I would like to order some wire online but don't know what it's called. Two-conductor shielded copper wire for 24V, insulated so it could be secured with zip-ties to the HX supply and return pipes running between the boiler and the indirect water heater. It connects to the aquastat. What's this kind of wire called?

  • We called it shielded 2 conductor wire ??? gauge or Shielded 2 conductor thermostat wire. The term depends a lot on where you purchase it. Be sure you pay attention to the temperature rating. If the insulation voltage rating is higher, great that is OK.
    – Gil
    Commented Sep 9, 2021 at 21:29
  • Are you in the U.S.? Can you please provide a pic with something familiar, like a penny or a pencil or a measuring tape in it for reference?
    – DAS
    Commented Sep 9, 2021 at 22:51
  • 1
    are you sure that it has to be shielded?
    – jsotola
    Commented Sep 10, 2021 at 0:02
  • @jsotola: Not at all sure, but I figured it couldn't hurt since these wires run under the stereo and speakers in the floor above; those speakers buzz now and then for no apparent reason.
    – mr blint
    Commented Sep 14, 2021 at 12:35

1 Answer 1


18/2 or 16/2 shielded CMR will do

One lesser-known thing about the NEC is that type CM (communications) cables with the correct wire gauge and count can be freely used for any application that calls for a type CL2 or CL3 (low voltage control) cable. So, I'd use a shielded two-conductor in-wall audio or security-alarm cable for this -- these are type CM(R), and many of them are of sufficient gauge to handle anything a thermostat cable can.

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