Pentair MasterTemp wiring into EasyTouch


Gold Supporter
Aug 8, 2020
Falls Church, VA
Can the experts please let me know if the heater is wired incorrectly, I think it is based on what I have been reading. Details below:
  • Pentair EasyTouch 4
  • ScreenLogic 2
  • MasterTemp 175K Heater
I would like to ensure that the wiring is correct and suitable for heater automation control through ScreenLogic 2. As shown below, the heater is currently directly wired into the 2nd (from the top) circuit breaker. Research indicates that the heater power should come off a power relay. I cannot figure out if it should be connected to the pump relay or a separate (aux) relay. I also understand there needs to be a 2 wire connection from the heater (it is referenced as a "fireman's switch") to the EasyTouch. Any advice is recommended...and I will have a licensed electrician/plumber complete the work, I just want to make sure we get it right the first time and the automation works.



Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

There is no reason for your heater to be connected to any of the high voltage relays...

Your heater has something called a fireman's switch or loop.. Basically, the heater sends 24 VAC to a small relay on the main board. (Gas heat connection). The EasyTouch controls the relay based on the amount of heat wanted.. When the ET sees the water temp drop below the temperature you want, the relay closes and the same 24 VAC is sent back to the heater "closing the loop" and the heater fires up. The heater is always on, but not running until the loop is closed. You initial set the heater to full hot and in a remote mode. See heater's manual.

All this is done via a small two wire cable that you have to purchase from your local Home Depot..

You can, if you want, use the ET's load center for the heater's 120/240 volt circuit breaker..

Please let me know if you have any questions about this.


Jim R.


Gold Supporter
Aug 8, 2020
Falls Church, VA
@Jimrahbe Thanks...the way you describe it above is the way that I have it wired up now (the 2nd Pentair C/B you see is the heater) least on the ET side...240 from the ET C/B, and the 2 wire for the fireman's switch ran, but not connected yet. I was just reading so many different variants on the heater wiring I started to question things, many thanks for the advice. This site has been invaluable in my quest to put a hole in my back yard.
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