such cable that is 20 or 18 gauge? And am I right, per NEC 725 that I can't just use the sprinkler cable for the whole run?

What are my other options? I'm thinking I could mount a small weatherproof box on the side of the house near ground level and transition from CL2 to sprinkler wire for the last 6 feet underground. Or can I use the CL2 thermostat type wire and then put it inside PVC conduit for the underground run avoiding the splice? Is there a flexible PVC I could run, like is flextight allowed underground for low voltage?

This has to pass electrical inspection as other work is being done too.

And this got me thinking. All the irrigation installs I've seen just use irrigation cable that is not CL rated and yet they bring it inside garages, basements, etc. That would seem to be a technical violation of NEC 725, no? Do they just get away with it because it's a short run and/or there is no electrical inspection done?

[Twaynes]

Look into phone wiring; I don't know what it's called but they do have 24 Ga weather cable; not sure about buried for a cable with that few pairs, but might be something useful. Smallest I've noticed, IIRC, is 12 pair 24ga twisted for underground use.

HTH,

Twayne`

[jamesgangnc]

24 is a bit light for any distance/current.

[gfretwell]

If you have an open permit, call the building department. They will talk to you about it.

Anything that is wet location rated will be OK in a conduit underground tho. The easy way is to run a PVC raceway down the house, underground and up into the controller. You can use an LB on the outside wall with a nipple and a bushing on the "goes in the house" part.

[bud--]

I would want direct burial to be a lot tougher than any CL2 I have seen. Buried conduit should have wire that is wet rated. CL2 can be marked WET

- don't know if it actually exists. I would prefer something like #14 THHN/THWN in buried conduit and splice at the house.

CL cables are tested for flame spread and maybe smoke and fuel contribution to a fire. Didn't see where non-CL2 is allowed, but it doesn't make sense that conventional wiring is not allowed. The class 2 source limits the voltage, current and power (except in Twayne's world).

Never had anything to do with irrigation (lawn sprinklers?). Would think there wouldn't be much fire of smoke hazard from small amounts of the wire.

Sounds like the classical "ask the inspector". Their answers would be interesting.

[Dan Lanciani]

| I've searched high and low online and can't find any wire that will | meet code. Everything that is CL2 or CL2X rated, eg thermostat cable | is NOT rated for direct burial. And anything that is rated for | direct burial, eg irrigation/sprinkler cable, is NOT rated CL2.

Google Cable Substitution Chart. You can almost always use a variety of CM cable where you can use CL2, and CM cable is available with a wider range of characteristics.

Dan Lanciani ddl@danlan.*com

[trader4]

Thanks for all the input guys. I think I've figured out what to do. I'm going to use CL rated thermostat type cable in the attic from the relay over to a new small junction box located inside the attic by the eaves. Inside the box I'll transition from that CL cable to sprinkler cable that is underground rated. From there it will go directly outside, secured with cable ties to the back of a

2"PVC pipe, down to the ground, where it will get buried for the last 7 feet to the pool controller.

AFAIK from reading the codes, that should meet all the requirements. It turned out better from cable availability in reasonable lengths/ prices and also ultimately a single cable would have to go to 2 different locatons, so I can just split it off at the attic box.

The only remaining thing I'm left wondering about is how deep does it have to be underground? There is nothing in NEC 725 about it specific to Class 2 power limited circuits that I could find. Since it's only 7 ft, I guess I'll just make it 2ft and then I'll be OK for sure, but clearly they route similar sprinkler cable from controllers inside houses to underground and only bury them 6" or even less.

[Twaynes]

Duhh, it meets or exceeds what the OP said he wanted.

[bud--]

My reading of 725 is that it wants conventional wiring or CL or CM or maybe PTLC. Don't think sprinkler cable is one of them. But it seems entirely reasonable with the circuit having class 2 protection. (If the inspector doesn't agree, sprinkler cable would, of course, be entirely unreasonable.)

About 25 years ago, before the code came up with CL wiring, the class 2 source was considered to protect about anything (except in Twayne's world). Seems excessively restrictive now.

IMHO the consideration is system reliability.