I have a problem with my central heating and hot water and I'm hoping I can get some advice. This is going to be quite long, but I want to give as much relevant info as possible. Thanks in advance.
The problem I first had was that my central heating was permanently on, even with the control panel set to off. Before this problem occurred, the system was working as expected and had been OK since I bought the house 13 years ago. I searched google and the various forums, including this one, seemed to suggest that the problem could be with the mid position valve/actuator. I looked at the lever on the unit and it seemed to be stuck on H. I opened the housing and could see that one of the resistors had partially come away from the circuit board and looked black, so I was confident that was where the problem was and it would be a simple case of replacing the unit. I removed the unit from the 3 port valve to check that the spindle hadn’t seized and it seemed fine. So, as a temp solution, I had to turn the power to the boiler off to stop the radiators getting hot.
My original mid position valve had the part number 679H340-30L0, so I bought a replacement with the part number MA1, thinking it was a direct replacement. Unfortunately, although the inards look basically the same, the housing is different and won’t fit on my 3 port valve. So I removed the circuit board, microswitch, motor and wiring from the new part and fitted it into the old housing. I connected the wires to junction box, making sure it was wired exactly as it was before I touched anything (I took a photo to be certain). I turned the power back on and checked that everything was working. With the central heating turned on at the control panel, the lever on the actuator moved from W to H. I waited a few minutes to make sure that the radiators were getting warm, which they were. I switched the central heating off, waited 10-15 mins and the radiators cooled down. I then went through the various different options (CH on, CH off, HW on, HW off, CH and HW on, CH and HW off etc). Everything seemed to work as expected. I then turned the CH on and left it on for a few hours, thinking the problem had been solved. When I came to turn the heating off at the control panel, the lever on the actuator stayed at H and the heating stayed on. Pulling my hair out at this point! I turned the HW on at the control panel and the lever moved to W. I then turned the HW off and the lever stayed at W. The radiators cooled down, so I thought I at least had a temporary solution to the problem with the radiators being permanently on. However, it now seems that hot water is still being requested!
So I’m now wondering if I’ve got very unlucky and the new circuit board or micro switches are faulty. Or maybe it’s something else?
Below is the photo of my junction box. I notice that one wire, indicated by the arrow, isn’t connected to the choc bloc. I removed the single wire that is in the choc block, expecting to see broken bits of wire from the other cable, which would have indicated that the loose wire was was originally connected and had been snapped off, but that wasn’t the case, so I have left it as I found it for now. Perhaps that wire is the cause of the problem though? The junction box is in a position where it can easily get knocked, so it’s feasible that’s what has happened and a wire has come loose, but I don’t want to wire it up without being certain.
The problem I first had was that my central heating was permanently on, even with the control panel set to off. Before this problem occurred, the system was working as expected and had been OK since I bought the house 13 years ago. I searched google and the various forums, including this one, seemed to suggest that the problem could be with the mid position valve/actuator. I looked at the lever on the unit and it seemed to be stuck on H. I opened the housing and could see that one of the resistors had partially come away from the circuit board and looked black, so I was confident that was where the problem was and it would be a simple case of replacing the unit. I removed the unit from the 3 port valve to check that the spindle hadn’t seized and it seemed fine. So, as a temp solution, I had to turn the power to the boiler off to stop the radiators getting hot.
My original mid position valve had the part number 679H340-30L0, so I bought a replacement with the part number MA1, thinking it was a direct replacement. Unfortunately, although the inards look basically the same, the housing is different and won’t fit on my 3 port valve. So I removed the circuit board, microswitch, motor and wiring from the new part and fitted it into the old housing. I connected the wires to junction box, making sure it was wired exactly as it was before I touched anything (I took a photo to be certain). I turned the power back on and checked that everything was working. With the central heating turned on at the control panel, the lever on the actuator moved from W to H. I waited a few minutes to make sure that the radiators were getting warm, which they were. I switched the central heating off, waited 10-15 mins and the radiators cooled down. I then went through the various different options (CH on, CH off, HW on, HW off, CH and HW on, CH and HW off etc). Everything seemed to work as expected. I then turned the CH on and left it on for a few hours, thinking the problem had been solved. When I came to turn the heating off at the control panel, the lever on the actuator stayed at H and the heating stayed on. Pulling my hair out at this point! I turned the HW on at the control panel and the lever moved to W. I then turned the HW off and the lever stayed at W. The radiators cooled down, so I thought I at least had a temporary solution to the problem with the radiators being permanently on. However, it now seems that hot water is still being requested!
So I’m now wondering if I’ve got very unlucky and the new circuit board or micro switches are faulty. Or maybe it’s something else?
Below is the photo of my junction box. I notice that one wire, indicated by the arrow, isn’t connected to the choc bloc. I removed the single wire that is in the choc block, expecting to see broken bits of wire from the other cable, which would have indicated that the loose wire was was originally connected and had been snapped off, but that wasn’t the case, so I have left it as I found it for now. Perhaps that wire is the cause of the problem though? The junction box is in a position where it can easily get knocked, so it’s feasible that’s what has happened and a wire has come loose, but I don’t want to wire it up without being certain.
