Drayton MA-1 valve problem.

[skywatch99]

Hi all!

Had no heating the other morning. Boiler runs fine and I found that the HW was hot.

Seems that the ma-1 valve is not moving to the CH position. Putting it manually into CH got the house warm (so boiler/thermostat/wiring OK). The spindle in the pipe moves freely so not a locked up valve. The valve head manual override moves freely with the usual whirring sound.

I took off the head and made all for CH and no movement from the valve head. So I took the head apart.

Springs are still working and anchored correctly. That's good!

The motor reads 2500ohms approx, so not open circuit.

Anyone with any experience of these have any insight?

Thanks

 

[skywatch99]

Just an update - I put the head back together again and the problem is still there - ie, CH call for heat = no movement on the valve head. BUT.... if I give it a nudge towards the mid position the motor 'kicks in' and takes it all the way to H. Now we have heat, but what is likely stopping this from happening automatically as it should? I have to admit I am a little baffled at the moment by this!

 

[heatservice]

Have you got a 230 volt supply to the synchonous motor when you select CH, if you have and the motor doesn't drive over then a new motor is reqd, always check with a multimeter.

 

[skywatch99]

Thanks for the hint.

See my update (probably crossed with your post) - power is available or the motor wouldn't move when nudged. Motor measures 2500ohm, is this normal? (I have one other old motor and that is about the same, so assuming it is normal).

What puzzles me is the changeover microswitch does not seem to be pressed at any point when the head is apart, so does moving the manual override somehow compensate for this? The microswitch works correctly when pressed with a screwdriver.

 

[heatservice]

Im not too sure about the resistance reading but I have seen many of those motors either get too weak to overcome the strength of the springs without giving them a nudge or even stalling after getting warm, have you tried your spare motor as it only takes a few minutes to change, one other thing, the round motor cover can be removed allowing you to rotate it by hand to its maximum position to see if it triggers the microswitch

 

[skywatch99]

Good idea - but it got really cold so I have to have it manually working for now - will try again tomorrow.

As I test I got HW working and then put on CH - no movement in the valve. Then I turned off HW and cycled CH off, then on again. Still no movement of the valve. But as soon as I manually moved it to mid-position, the motor took over and moved it all the way to CH, where it remains giving us some welcome heat!

I am siding towards the motor going bad and being too weak now to get out of hw position without some external help. But that is only a hunch.

I'll try the other motor (out of a previous failed drayton valve) and see what happens. The 'old' valve was leaking water into the actuator body and shorting out the electrics and tripping the breaker, that took a while to figure out I can tell you as it only leaked on occasion and only while turning!

 

[fixitflav]

Thanks for the hint.

See my update (probably crossed with your post) - power is available or the motor wouldn't move when nudged. Motor measures 2500ohm, is this normal? (I have one other old motor and that is about the same, so assuming it is normal).

What puzzles me is the changeover microswitch does not seem to be pressed at any point when the head is apart, so does moving the manual override somehow compensate for this? The microswitch works correctly when pressed with a screwdriver.

There was a long thread started by ericmark on 24 March entitled Thermostat N/O or N/C is N/O ever used? Most of it irrelevant to your problem, but it says your 2500 ohms is about right.

 

[skywatch99]

Thanks for reply about motor windings, now I am confused again!

I have edited my first post as I realised a mistaken assumption on my part had given me the wrong idea as to the problem.

So in a nutshell I have the situation where at power on the diverter is in W.

Turn on W and call for HW and the pump and boiler start, all is well at this point.

Turn on CH and call for CH and the valve remains in W. Not good.

Turn off HW and valve remains in W. Not good.

Manually move valve to mid positon and it continues to H. Good (but shouldn't require the manual intervention).

Turn on W and call for HW, valve moves to M. Good.

Turn off CH and valve moves to W. Good.

So now I am confused as to what is happening. I will try an old motor in it next to see if it makes any difference.

 

[stem]

Turn on W and call for HW and the pump and boiler start, all is well at this point.

That's fine. When not powered, the valve sits in the W position where it is held by a spring. At this point the boiler is turned on and off by the hot water cylinder thermostat when hot water is / is not required.

Turn on CH and call for CH and the valve remains in W. Not good.

