Basically, Installing a pump start relay into my system. Would like to run 6 #12AWG THHN wires through a carflex 1/2 conduit, from pump pressure switch, (under house, crawspace)area, up to 4"x4" carlon relay box, in garage. Two power sources (one from 220V CB), and other (set of 3 wires), from the pump pressure switch. 24V control comes from irrigation controller. My question is: Do the 6 THHN wires have to be held down with something like a cable tie, once inside of the relay box?, or can these just go straight to the relay terminals. thank you.

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    What are you using for a relay? Aug 14, 2021 at 19:52
  • Thank you for asking. I picked up a DPDT POWER RELAY 8 PIN 24VAC, through Grainger. the first relay that i picked up locally, did not meet the specks for my 1HP submersible pump.
    – bill
    Aug 15, 2021 at 21:35
  • I take it you want the irrigation controller to be able to trigger the pump even if the pressure switch isn't calling for water? Aug 15, 2021 at 23:34
  • My question is: Do the 6 THHN wires have to be held down with something like a cable tie, once inside of the relay box?, or can these just go straight to the relay terminals. thank you.
    – bill
    Aug 16, 2021 at 14:29
  • The RIBT24P brings its high voltage leads out using pigtails, so there's no need to faff about with any sort of cable-tie shenanigans Aug 17, 2021 at 1:08

2 Answers 2


You'll want a relay with high/low separation

Your primary problem is that you need (by Code) to separate the 24V irrigation wiring from your 240V mains wiring in a fashion that won't let some mishap put 240V on the 24V circuit, ruining your irrigation controller and potentially even starting things on fire. Furthermore, your relay needs to be fully UL listed (not just RU component recognized aka Rather Useless to us) for use at mains voltage, which leads us to one choice given the separation requirements, namely the Functional Devices RIBT24P. This provides us with a 24VAC coiled, UL listed DPDT enclosed relay capable of handling a 2HP 240V motor and fitted with an enclosure barrier to keep the 24V and 240V streams from crossing.

This relay then attaches to your relay box via its ½" nipple, and gets its NO contact(s) wired in parallel with the contacts on the pressure switch using some wirenuts, as the RIBT24P's high-voltage leads are brought out as pigtails in the box. The NC wires on the relay then get capped off by themselves, the low-voltage terminals get hooked up to the irrigation controller using a suitable low-voltage cable, and a 4" square blank box cover gets put on the relay enclosure itself to finish the job.

  • WOW.. Lots of info here. I really appriciate this help. --- Even though my new relay says (UL us listed) on it, it looks like my problem is the wire separation. My relay is the 6CWX8
    – bill
    Aug 17, 2021 at 1:16
  • Yeah, that relay is a funky case because it needs to be paired with a mating relay socket to conform to its UL listing; this isn't an issue with the RIB I suggest, although you'll have to put a 1/2" KO in your box to mount it. Aug 17, 2021 at 1:23
  • As this relay (RIBT24P), is a DPDT relay,can i go ahead and use all terminals, since I have 2 carflex cables. A three wire from the pressure switch coming into a 6x6" carlon box,in my garage, and the other (alt irrigation Pwr)in the other,leads from a box above the pressure switch,also coming into the carlon 6x6 box,to feed the pump when the relay energizes. Basically, Pwr coming through the energized pressure switch, will go into the Nc contacts of the relay, and when the controller calls for irrigation power, the 240v standing by at the NO contacts of the relay, will energize the well pump.
    – bill
    Aug 17, 2021 at 2:09
  • @bill -- its probably easier/simpler to have the NO side of the relay simply parallel the pressure switch contacts Aug 17, 2021 at 3:56
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    @bill - it's customary and expected here to say "thanks" by clicking the up arrow next to any and all answers that help you, and clicking the check mark next to the answer that helped you the most.
    – FreeMan
    Sep 16, 2021 at 11:41

I could not tell by your question, but high and low voltage cannot be in the same conduit. High voltage needs to be kept separate from the low voltage. It is understood that they will enter the same control box to attach to the relay. But they need to be kept as separate as possible.

Unless your situation gives you reason to believe that gravity may move the wires in the conduit, then physical attachment is unnecessary.

  • The 24v cable will be kept separate . ordered the RIBT24P today
    – bill
    Aug 18, 2021 at 0:13

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