Pentair Mastertemp 300 Heater Won't Turn Off

Jump to latest Follow Reply
D

DeBo22

0
Jun 17, 2018
12
sewell, nj
Pentair Mastertemp 300

I haven't used this heater in a couple years as I couldn't get it to turn on with the buttons on the display. I figured i needed to replace the switch membrane, but never got around to doing it as we haven't needed to heat the pool.

All of a sudden this morning I heard and felt the heat from the heater running. The display is working. However it won't turn off. I may or may not still need the switch membrane, but my bigger issue right now is that I can't turn it off. I can't turn off the breaker as it is on a dual breaker with the pool pump and also on the same timer.

Where is best to disconnect the power to the heater until I fix the membrane to see if that's what's needed?

Should I disconnect the wiring where it comes into the heater? Or can I take the trip brace that connects the pump and heater together in the breaker box?

IMG_2039.JPG
 
Last edited:
Turn off the gas valve. The heater will shutdown.
 
Pull the Fireman's Switch wire (Yellow Jumper Wire) so that the heater is not trying to turn on.

Even if you shut off the gas, it might still try to run and turn on the blower and go through a startup sequence with the blower and ignitor.

1719848574662.png
 
JamesW said:
Pull the Fireman's Switch wire (Yellow Jumper Wire) so that the heater is not trying to turn on.

Even if you shut off the gas, it might still try to run and turn on the blower and go through a startup sequence with the blower and ignitor.

View attachment 591555
Click to expand...
My wiring looks a little different (not sure why - could it have to do with how it's hooked up through the timer and same breaker as the pump?) I want to make sure I pull the correct wires. Which should I pull?
IMG_2042.JPG
 
Last edited:

Enjoying this content?

Support TFP with a donation.

Give Support
Once you get everything shut down and the power is off, you can disconnect power to the heater if you want.

Disconnect the power wires and use wire nuts to cap them off.



 
I think the wires are going to the timer box. Trying to add pics but they are too big of a size. Going to shrink them.

Also, when I went out to snap the pics, the heater was not running (but is still on).
Did it just need to go through a few cycles of firing the igniter/blower until it realizes theres no gas and shuts off?

If so, can I leave it like that until tomorrow when I get the new membrane (the display on the membrane is still working, but I get an R13 error and the buttons don't seem to work properly)
 
JamesW said:
Normal boot up is 888, 128 and then rX where X is the software revision number.

R13 is the software revision number.
Click to expand...
ahh gotcha...yes i get the 888, 128, then the r13
none of the buttons seem to do anything on the heater though. it shows the pool temp number in the display.

I've always assumed i needed the new membrane. Not sure why it just started working again? Should I still replace the membrane? They're pretty cheap so that might be an easy first attempt.
 
So, should I pull the firemans switch in the heater, or the timer, or disconnect the power to the heater as the videos you showed me, or just let it stay as is for now with the gas valve turned off and let it run like it is now (no blower or heater running) until I try changing the membrane tomorrow?
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply