Raypak 406a sensor failure - but water temperature reading is correct

[pgershon]

My spa heater got a sensor failure error last week. I cleared it by shutting unit off and on. Same issue 2 days later and same fix. 3 more days later it is stuck at sensor failure and cycling power does not reset.

Its gotten colder and issue started when spa water was below 65 degree. Down to 62 today when cant clear error. Only reason I am concerned that it may be something other than just needing a replacement sensor is that the water temperature reading at 62 degrees is correct. If sensor fails, how does unit know water temp?

 

[ajw22]

Are you reading the water temp at 62 degrees on your Aqualink?

The Aqualink has its own water temperature sensor in your pool plumbing separate from the temperature sensor in the Raypak heater.

 

[pgershon]

No, the raypak display says 62. As does aqua link. What confuses me is how raypak could have a reading when it says sensor failure

 

[ajw22]

No, the raypak display says 62. As does aqua link. What confuses me is how raypak could have a reading when it says sensor failure

Maybe @ps0303 knows where the Raypak is doing the temperature comparison. AFAIK it only has one water temperature sensor.

 

[ps0303]

Sounds like the board is remembering the last reading.

 

[ajw22]

I would replace the thermistor in the heater and see if it clears the problem.

 

[pgershon]

Will do - and I'll report back

 

[pgershon]

New the thermistor installed and all is now fine. Old one was rusty when it came out. I suspect pool heater was displaying an old reading as Paul speculated.

 

[ps0303]

New the thermistor installed and all is now fine. Old one was rusty when it came out.

Do you maintain your pool chemistry and if so, do you keep it on the numbers?

 

[pgershon]

I absolutely maintain my chemistry - since July 2021. My pool service very poorly maintained chemistry for the heater's first ten years... pH was frequently well over 8.0, and Calcium was sub 100 (plaster spa). Need to redo finish next spring too.