Faulty Drayton Mid Position Valve?

[HughCallaway]

Hi,

I hope that someone can help me and point me in the right direction.

My central heating has recently stopped working from coming on by the room thermostat. I thought the issue might be a dodgy thermostat as I managed to get it working every now and then by switching off the boilers electrical supply and turning up the thermostat to the max. I've replaced the thermostat but the problem still exists.

What I then did was to switch off the hot water on the programmer and the boiler started and central heating came on.

I've looked at the wiring and now wonder if its the Drayton Mid Position valve or maybe the programmer. Does the Drayton Mid Position valve control the electrical supply to the room thermostat?

I realise I might need to get a plumber in but would like to try and understand the problem first.

Any help would be gratefully received.

Thanks

Hugh

 

[lame plumber]

based on your comprehension of how a system works at present you would be best served by calling a decent plumber to check out why your system isnt working.

 

[doitmyself]

Can you have heating and hot water working at the same time? (That's not just turned on at the timer.)

What happens if you then turn the HW cylinder thermostat down to minimum?

 

[bigads28]

On the side of your valve head there is a little black marker that moves when you put the heating and water on. Best way to see if it's working correctly is to put the hot water on and heating off and the marker will go to one side of the valve. Do the opposite water off and heating on the marker goes to the other side. Once you are happy it goes from side to side put both on and it will go to the middle. The marker might have A & B or HTG & HW it depends, most important thing is that it moves.

It's better you try this once you've used a decent bit of hot water so you are sure it comes on and the room stat to max.

 

[craigy]

I second lame plumber, you might spend an hour trying to work out the issue to no avail. An experienced heating engineer will diagnose in no time just get him in and he will tell you.

 

[HughCallaway]

Hi, no, when you manually switch on the hot water the central heating goes off after a short while.

 

[HughCallaway]

Hi, thanks tried that - it sometimes does that, but sometimes it doesn't go from side to side when you switch etween the two

 

[HughCallaway]

Got one coming tomorrow I like to have an idea before a plumber comes though

 

[craigy]

When you have both C/H and H/W calling on the programmer, you don't get both?
If a mid position valve will not sit in the mid position then that will be why you get the central heating kicking in as soon as you turn just the H/W off at the programmer. It was never in the mid position in the first place, it's open to H/W only so when you turn the hot off it moves over all the way to C/H. If a mid position valve fails it's mechanics default to the HW position for health and safety reasons, you can't wash with your radiators! This would tie in with the electrics reset working temporarily too, the pcb or motor in the valve has failed. You can try replacing the head of the valve only to dave a drain down.
I could be wrong let me know and good luck