In the recent cold weather my CH hasn't been able to get the house up beyond 19 degrees, so I turned up the temperature control on the boiler up from about 70% max to about 85% max. Sometime during the night the boiler locked out with an overheat fault. Reset it, turned the temp down a smidge, and turned the pump up from setting 1 to 2. Boiler hasn't locked up since, but house barely up to 20 degrees. All rads a quite warm (no cold spots so don't need bleeding), but not very hot. The system was balanced when I had a new boiler installed 8 years ago ( Worcester Bosch Greenstar 24Ri, new pump, new pipework and Honeywell DU145 Bypass valve). The CH and HW zone valves are operating ok, TRVs all fully open.
In poking about I noticed that the boiler out and return pipes were about the same temp, as was the pipe either side of the bypass valve (IR thermometer, black tape on pipes).
The bypass valve is set to just under 1, as done by the guy who installed the system. I'm thinking that maybe that valve has stuck part open, hence the return temp to the boiler being too high.
I've run the system up from cold, and the output pipe from the valve pretty much tracks the temp of the boiler output (lagged a degree or so, but probably the drop across the pump and pipes).
What do you guys think, I've read of a few bad reports on these DU145 bypass valves. Anything else you think I should try or test? Can give more details of system if needed.
In poking about I noticed that the boiler out and return pipes were about the same temp, as was the pipe either side of the bypass valve (IR thermometer, black tape on pipes).
The bypass valve is set to just under 1, as done by the guy who installed the system. I'm thinking that maybe that valve has stuck part open, hence the return temp to the boiler being too high.
I've run the system up from cold, and the output pipe from the valve pretty much tracks the temp of the boiler output (lagged a degree or so, but probably the drop across the pump and pipes).
What do you guys think, I've read of a few bad reports on these DU145 bypass valves. Anything else you think I should try or test? Can give more details of system if needed.