Mastertemp 400 Question

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S

SteakWit

0
May 2, 2018
19
PA
Pool Size
30000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi,

I have a Pentair MasterTemp 400 (installed new in April 2015). The pool heats just fine. I can get the entire 30,000-gallon pool to 90 degrees. We use the heater a lot in the spring and fall.

Recently, when I heat the spa, however, the temperature only gets to about 95 degrees and then the heater turns off. The heater display says 104 degrees. I have no errors and the service light is not on. I confirmed with a handheld thermometer that the spa temp is actually 95 degrees. This is a recent problem. A few weeks ago the spa worked as expected.

After looking online, I suspected that I had a bad Thermistor. I replaced that, but it did not fix the problem. My next step is to replace the Thermal Regulator and then the High Limit Switch (I ordered both from Amazon).

My question is, am I missing something? I really thought that replacing the Thermistor would work since it seems like for safety reasons the heater is turning off since it thinks the spa is 104 degrees.

Thanks,

Andy

*********************************************
30,000 Gallon Pool
MasterTemp 400 Heater
Jandy VS FloPro variable speed
Pentair FNS Filter
Polaris PB4-50 Booster Pump
Hayward CL220 Auto Chlorinator
Jandy iAquaLink
Zodiac color changing LED pool lights
*********************************************
 
So just to check a few things, the heater itself is set to 104 as you have automation, correct? What does the automation say the temp is? Before replacing the thermal regulator, you can pull it to and inspect it. You can also check it's operation by putting it in hot water and see if it opens up. If it opens, then it is good. As for the high limit, you can bypass it temporarily with a jumper wire and see if the unit will heat past the 95 temp.
 
Does the heater display start lower and rise as the temperature rises?

Does the display stay about 9 degrees above actual?

Is 104 on the display the set temperature or what the heater is reading as the water temperature?
 
JamesW said:
Does the heater display start lower and rise as the temperature rises?

Does the display stay about 9 degrees above actual?

Is 104 on the display the set temperature or what the heater is reading as the water temperature?
Click to expand...

I have been running the heater on the whole pool since yesterday. [(Crazy Warning :) . . .] The Poll temp is set to 92. The Pool auto system reads 90 (and it is 90) and the Heater reads 93. That is all great - no issues. Heating the pool is no issue.

If I turn on the spa, however, (even if I am not heating the whole pool to a crazy temp), the spa gets to 95 and the heater turns off (with the heater reading 104 and the automation reading 95). Last week the pool was 75 and the spa got not hotter than 95.

So to answer your question, it is not a constant 9 degrees above actual. Also, since the heater is controlled by automation, I tried to change the temp on the heater but it is locked out (the up-down buttons are not responsive).

Thanks,

Andy
 

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JamesW said:
I'm thinking that you might have a bad membrane pad and control board, but I'm not sure.
Click to expand...

@JamesW: Would you bother replacing the High Limit Switch and Thermal Regulator or would you just replace the membrane pad and control board? I now have all 4 parts in hand.

Andy
 
Since the heater shows 104, the heater is supposed to shut off. The first thing to check is the thermistor, but you have done that. I don't think that it's the high limit, but it might be.

Since you have all 4, it's probably worthwhile to replace them.

However, if it works, you won't know what the issue was.

Since the membrane pad is unresponsive, I think that that's probably bad.

Since a new thermistor didn't resolve the temperature reading, I would think that the control board is bad.
 
The heater membrane pad should be non responsive with automation if my memory serves me correctly. The heater temp should of been set to 104 maybe before automation was connected then temperature would be set off automation.
 
Assuming that they're using the fireman's switch, the buttons should remain responsive.

I think that the water temperature is being displayed as 104 when the water is actually cooler.

The heater is probably set to 104 but that's not the default display.
 
I replaced the membrane pad and control panel and it now works. Interestingly, the membrane pad was disconnected. The installer must have set both pool and spa to 104 and then unplugged the pad since I use automation. Is that typical?

I opted to not replace the High Limit Switch or Thermal Regulator since my symptoms were not consistent with a problem with either.

Andy
 
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