Potterton "Kingfisher CF60 CAT 1N" temperature controller replacement

[Steve19861989]

The boiler thermostat for the above has failed. The thermostat is a SOFAL SL 203.01 and the thermostat probe is integral with the simple on/off switch or relay in a housing. In other words, the complete unit needs replacement. Unfortunately, given the age of the boiler, that item is no longer available.

So to replace, I installed an NTC 10KOHM, 2-conductor, measuring range: -50°C to +200°C sensor with the sensor end in the opening in the boiler previously occupied by the sensor end of the SOFAL unit. The new sensor was connected to an STC-3008 temperature controller which enables the boiler to cycle "on" at a (desired) preset lower temperature and to cycle "off" at a (desired) preset upper temperature. In other words, it now functions in the manner of the old SOFAL unit.

However, with the SOFAL unit, there as a control knob to set the (desired) temperature of the boiler in steps of "0", "MIN, "1", "2", "3", "4" and "MAX". Thus, depending on how cold the weather was, you could set the boiler to cycle "off" from presumably different upper limit temperatures. I have no information as to what are the temperatures associate with each of "MIN, "1", "2", "3", "4" and "MAX" nor do I know what the lower temperature is to cause the boiler to switch on.

Thus, after that long winded discourse, does anyone know what are the boiler "off" temperatures are associated with each of "MIN, "1", "2", "3", "4" and "MAX" and what the boiler "on" temperature is?

Thanks.

 

[oilhead]

Your old thermostat would have ranged between approx 50c to 80c. Decide what flow temp you want in your radiators and set your new unit to that. The old stat was a relatively coarse unit and would have cycled the boiler over a range of approx 10-15c, I can't see any specification for the ST3008 unit, but suspect the hysteresis will be much closer. I can only suggest you play about with it.

 

[Steve19861989]

Thanks oilhead. STC3008 example here: https://tinyurl.com/stc-3008