Boilermate 2000 PHE Pump Switching on/off 50/55 instead of 70/75

Hi,

Apologies if this has been answered before...tried looking for similar.

My Boilermate 2000 PHE_T2 Sensor suggests that the Heat Exchanger Pump should switch on/off at 70/75 degrees.
However, for a while now the hot-water supply has been much cooler than normal and inconsistent. By running the hot water and using the ACB to check the sensor temps, I can see that the PHE pump is actually kicking in at 50 and off at 55 degrees, consistently. The result is the hot water supply(sensor DHW_T3) fluctates between 40 and 45%, in sync with the pump switching on/off.

Is that likely to be a sensor issue or something on the ACB, as the temperature readings are presumably correct.

Regards,
Bernie

Hi Bernie

This sounds very much like a hot water sensor that is failing (part number GT153) and will need replacing.

Hi, Thanks for the prompt reply. I will take your advice and replace the sensor. I just have one nagging thought which may just be my ignorance of such things: if the sensor is just there to indicate temperature and the temp display for that sensor is showing between 50 (when pump actually starts) and 55 (when pump actually stops), why would the system prompt on/off at these temperatures when the values displayed as being set on the system for when this should happen are still showing as 70/75? I cannot understand why a broken sensor would cause the switching on/off to be at wrong but consistent temperatures, different to those settings on the system. Does the sensor do something more than just indicate temperature to the system?