Very unusual problem with Drayton MA1

[Thedagger]

Have a MA1 that works well in that when CH calls it moves across and delivers this as expected and when HW calls it moves across and delivers this perfectly, so spindle isn't sticking and general mechanics seem fine
BUT
It doesnt ever allow both CH AND HW at same time when both are calling for it and move to the mid point ???
it just prioritises HW in this scenario and is doing my head in as no heating can happen whilst the HW is doing it's thing

Hopefully someone may have come across this before?

TIA

 

[Simon F]

welcome to the forum.

Is this a change to how it has worked before?

 

[IDCHAPPY]

I thought 3 ports, if wired correctly prioritized the HW... I'm semi pished though so maybe speaking nonsense

 

[Thedagger]

welcome to the forum.

Is this a change to how it has worked before?

No it's always been like this but getting on our nerves now :disappointed:

 

[doitmyself]

Is the valve installed the correct way round? Port A to the rads, port B to the cylinder.

 

[LPC]

welcome to the forum.

Is this a change to how it has worked before?

This is the important question. If it has always done this/you've only ever known it to do this, then the system is likely wired incorrectly.

If it has started doing this recently, it's the sort of thing you'd be better getting an engineer in to look at then spend a very long time on a forum trying to solve.

 

[Thedagger]

This is the important question. If it has always done this/you've only ever known it to do this, then the system is likely wired incorrectly.

If it has started doing this recently, it's the sort of thing you'd be better getting an engineer in to look at then spend a very long time on a forum trying to solve.

Yes its ALWAYS been like this - would buying a new actuator mean it would just work properly or do I need to look at the wiring - someone mentioned something about the white wire ???

 

[LPC]

Well, i'd be checking the wiring first in that case. But a 3-port valve would only set you back ~£50 and they're relatively easy to fit. I generally change the body too but you could try just changing the head as MA1s are readily available.

Check your wiring against this:

 

[doitmyself]

Well, i'd be checking the wiring first in that case.

The wiring shown assumes that the valve has been installed correctly - Port A to rads, Port B to cylinder. As the problem has always existed the orientation of the valve also needs to be checked. I suggested this earlier, but it seems to have been ignored.

 

[mountainman]

If it has always been like this then perhaps the wiring is configured for the old BG 'guaranteed warmth' system.
This prioritised hot water and the heating wouldn't comes on until the hw was satisfied.

 

[LPC]

The wiring shown assumes that the valve has been installed correctly.

Which is exactly why I said he should check the wiring against that picture to see if it is installed correctly.

 

[Thedagger]

The wiring shown assumes that the valve has been installed correctly - Port A to rads, Port B to cylinder. As the problem has always existed the orientation of the valve also needs to be checked. I suggested this earlier, but it seems to have been ignored.

Sorry didnt purposely ignore you - just checked now and it appears valve is installed correctly as port A definitely goes to rads as you described

 

[doitmyself]

Which is exactly why I said he should check the wiring against that picture to see if it is installed correctly.

I'm not disagreeing with you, just pointing out that the physical installation of the valve, i.e it's the correct way round, needs to be checked as well.

 

[Anton]

The Drayton MA1 is a mid-position diverter valve. When calling for both hot water and heating, providing it is wired correctly, the valve would be held in mid-position by what's called a DC brake.
(Applying DC voltage to the actuator motor locks the motor in position). This is done via micro switches in the actuator. If it's always mis-behaved then it sounds like the system is not wired correctly. 240 volts ac to the orange wire and the white wire to the actuator at the same time, should hold the valve in mid-position.
Also check where the grey wire is wired to, 240 v ac to this wire closes the hot water port.

 

[Thedagger]

thank you everyone, I am seeing your advice and replying but because my replies have to go to a moderator first - you don't see my response for sometimes hours/days

Thanks for all your help though