Drayton 3-way Port valve stuck

[NeilF36]

I recently noticed that the Central Heating was not coming on when it should have along with the set program. The water came on okay and the central heating at the time. The water can come on, on its own, but the central heating can not come on on it own. I turned off the electric and the bar over to the water but when I turned it back on the bar went to the middle. So, now I know that when I turn the water on the central heating comes on as well. However, when I turn on the central heating nothing comes on. I now have to heat water for no reason if i need central heating.

If the machine is broken, then this is fine, but is there anything I can do to at least check that it is surely broken? Or can i do something to rectify it? I tried to push the bar over to the central heating but i noticed this was very stiff. Is this bar supposed to be in the middle anyway? I have a thermostat downstairs also.

Any info will be much appreciated.

 

[oilman]

I take the head off and use a spanner to see if things will move. If it doesn't move it is possible to get it moving, but it also indicates it is time for a new valve.

 

[NeilF36]

So, i took the motorised valve off and then looked at the spindle. I put the plier onto this where I feel it turned 90 degrees at most but i did not force it. Would you know how much this is supposed to turn (clockwise or anticlockwise) from its original position. I have a feeling if this jammed the motorised valve would stop. With not knowing how far round the spindle goes it is hard to know if it is jammed. I am worried about getting a new motorised valve attaching it but it can't turn the spindle.

Thanks for any help.

 

[DaveHerns]

It only turns a fraction. You probably need a new head. A new complete assembly was cheaper at Screwfix when I got one. Your symptoms are the same as when my mum's valve failed.

 

[stem]

It most likely is the motorised valve, however, I have come across two instances where the batteries have become discharged in the room thermostat and were not switching the heating on. One of them (Drayton Digistat 1) also didn't show the low battery symbol in the display, despite the instructions saying it should. There must have been enough power to energise the display, but not enough to operate the switching relay. New batteries saved the day.

It's always worth while checking with a multimeter that power is getting to a device first before forking out for an expensive and possibly unnecessary spare part.

If you don't have a battery powered thermostat, you can of course ignore this.

 

[NeilF36]

I do not have a battery powered thermostat downstairs but this has got me thinking how much this would change things if it was broken. It is an old SwitchMaster. Now, if this is broken would it stop the actuator working. Does it work like that? I guess if just turn on directly the Central Heating the Thermostat would not be involved. I have done this (just directly turn on CH) before and nothing happened, so this would discount this.

So, I am not stuck with whether to get a new motor for the actuator or whole new unit. Whether the valve below it is working too. And the thermosstat.

Umm, a little confused.

 

[stem]

Sorry to have confused you. It's unlikely to be the thermostat if it's a mechanical one.

Turn it up and down, can you hear it click? if so, it is likely working.

However, if you have a multimeter and are competent to use it they are easy to test. Or you could put the two switching wires in the same terminal (but not the neutral if you have a neutral at the thermostat) that effectively by-passes the thermostat and the heating will stay on, regardless of the temperature.

 

[NeilF36]

So i have the thermostat on at 15 degree and the power on for the central heating but nothing. It did click by the way for the thermostat.

 

[MeldrewsMate]

To answer a previous question, the valve stem, when seperated from the valve body, should rotate easily between finger and thumb, approximately 90 degrees. If it needs a spanner to move it, then it is most likely too stiff for both the motor to open it, and the springs to close it.
The other fault may be that the internal microswitch has failed and, although the motor can open the valve, the valve head will then fail to give the required feedback to the control system, and there will be no call for heat (until the hot water valve supplies it).

 

[NeilF36]

Can i bypass the thermostat to check the heating is working? When i turn on the heating directly it does not work now. I would like to nail down what component is not working.

 

[MANDATE]

You can by pass the room stat, but I don't see how it will help you.
I understand you get heating but not on its own.
To get heating with hot water means the valve has moved from HW only to mid position so the stat and the motor are not the problem.
The problem is lack of power to drive the motor from mid position to heating only, this is caused by a faulty micro switch or it could be the valve does move as it should but fails to start the boiler. This is due to lack of power being supplied from the valves second micro switch.
It appears the valve spindle is not stuck, so replacement actuator head should solve your problem.
Make sure to remove power from boiler when replacing cause one wire in the head remains live when HW and CH are both switched off.

 

[stem]

Mandate's right. Sorry I missed your comment that the heating is coming on when the hot water is also on. (I think I got your thread mixed up with another one ) In your case the thermostat will be signaling the motorised valve to move to the heating position so the thermostat will be working OK.

So, its back to the motorised valve not reaching the heating only position, or a faulty microswitch not switching the boiler on when it gets there.

 

[NeilF36]

Great thanks for your help. I think I will buy a new actuator.

 

[DaveHerns]

Buy the complete valve, the price is the same and you may need the valve body. You can compare the force to move the shaft old -v- new