Temperature issue for Spa

[tbratkovich]

I can't get my spa to heat up above "lukewarm" -- maybe 88 degrees. I have a Pentair MasterTemp 250 heater, ~4 years old, worked fine for years. Now, it reads ~15 degrees hotter on the inflow water temp than the water actually is. For example, when I turn it on, and the spa water temp is actually ~60 degrees, the Pentair LCD screen says 75 degrees. It then proceeds to fire normally and heat the water up to the spa temp setting of 100 deg (or the 104 max), but the actual water temp reached and stabilized is ~85-~88 degrees and it won't get any hotter.

I thought it was a bad thermocouple/thermister (part 42001-0053S) -- but I replaced it with a new one, testing the resistance on both, and both are in spec and read the Ohms for a temperature that 15 degrees lower than what the LCD screen shows (used this table: File:10K thermistor chart.png - Further Reading )

The Control board show no errors. Anyone have any ideas on what is going on or how to fix? Thanks

 

[ajw22]

Put a 10K resistor connected to the temperature sensor wires. If the heater reads 76F then the sensor is bad.

If you don't get a good temperature then check the wires for critters chewing on it or replace the PCB.

 

[DavidArmenB]

I heard that you can recalibrate the sensor inside the panel? Maybe it’s calibrated to -15 degrees so it always shows 15 degrees less than what it reads from the sensor? Check the settings.

 

[ajw22]

Maybe I am confused…

• What is the actual water temperature as measured by a separate thermometer?
• What temperature is displayed on the EasyTouch system?
• What temperature is displayed on the MasterTemp control panel?

 

[tbratkovich]

Hi All, thanks for responding to my thread. It took me a few weeks but I finally got back to this.

ajw -- I put a 10K ohm resistor across the thermistor wires -- panel reads 98 degrees when I do that. So the problem is clearly in the control board (or the wires). I visual'd the wires and don't see anything wrong with them, although the wire harness that includes the thermistor wires is tucked way back there and hard to see all the way through. But looks ok.

The water going in is ~63 degrees +/- 5 deg. It is definitely much lower than the 78 degrees that the panel reads when I have the regular thermistor wired in (and btw I already replaced the thermistor already with a new one... both the old one and the new one give the same wrong reading at the control board display).

David, I thought of a calibration issue but I have not been able to figure that out, or how to set the high limit sensor toggle higher (say to 120 degrees instead of 104) which would make it work fine.

Looks like I am down to replacing the control board. I found one on Amazon for $100, which isn't too bad. Do you guys think that I can replace this myself? I'm an engineer, but not a EE ! I'll report back on how it goes. -- TB

 

[JamesW]

I found one on Amazon for $100, which isn't too bad.

That's going to be a low quality piece of cheap Chinese junk.

 

[ajw22]

I recommend using genuine Pentair MasterTemp parts in spite of the cost.

We have seen too many people try to use knock off boards and have problems that were fixed by installing a Pentair board.

Read…

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[tbratkovich]

Hi All, reporting back. I got the "piece of junk" and installed it today and lo and behold, it works great. Seems to be better than the piece of junk that was the PentAir OEM control board. For now anyway!

Thanks to all that responded and helped.... very cool of you to spend a little time helping on this project.