When the blower comes on, check the Stack Flue Temperature.
Maybe the SFS (Stack Flue Sensor) Temperature Reading is higher than it should be and the blower is being turned on to cool down the heater.
I do not know if that is a thing or not, but it is worth checking.
For example, if the SFS (Stack Flue Sensor) Temperature Reading is 180 degrees F on startup, it might cause the blower to come on, but it is not high enough to cause an error of SFS.
Exhaust Gas Temperature
While running, press and hold the On button to display the exhaust temperature (Older Models).
The new models use the Menu to get the SFS.
Here is what the normal exhaust temperature should be:
When the blower starts, but before the heater fires, the exhaust should be about equal to the air temperature.
When the heater fires, it should quickly reach an operating temperature of about 300 to 310 degrees.
Below 250 degrees...very low
250 to 290 ..................low
290 to 350.................acceptable
350 to 480 ..................high
Above 480...................error/shutdown.
Note: HD models can be up to 75 degrees higher.
HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.
If the exhaust gas temperature is higher then normal then water may be bypassing the heat exchanger through a broken bypass valve.
If you hold down the "pool on" button, it stays on 80, then flashes to 40, then back to 80, then the 80/40 reading and E05 indicate that the board is not getting a reading from the sensor.
It's usually a bad sensor or damaged wires.
The following are the LEDs:
- .....PS (Pressure Switch)
- .....HLS (High Limit Switch)
- .....SFS (Stack Flue Sensor)
- .....AFS (Air Flow Switch)
- .....AGS (Automatic Gas Shutoff).
- .....Service System
- .....Thermistor
- .....Heating
- .....Pool On
- ...Spa On
- ...Service Heater.
