Pentair MasterTemp default to 70/pool 95/spa since I installed remote

I tried

New member
May 28, 2024
4
Los Angeles
Pool Size
30000
Surface
Plaster
Chlorine
Liquid Chlorine
Help! I installed a little wifi switch (a Thermomart DTH101-NP, pictured) (removed jumper, wired two wires out to remote, also pictured) to turn my heater on and off and set a range, which requires you to turn the heater all the way up and then you can set the range on your phone. It's all great except for ... now these defaults of 70 and 95 on my heater panel pop up every time the power goes off and comes back on. I replaced the jumper to see if this was permanent, and the heater is back to normal, holding the last set temp as usual. I followed the advice on this forum which seemed to suggest to sort of wire it 'hot' (I'd turned the heater off at the panel initially) by replacing the jumper, turning on the heater and turning both pool and spa all the way up, then removing the jumper and adding the two wire setup back and ... no joy.

Since the 'spa' setting holds at 95, that would be adequate if only the switch turned on the spa. The remote turns on 'pool'. Either setting heats my pool the same. So my question: how to get the heater to retain its last-set temp? Or, how to get the remote to turn it on to 'spa' instead of 'pool?' Or, is there a better, more specific or elegant way to wire it in other than the fireman's switch? Thanks!
 

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The heater should turn on in the last mode it shutdown.

Press SPA ON and it will run using the spa temperature setting. Let your switch turn it off. The next time your swicth turns the heater on it should turn on in SPA mode.

Check what the maximum setpoint is set to on the board. The heater comes factory set with a maximum temperature set point at 78° F (25.6 c). for the pool mode and 100° F (37.8 C) for spa mode. The Installation Manual describes how to increase the maximum temperature set point of the pool and spa. It involves unbolting and removing the door panels, accessing the control panel board on the underside of the top cover, and locating the yellow button on the corner of the control board.

Do you have a genuine Pentair PCB in the heater?
 
The heater should turn on in the last mode it shutdown.

Press SPA ON and it will run using the spa temperature setting. Let your switch turn it off. The next time your swicth turns the heater on it should turn on in SPA mode.

Check what the maximum setpoint is set to on the board. The heater comes factory set with a maximum temperature set point at 78° F (25.6 c). for the pool mode and 100° F (37.8 C) for spa mode. The Installation Manual describes how to increase the maximum temperature set point of the pool and spa. It involves unbolting and removing the door panels, accessing the control panel board on the underside of the top cover, and locating the yellow button on the corner of the control board.

Do you have a genuine Pentair PCB in the heater?
I do! Other than the switch I added, it's all original factory equipment except for a flue stack thermistor (?) I replaced 4 years ago. The maximum set point on both pool and spa is 104.

Unfortunately I can have it in SPA mode ... but no matter how it's turned off (manually or via the switch) it comes back on in pool mode at desired temp of 70. Yet when I disengage the remote and replace the jumper, it performs as it should (manually only, obv) with the heater retaining its last setting. I'm stumped!

Edited to add: is there a minimum setpoint capability?
 
Last edited:
SOLVED!
It needed a new board. I checked the manufacture date on my heater and it was installed in 2007 ... I knew it was longer ago than I could remember, but since the heater is at the end of its life expectancy (and beyond!) I got a used/good Pentair board on Amazon for $175, popped it in and my problem is solved. Thanks for your input and I hope this helps someone else searching for this same answer.
 
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