I visited my parents over the weekend and noticed that there was a loud grinding type noise coming from their heating system. It was coming the pump. Then all of a sudden the hot water stopped working closely followed by the central heating system. So I drained down the system and replaced the pump (old: SMC commodore 130-45 Speed Position Minimum with new: WILO Gold 130mm / 6M Speed Position 2) and the isolation valves on either side because they were weeping. Then I reconnected, filled up, vented pump and radiaitors. The central heating worked fine but no hot water. The bolier fires up when hot water is switched on but then after a short while (30seconds) it switches off. I have two off 2-port motorised valves, one for the hot water leg and one for the central heating leg. Both are working ok. The boiler is a glowworm space saver 75. I have also replaced the thermostat on the hot water tank (old: Drayton CS1 with new: Drayton HTS3)
Does anybody know what I should do as my parents have no hot water.
BJ

BJ, November 2007

we had the same problem with or boiler and it turned out to be the main board inside the bolier

jimjams, June 2010