Description

This is the genuine Sta-Rite stack flue sensor, part number 42002-0024S, for Max-E-Therm pool heaters. It fits models SR-200, SR-333 and SR-400.

What it does

The stack flue sensor reads temperature in the flue and reports it back to the heater control. If exhaust temperature runs higher than the design allows, the control shuts the heater down. That protects the heat exchanger and the venting from damage, and it is why a heater will refuse to run on what looks like a healthy day.

Diagnosing it

When a Max-E-Therm locks out on a stack or high limit fault, the sensor is the first suspect, because a failed or drifted sensor reports temperatures that are not there. It is worth checking the flue path and the exchanger for soot or restriction at the same time, since a genuinely overheating stack produces the same symptom for a very different reason.

It is a new OEM part and installs in place of the original.