Motorised valves are out to get me...

[james_smith99]

Hi, trying to understand whats happening with the motorised valves on my CH. Would be very grateful if someone can point me in the right direction (but obviously not to my friendly local plumber just yet)...

Got two valves, as far as I understand it one for downstairs and one for the top two floors. I've had problems with the motor packing in in one of them before (downstairs) so have had to change it in the same valve twice. this has never been too much of a problem.

It went again the other day. I only changed it about a month ago, the motor had actually seized and wouldn't go round so assumed it was a dud and went back to screwfix for a replacement. when putting it in the wire broke off the circuit board so out came the soldering iron and the circuit was restored - happy days I thought...

now I get this. when the thermostat for downstairs tells it to come on, the light in the valve control comes on but nothing happens. the motor doesn't go round to open the valve or turn the boiler\pump on. I've actually got the control box off and open and can see the valve doing sweet FA.

if the upstairs CH circuit kicks in, then the motor for downstairs goes round and (when its actually sitting on it) will open the valve and tries to set the micro switch for boiler\pump. this clicks away constantly - so I think is slipping anyway - but I can't work out why it doesn't work on its own circuit. I could have destroyed the circuit board with my soldering but is it likely to then somehow take commands from the other circuit.

 

[Silentrunning]

If you got the board hot enough to melt adjacent solder you may well have changed a circuit.

 

[piglet11]

What you need to tell us is are you talking about 3-port valves or 2-port valves?
All these valves have a built-in design fault, even Honeywell. The problem is that to keep the valve in the non-default position (the position with no power applied), the synchronous motor is deliberately stalled.
This generates considerable heat that eventually destroys the wiring insulation. In summertime, the valve can be stalled for months at a time. To avoid this, just switch the system power off briefly and the valve goes back to default.
You say the motor is siezed. Are you sure it's not the resistance of the gearbox?
Frankly, if you've had a go at repairing it (what make is it?) then it's time to get a new one.
I'm not a full-time plumber, but I do a lot of electrics and electronics. Y-Plan, S-Plan etc wiring always defeats my plumber mate, so I help him out.
If I were you, and you could run the risk of making things worse, I would replace the valve or actuator wire for wire in your system.
If you end up losing where things were connected, you could be in deep do-do. It always pays to note or photograph things before you attack.
I doubt, but could be wrong, that anyone can properly diagnose the faults you now by the description.
Ref the circuit board. There isn't much on there to destroy but it can be done. There is a diode (might be 1N4003) and a resistor (value escapes me) and 3-port valves are horribly difficult to understand.
I believe that years ago, there was very good detailed description of how the valve works on this forum.
By the time you read it though, you could have changed the offending item. I'm not sure what Screwfix sell as synchronous motor, but I would always get the genuine item "Synchron" and not some cheepo copy.

 

[Tom Tucker]

Most problems that involve a controlled valve electrical circuit, is electrical. You may have misunderstood what you thought you were seeing. After 40 yrs of working with valves, IF you are repacking valves that often replace valve. Tightening packing to stop a leak should be incremental, not tight is good. IF you need to replace valve DON'T go cheap. Replace with direct replacement. IF you don't you'll be chasing your tail.

 

[WyrTwister]

Makes me glad that residental hot water heating is rare in our area !
Wyr
God bless