I managed to find a brand new replacement thermostat.
It was advertised as being for a Ravenheat boiler rather than a Glowworm Fuelsaver MK2 but it's actually the exact same Ranco C77p0102.
When it arrived, I checked the calibration using pan of water and an accurate thermometer.
The results are with the temperature control set to the highest setting (=5).
The boiler switches off @ 77 degC.
The pump overrun switches at 70 degC.
I was surprised that the pump overrun temp is so high.
Now I'm wondering if the calibration is within spec.
I still have been unable to find any documents that specify the correct factory settings.
It was advertised as being for a Ravenheat boiler rather than a Glowworm Fuelsaver MK2 but it's actually the exact same Ranco C77p0102.
When it arrived, I checked the calibration using pan of water and an accurate thermometer.
The results are with the temperature control set to the highest setting (=5).
The boiler switches off @ 77 degC.
The pump overrun switches at 70 degC.
I was surprised that the pump overrun temp is so high.
Now I'm wondering if the calibration is within spec.
I still have been unable to find any documents that specify the correct factory settings.