Confusing Drayton MA1 Actuator fault

[elsmandino]

Hi there.

I woke up the other morning and realised that my central heating was not on as expected.

The acutator should have been in the middle position to feed both the hot water tank and the central heating - however, it was in the water only position (to the right), despite the thermostat trying to get the central heating up to temperature.

I did some testing and here is what is happening:

With no water tank or central heating request, the acutator stays in the W position.

If I turn the heating on, nothing happens.

If I turn both the heating and water on and manually move the acuator to the M position, it stays there.

If I turn just the heating on and manually move the actuator to the M position, it automatically moves to the H position.

When in the H position, if I turn the heating off, it automatically returns to H.

When in the H position, if I turn the heating off but leave the hot water on, it automatically returns to M.

Really weird - in light of the above, the motor seems to be working. I even popped to Screwfix for a replacement but have the same issue.

The problem, therefore, is the default W position - the motor seems to get no signal to move when it is in that position only.

Any advice on how to potentially fix would be greatly appreciated, or am I looking at a whole new unit?

 

[CBW]

Have you changed anything recently, eg programmer? If not, then it’s likely going to need a new actuator.

 

[terryplumb]

Does the boiler fire up in any of the valve positions ?
The motorised valve returns to domestic hot water position by spring pressure ,its default position.

 

[elsmandino]

Yes - if the thermostat is set high and the boiler is low on water, the boiler will fire up in all three positions.

No changes at all, unfortunately, just stopped working suddenly one morning a few days ago.

 

[terryplumb]

When in the H position, if I turn the heating off, it automatically returns to H.

This doesn't make much sense ?

 

[terryplumb]

What Exactly is not working , I am a bit confused ??

 

[elsmandino]

This doesn't make much sense ?

Sorry - I meant to say that if the heating only is on and then turned off, the actuator automatically returns to the default position of W.

Ultimately, the only thing that does not work is getting the acutator to move from the default water position. Once it is in the middle or on heating only, it works fine until it is back on water only again and then nothing. The only way I can get it to the middle is manually with the lever.

 

[oilhead]

Replace the actuator. These are probably the least reliable unit.