I have recently had my system drained to fit a new bathroom. Since then the hot water has been too hot. I tried turning down the cylinder thermostat to 50 degrees. It had no effect, the boiler continued to heat the water. I guessed the problem was the thermostat. I have replaced it with a brand new one. It didnt solve the problem. If I gently press the bi-metal strip on the thermostat it works correctly and switched off the system. So the cylinder thermostat appears to be ok but it isnt getting hot enough to operate the switch. I have tried touching the cylinder where the thermostat usually sits and it is getting quite hot but not too hot to touch. Could it be an air lock caused when the system was refilled or is there another explanation. i am now really confused, any help would be apreciated

Steve B, August 2008

After further checks, it seems to have been caused by a sticking 3 way motorised valve. After resetting the valve, the system seems to be working correctly.

Steve B, August 2008

Have you bled the valves at the top of the pipes in the loft? There could be two or three of them. That has caused me problems in the past. Getting rid of the air solved it.

Chicks Fan, August 2008