This midpoint valve was making a fairly load clicking/ticking noise whenever the central heating was used and continued even when the CH was later turned off. It seemed likely the motor wearing out, as the noise was becoming more obvious, so I got a replacement head. I fitted it and was testing all was working OK with the top off and noticed the motor was being constantly driven when open, and it was getting very hot, really very hot. Thinking there was a fault I did some research and found this explanation.
As you probably all know it's designed to work this way, the motor is constantly driven as per the explanation...
I understand its made to operate this way, though that would be why the motor was worn out and noisy and needed replacement. I wasn't so bothered about the constant power consumption, (6 watts, but lets keep a sense of perspective), it was more that it was being driven when not needed and was unnecessary. I had a look at the Y plan wiring from our boiler manual and saw a nice elegant solution was possible.
The reason the motor stays live and driven is due to the line from 'HW-OFF'. (I've attached a scan to show this). What I've done is modified the wiring slightly and interrupted this line with a small 240v relay that switches with the room stat. Now when CH is ON, and room stat is OFF this line is interrupted and the motor returns to rest, when the room stat calls for heat this line is switched through and the motor opens normally.
CH and HW are operating normally, except now the motor can only be driven open if CH is ON and room sat calls for heat. I'm sure this mod won't meet with everyone's approval, after all the motor was designed to work constantly, but there isn't any need for it to. Also we tend to have the CH time switch on constant, and control the CH with a remote room stat, so you can see the motor would have been mostly driven all day and night in this scenario, now its only driven when needed.
As you probably all know it's designed to work this way, the motor is constantly driven as per the explanation...
I understand its made to operate this way, though that would be why the motor was worn out and noisy and needed replacement. I wasn't so bothered about the constant power consumption, (6 watts, but lets keep a sense of perspective), it was more that it was being driven when not needed and was unnecessary. I had a look at the Y plan wiring from our boiler manual and saw a nice elegant solution was possible.
The reason the motor stays live and driven is due to the line from 'HW-OFF'. (I've attached a scan to show this). What I've done is modified the wiring slightly and interrupted this line with a small 240v relay that switches with the room stat. Now when CH is ON, and room stat is OFF this line is interrupted and the motor returns to rest, when the room stat calls for heat this line is switched through and the motor opens normally.
CH and HW are operating normally, except now the motor can only be driven open if CH is ON and room sat calls for heat. I'm sure this mod won't meet with everyone's approval, after all the motor was designed to work constantly, but there isn't any need for it to. Also we tend to have the CH time switch on constant, and control the CH with a remote room stat, so you can see the motor would have been mostly driven all day and night in this scenario, now its only driven when needed.
