I'm running led strip lighting, on a hallway floor, for accent lighting. The floors are Warmboard subfloors, which house radient pex tube.

Here is the Problem:

When running the 18 awg cl2 wire, the wire comes up 1/2' away from the pex tube. The water in the pex tube can get as hot as 140 - 180 deg Fahrenheit.

Top View Bottom and Joist View


  • Is there a concern of running this 18 awg cl2 wire so close to the pex tube?
  • If it is a concern, is there any protective jacket, one that can be applied to the wire, to protect it from the heat?
  • 1
    Most house wiring is only rated for 75C (167F) the insulation can get soft and the wires shorting out would be my concern.
    – Ed Beal
    Commented Aug 4, 2016 at 21:32
  • How much current are you running through this? Commented Aug 4, 2016 at 22:26
  • Also, what voltage do these LED strips run at? Commented Aug 4, 2016 at 22:39
  • @ThreePhaseEel The LED strips will be run at 12v and around 3amps. Commented Aug 5, 2016 at 0:10

2 Answers 2


You will have to rewire the circuit with a cable rated at 90°C -- type CL2 cables not further marked are only good up to 60°C, as per note 15 to the tables in the UL Wire/Cable app guide.

As to wire gauge -- 18AWG 90°C wire is rated for an ampacity of 14A by the NEC (table 310.15(B)(16)), and the maximum derate factor required for the OP's operating conditions (max 82°C) is .29 from table 310.15(B)(2)(a) -- this means you can only push 4.06A through the cable without exceeding the insulation temperature ratings or upsizing it. 14AWG should be more than ample, even at such a harsh derate -- 14AWG 90°C; wire can handle a whopping 25A, and since you are derating, you don't have to worry about the terminations being limited to 75°C. A 14AWG 90°C cable (even with the extra derate being imposed by the limitation to 60°C ampacities in the table by the use of NM or UF) can handle that same 4A with ease, and a 12AWG wire gets you 5.8A

  • The only issue with this is the wire size. If 14 AWG is used, then connecting then soldering the 14 AWG wire onto the LED strip leads is rather hard if not impossible. See pic: imgur.com/a/yCY32 @ThreePhaseEelWhat What is the best way to solder the 14 AWG wire to LED strips like these? Commented Aug 7, 2016 at 18:23
  • You can solder a "pigtail" of 18AWG fixture wire (TFFN) to the strips and then use wirenuts or push-in type connectors to connect them to the 14AWG wire run. Commented Aug 7, 2016 at 18:41
  • But it's against code to pigtail or use a push-in type connector outside of a junction box, correct? The pigtail or push-in type transition would have to be housed inside the LED aluminum channel. Commented Aug 7, 2016 at 21:47
  • @RyanLazuka -- actually -- use the 18/2 CL2 you have for the pigtails, that way they can run into a junction box where you can make the transition to 14AWG or what-have-you Commented Aug 7, 2016 at 23:22

Use wire rated for 90 degrees C, and use thicker wire than is necessary. That should be easy since you are using 18 AWG wire, and the wire I'm talking about is 14 or 12 AWG.

A lot of wire is rated for 90 degrees C, however you can't use the higher current rating at 90C because the wire terminations are only listed or 75C. That won't be a problem here.

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