Max-E-Therm doesn’t fire, no service lights. Panel reads “15”.

[Martin Beck]

Natural gas Sta-Rite Max-e-Therm 200 heater for an in-ground 18k plaster pool with a 2 year old variable speed Polaris pump.
As of a week ago, the heater doesn’t fire, and the membrane control panel doesn’t show a service heater or service system light. The LED alphanumeric display reads “15” which I can’t find any reference to in the manual. I removed the membrane control panel and I don’t see any error lights lit on the underside. The pump clearly has power.

Previous owner installed, so not sure how old. Has worked fine for the past few years. I have checked flow, filter pressure, all seems fine.

 

[ps0303]

So when you power it up, does it show you several numbers? i.e. 128 R 13 or similar.

How cold do you think the water is?

 

[JamesW]

Press the off button, press and hold the up or down arrow for 5 seconds to see if the 15 changes to 59.

Then press pool on, press the up arrow to check the set point and set higher than actual.

Is the heater connected to automation?

 

[ps0303]

Press the off button, press and hold the up or down arrow for 5 seconds to see if the 15 changes to 59.

Yeah that was what I was getting at with the question about how cold the water is.

It could be a thermistor as I had one last week that was reading 1. That was Fahrenheit. Changed out the sensor and then it read 65.

 

[JamesW]

It might be a bad thermistor. However, I would think that it would still fire as long as the set point was higher than the "actual" unless there's a low temperature cut off that won't allow the heater to operate below a certain temperature.

It would make sense for the heater to not operate if it reads 15 degrees Fahrenheit because there's no reasonable way the water could be that cold without being frozen.

Maybe below a certain temperature, it just decides that the thermistor has failed and it won't work.

If that were the case, I would expect that the "Service" light or code would come on.

Do you know if there is a low temperature cut off?