Drayton mid position actuator issue

[catfordbags]

Hi All .... I am assuming that it is a coincidence but yesterday we had our gas metre moved. Since the reconnection. When the boiler is supposed to be heating up the tank, it is actually turning the central heating on.
This led me to the Drayton mid position actuator.

it appears that the black tab indicator was stuck on the central heating mode. So after a bit more research it seems that i had to figure out whether the actuator was faulty or the brass valve.

Well i've taken the actuator off and it rattles which makes me think i need a new acculator but i then had a look at the brass valve. I can manually turn it to the right (i assume that is heating mode)

and i can turn it straight (which i assume is heating and hot water mode)

But I can't turn it to the left (hot water mode).

Now I don't know whether it is the actuator or the brass valve that is buggered.

Any help would be much appreciated. Thanks in advance.

CB

 

[jackthom]

With the actuator removed from the valve body. By using the programmer and tweaking the thermostats, select the three alternatives in turn. ie DHW only, Heating only and Both (it may be best to turn off the power to the system before each trial, at which time the actuator should definitely return to W).
In each case check the actuator is indicating what you would expect.

 

[catfordbags]

Cheers Jackthorn ... yep, did as suggested and if i force the black lever over into the left hand position then put on the HW it will stay there. If in then put on the CH it moves across to the middle. Then if i turn the HW off, leave CH on it moves to the right.
From this point, nothing that I do turns it back to the middle or left. So i am happy now that the actuator is bust and I should open it up and have a look.

During this test i also looked at the actuator housing where the brass spigot fits and i think i have answered one of my questions. I had assumed the three directions of the brass spigot would be 10 o'oclock, 12 o'clock and 2 o'clock. But now i realise they are actually 12 o'clock, 1 o'clock and 2 o'clock and if this is correct then the valve is still working correctly.

 

[jackthom]

Have you tried removing all system power when the actuator appears to be stuck in the CH Only position? (It could be held there by the DHW satisfied voltage)

 

[St0rmer66]

If you have a rattle from the actuator then one of the springs that returns it to hot water has probably snapped off the post.

 

[catfordbags]

Uummm.... I think I am quite happy that the actuator is broken. (I have tried turning it off at the mains)

I am just worried that the brass valve is jammed as well. As in the two photos above, I can only manually move it between a 12 o'clock position and a 2 o'clock position. In either of those positions it seems to be heating up both the water tank and the radiators.

My problem is that I think I can replace the actuator no problem. However if the valve also needs replacing then that is time to call the plumber. Anyone got any thoughts about the valve.... The extent to which I can currently manually turn it and the fact it seems to be feeding both the HW and the CH ?

 

[St0rmer66]

If you can turn it by hand without tools then it's probably fine. If you have the actuator off then it will pass down both because there's nothing actually holding it in the position no matter where you place it. The spring holds the valve tightly shut on hot water and the motor keeps it under tension for the central heating position.

 

[BBJonW]

I'm leaving this information on a thread where someone may find it useful. I recently had a problem with a Drayton MA1 Mid-Position valve, whereby when my hot water was on, it also ran the central heating i.e. the valve would stick in the mid-position. Since the 3-way valve itself appeared mechanically fine, (around 45 degrees of light travel with a pair of pliers covering all three positions) I first changed the motor in the actuator (around £15 from Screwfix), and then the programmer (for a spare unit I happened to have). Neither of these changes affected the problem. I therefore turned off the 240V and dismantled the actuator mechanism itself. It took a while to figure out how it works, but basically the spring-loaded gearing sits between TWO micro-switches. These micro-switches limit the travel of the gearing - one activates every time the motor runs, limiting one end of travel, whilst the other is an 'emergency stop' which (looking at the mechanism) should never be triggered. I don't know how it could possibly have happened, but the 'emergency stop' micro-switch had seized in the 'on' position i.e. depressed. This was NOT obvious, and I don't know how it could have happened since it could only get depressed by either a fine knife blade inserted into the mechanism, or an impossible degree of travel of the actuator gearing. However, freeing the micro-switch with a little WD40 allowed the motor to drive the gearing fully to the HW position, and completely resolved the problem. Therefore, if you have a strange problem with your central heating system which seems to point to the actuator but which does not respond to logical fault-finding - check the micro-switches!