I need to relocate a thermostat and have the additional wire needed but I am not sure of the ideal way to "join" the cable sections.

Will using wire nuts and zip tie be good enough?

  • 1
    One thing to be aware of is that most thermostats control the equipment with thin low-voltage wires (24V) which are not particularly dangerous, but some electric heat has line-level voltage going to the thermostat (normal electricity wires, 120V or 240V) which needs to be properly installed like any other live electric wire. – Hank Oct 2 '15 at 3:23

A butt splice connector, or twist-on wire connector would be fine. Just make sure you use connectors that are designed for the size, and number of wires being connected.

Butt splice connector
Twist-on wire connector

Technically, you should probably either pull all new wiring, so that it's continuous from HVAC to thermostat. Or put the connections in a junction box, that is left accessible.

  • ok, I'll use twist-on wire connector. Is there a code that tells in what height the thermostat need to be? – Grasper Oct 1 '15 at 18:39
  • @Grasper Not that I'm aware of. Check the manufacturer's documentation, they might recommend an installation height. – Tester101 Oct 1 '15 at 19:17
  • Are low voltage connections exempt from accessibility regulations, I.E.not burying the connections in a wall? – HerrBag Oct 1 '15 at 23:03
  • @HerrBag Not exactly. – Tester101 Oct 2 '15 at 2:07
  • @HerrBag To my knowledge, I don't think NEC covers 24 volt HVAC control wiring, but I could be wrong. If they do cover it, I've seen thousands of violations. I don't think I've ever seen 24 volt thermostat wiring terminated in an enclosure, nor have I seen 24 volt thermostats that would attach to standard size boxes. – Tester101 Oct 2 '15 at 2:15

DO NOT use a crimp connector on solid conductors.

NASA approves crimp connectors only on stranded wire, and specifically prohibits the use of crimp connectors on solid wire (see 4.3.4 on page 23 of the link below). Solid wire should be spliced by soldering; or in the building trade, wire nuts may be acceptable.


As with anything else, consider the consequence of primary failure (the thing doesn't function as intended), and secondary failure (house freezes because thermostat failed to call for heat, or fire from high resistance due to improper connection).

BETTER CHOICE for the DIY person is a new connector from Ideal which is approved by UL, made in USA, and available at Home Depot and Amazon ... Spliceline. More expensive than soldering and heatshrink, but easier and faster for sure; although a little bulkier.


  • Solder only connections are not allowed in the U.S.. A wire nut would be acceptable. – Ed Beal Nov 18 '16 at 13:53
  • Crimp connectors are not designed for solid wire. they don't bond well at all. I know this from experience (and so does NASA). – isherwood Nov 18 '16 at 14:06

Wire nuts or Butt Connectors work fine. I would ziptie or knot the ends together to prevent them from being pulled apart.

There is no issues with shorting. If the wires short your furnace will turn on. Thats all the thermostat does anyway.

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