The problem has occured in the last couple of days. No changes have
been made to the system, so I presume something's broken. My radiators
are very hot even when the room stat is turned down. The Potterton
Netaheat boiler burns almost continuously. Strangely the hot water
temperature does not seem excessive, though I did turn down the boiler
stat a bit. The cold water seems heated rather more than usual. The
system uses a 2 way bypass valve and pump. There are no TRV's. The
boiler stat seems to respond, the room stat is having no effect (though
I can hear it click many degrees away from the 20 deg norm).
Any suggestions are welcome.
TIA

jd wrote:
The problem has occured in the last couple of days. No changes have
been made to the system, so I presume something's broken. My radiators
are very hot even when the room stat is turned down. The Potterton
Netaheat boiler burns almost continuously. Strangely the hot water
temperature does not seem excessive, though I did turn down the boiler
stat a bit. The cold water seems heated rather more than usual. The
system uses a 2 way bypass valve and pump. There are no TRV's. The
boiler stat seems to respond, the room stat is having no effect (though
I can hear it click many degrees away from the 20 deg norm).
Any suggestions are welcome.
TIA

2 way bypass valve? Don't you mean a 3-port valve? These are well known
as being unreliable.
Often its the synchron motor which can be changed without draining the
system. See/listen if the valve moves when the roomstat or cylinder stat
are manually operated..
At each end of travel it should click as it operates microswitches.
These control the boiler.