We have an old oil fired boiler with a fully pumped central heating hot water system with two drayton-acl motorised valves (The valves were replaced about 9 years ago). The system works perfectly providing hot water and heat to the radiators when required. The boiler programmer was replaced with a hive system a couple of years ago, but recently the grundfos pump has strarted working continuously. It isn't calling for heat just the pump runs all the time. Any advice of what to try. Thanks.
Hi On some boilers, the pump feed is from the boiler wiring, this is to allow for the pump over run, to dissipate the laten heat , there is a thermostat in the boiler that switches the pump on when it fires up, and off when it cools down, So it’s possible the the pump over run stat if faulty , and not breaking the connection when the boiler cools down, good luck Peter
Traced fault down to the motorised valve for the hot water. Replaced actuator and all working well now.