Over the last couple of weeks there have been a couple of days when my hot water cylinder didn't get heated in the morning. My central heating is working fine however. I've been investigating it and have found something puzzling.
When I first moved into this house over 20 years ago I replaced the analogue room 'stat with a 7-day programmable one. I then set the heating to continuous and let the 'stat take care of the timing. The hot water was left at timed, running once a day in the early hours. Everything has been fine for all those years until a couple of weeks ago.
Three times now the hot water cylinder has not been heated in the morning. What I've now discovered is that if I advance the hot water on the controller or set it to continuous nothing happens even if I wind the thermostat up to 80c. I can only get hot water sent to the cylinder if the heating is off on the controller (and this is the case even though the 'stat is not calling for heat).
Does this makes sense? And if it's to be expected why has this only now reared its head after 20 years?
My first thought was to blame the actuator since I've had two or three replacements over the years but in this case it seems more like the controller that's developed a fault.
Update: The actuator is a Drayton M1. If I manually move the valve to open with CH on (no heat call) and HW off I can pull the lever against the spring. There will be a click at end of travel. Releasing the lever causes it to be pulled back and when it comes to rest it appears to be locked solid. In this state switching HW on does nothing.
However if I leave the system for a couple of minutes when I come back the lever can be moved again. Interestingly in this position (if I don't move the lever manually) switching HW on activates the motor and the pump runs.
So it seems like there's some kind of 'interlock' which comes into play after the CH is on. Could this be the pump overrun? And could it be that sometimes the overrun is locking HW out permanently? I'd be a bit surprised because the HW is set for 4am to 5am and although the 'stat has optimum start I doubt if it's ever felt the need to wake the heating up that early recently. I happened to get up at 6:30am last Saturday when it was 1c outside and the heating still hadn't come on.
When I first moved into this house over 20 years ago I replaced the analogue room 'stat with a 7-day programmable one. I then set the heating to continuous and let the 'stat take care of the timing. The hot water was left at timed, running once a day in the early hours. Everything has been fine for all those years until a couple of weeks ago.
Three times now the hot water cylinder has not been heated in the morning. What I've now discovered is that if I advance the hot water on the controller or set it to continuous nothing happens even if I wind the thermostat up to 80c. I can only get hot water sent to the cylinder if the heating is off on the controller (and this is the case even though the 'stat is not calling for heat).
Does this makes sense? And if it's to be expected why has this only now reared its head after 20 years?
My first thought was to blame the actuator since I've had two or three replacements over the years but in this case it seems more like the controller that's developed a fault.
Update: The actuator is a Drayton M1. If I manually move the valve to open with CH on (no heat call) and HW off I can pull the lever against the spring. There will be a click at end of travel. Releasing the lever causes it to be pulled back and when it comes to rest it appears to be locked solid. In this state switching HW on does nothing.
However if I leave the system for a couple of minutes when I come back the lever can be moved again. Interestingly in this position (if I don't move the lever manually) switching HW on activates the motor and the pump runs.
So it seems like there's some kind of 'interlock' which comes into play after the CH is on. Could this be the pump overrun? And could it be that sometimes the overrun is locking HW out permanently? I'd be a bit surprised because the HW is set for 4am to 5am and although the 'stat has optimum start I doubt if it's ever felt the need to wake the heating up that early recently. I happened to get up at 6:30am last Saturday when it was 1c outside and the heating still hadn't come on.
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