Central Heating: Replacing Drayton 3 Way Mid Position Valve

[MANDATE]

It's usually the CH that gives problems with 3 port valves, because the valve does not move across to the correct position or if it does the micro switch contacts don't make and stops power coming out through the orange wire.
The micro switches have no bearing on operating for Hot Water.
If CH has not been switched on, the quadrant (which turns the valve) is spring loaded and will return to the HW position.
If the quadrant/valve is stuck at CH and the spring can't return it, then that would have an effect.
The lever is there for a special purpose, nothing to do with the boilers operation. When the system needs filling, both ports need to be open so the lever is used (power is off) to turn the quadrant. There will be resistance due to the return spring and the motor. The lever is put on a latch(manual) and later put back to 'auto'.
If the quadrant is at mid position, then the lever will be floppy.
Perhaps you should be more specific regarding the problem you're having with 'hot water'.
If the boiler does not light when HW is selected, then you need to be looking at the cylinder stat.

 

[loko2468]

Hey everyone, first time poster here, and completely new to DIY, so be gentle please

No matter what settings you set on the programmer on the kitchen wall, whether its HW, CH or both on/off, the horizontal black indicator lever on the valve is always at the H position.

The CH works perfectly, and if say the CH was off, and you then turned on the HW via the programmer, you would hear a noise, suggesting that the system is responding.

We first thought that limescale had caused the spindle/valve to become stuck - as its hard water area - but after researching the web it seems that the motor or microswitch could be the culprit. Its a new property, was on market for ~ two years before, so HW was barely turned on during that time, only CH.

After researching on web and reading many posts on here, I see that some levers can be moved? I would like to clarify this. So the black horizontal indicator level that points to W,M,H - can that be moved manually, whenever? Does anything need to be done/turned off before attempting it? My draft plan (tell if wrong), is to find a way of alternating the position of the valve, to move it from side to side a few times to try and nudge away any possible limescale etc.

Basically, want to try everything I possibly can to fix the problem before going onto replacing the whole thing altogether, as I hear you cannot replace the head only for this valve model.

Model for ref again:
Mid position valve, ACL Lifestyle, Drayton, 22m, 679H340-3OLO, 380-1687, Model ref MA1/679-3, part no 27101,

Hope resurrecting posts isn't frowned upon

 

[MANDATE]

You have to understand first that that the motor only turns about 2 revolutions from HW position to get to mid position and then another 2 revolutions to get from mid position to CH position where it comes up against a stop. So the motor no longer turns but it is energised to keep it there.
When power is removed from the motor a return spring unwinds the motor back through mid position and back to HW position.
Assuming there is power from the room stat to the white wire of the motor, it should drive the motor over the first half. If it does not then either the motor is at fault or the valve spindle is stuck or too stiff.
The lever provided for a different purpose can be used to force the quadrant/motor but it will only take it to mid position when you really would like it to go to CH.
To get CH only two functions are needed. (a) the valve has to be moved fully across to CH and (b) the boiler has to light.
(a) is dependant on the motor/ spindle stiffness and the wiring to it, while (b) is dependant on one of the micro switches.
This micro switch is not used when when you choose HW only or HW with CH. When HW is involved the boiler gets it's power from the cylinder stat.
Of course as soon as HW becomes satisfied then the power through the cylinder stat stops, the valve moves to CH (if it can) and power is restored through the micro switch.
Also note to be careful if delving into the actuator head. With CH and HW turned off, there is still another wire which remains live from the HW OFF terminal. Unless you remove the power totally

 

[loko2468]

Hey thanks MANDATE for your explanations, taking notes...

The lever provided for a different purpose can be used to force the quadrant/motor but it will only take it to mid position when you really would like it to go to CH.

Did you interpret 'H' as water? If so I'm sorry - I meant that the indicator lever is stuck at the central heating position. What I really want to see is for the indicator lever to be pointing at 'M' or 'W' (midpos/HW). And ideally for that to be automatic!

Again, central heating works perfectly, its just hot water which doesn't respond.

So its fine just to try yanking this indicator lever across? I'll know not to apply too much force, I hear that it shouldn't be loose and that it should be 'springy' like.

Also note to be careful if delving into the actuator head. With CH and HW turned off, there is still another wire which remains live from the HW OFF terminal. Unless you remove the power totally

Noted - although I won't be going near the electrics to start with.

Thanks again...

 

[MANDATE]

The rest position with no power applied is W (HW) and if your valve is at H (CH) with no power applied then it must be stuck there. because the spring should unwind motor and quadrant.
This could be the valve spindle stuck and spring not strong enough to move it back.
With valve stuck at H (CH) the lever will be loose and will have no effect.
It's only when valve is at W (HW) the lever is used to move valve to M (mid) where it can be held/latched (for filling purposes) and in this situation there will be some resistance turning the geared motor against the return spring.
Sounds like the whole valve needs replacing if you can't remove the head