Indeed, not good. At this point the room thermostat should have made the valves white wire live, and the motor will start to operate, winding the valve away from the hot water only position. If it doesn't there could be 5 possible reasons that I can think of for this:

1. There is not a 'live' on the white wire coming from the room thermostat
2. The motor has failed.
3. The motor is too weak to move the mechanism.
4. The mechanism is stiff so that the motor is not able to move it.
5. The first internal microswitch inside the motorised valve that is operated just before the mid position has failed or is sticking. (this is the one connected to the grey and white wires)

From your comments it would appear that 1 and 2 can be ruled out as the motor will hold the valve in the heating position, and so can 4 as the mechanism seems to be moving freely.

Turn off HW and valve remains in W. Not good.

Not necessarily wrong. If heating is not required either at this point. The valve will return to the W position because of being pulled there by the spring. The Hot water won't come on at this point because the cylinder thermostat isn't telling the boiler to operate.

Manually move valve to mid positon and it continues to H. Good (but shouldn't require the manual intervention).

That would happen if the first microswitch was stuck in one of its positions. (linking the motor to the grey wire)

Turn on W and call for HW, valve moves to M. Good.

That would happen if the first microswitch was stuck in one of its positions. (linking the motor to the grey wire)

Turn off CH and valve moves to W. Good.

That's as it should be, motor not powered valve pulled to rest position by the spring.

Sounding like microswitch number 1 to me.

 

[heatservice]

My money is on a weak motor, we will find out when you have fitted your spare one.

 

[stem]

It's quite possible, and I didn't cross it off my list.

My thinking was that if it's able to wind from 'centre' position to 'heating only' against the maximum force of the spring as it's fully extended, it must be providing a reasonable amount of force. On the other hand, if the microswitch was sticking and the hot water was also required at the same time, the motor would only be getting the rectified DC that is used to hold it in the mid position, which is not enough to move it.

I would certainly try changing the motor first just in case, if it is the switch that means a new valve.

The problem with these valves is the multiple permutations that are possible, create different scenarios. When heating is required it makes a difference if hot water is, or isn't required at the same time.

Going for a lie down in a darkened room now.

 

[heatservice]

Have seen it so many times where motor appears dead so you lock it in man position to get heat with HW only for the motor to temporarily come back to life and unlock itself from man position before dying again. The manufacturers could go back to the old ways and wire then so if there is no demand for heat they return to the unpowered HW position
but instead if heating is being called for last thing at night and the programmer switches off the valve remains in the powered stalled CH position all night long, it called planned obsolesance.

 

[stem]

I'm surprised that the energy efficiency police haven't latched on to the fact that millions of motorised valves up and down the country have their motors permanently powered to hold them in the heating position, and that under certain conditions they will even do that even when the central heating has gone off.

 

[skywatch99]

Thank you all for your input, especially on a Bank Holiday weekend...

I have put the 'spare' motor on and no change, so either I have 2 bad motors or it is something else. I do now know that there is *NO* 230V to the motor (across the orange wires) when I call for CH. The thermostat seems to be calling and it 'clicks' and the ch on is selected at the controller. All I get is about 7-8V AC. So making progress with this.

I have tested the microswitches and I have seen the problem I think

The microswitch that goes to the motor from the grey wire is connecting grey to the motor when pressed in. But, it does not connect to the white when it is released. So mechanically it is switching, could the contacts on the inside have burnt out or failed? Seems likely now.

If it is this, should the pcb just lift out? It seems to be stuck in one corner and maybe they glue this in the factory but I can't see any glue?

Thanks

 

[stem]

I have tested the microswitches and all are working

By testing the microswitch, do you mean that you have used a multimeter to check, that when the valve is 'stuck' in the W position, but the CH is calling for heat, that the microswitch is actually electrically connecting the motor to the white wire? (both the white wire and the live wire to the motor should be at 230V) Physically hearing a 'click' does not necessarily mean that it is working as it should inside, and is actually making an electrical connection.

The orange wire from the second microswitch is there to provide a 'live' to operate the boiler when the 'central heating only' is selected (it takes over from the cylinder stat which has this function for 'hot water only' and 'hot water and heating' positions). The orange wire is connected to the white wire by the second microswitch, to provide this boiler control signal but it does not have any effect on the actual positioning of the valve.

However, this second microswitch which the orange wire is connected to, is responsible for holding it in the mid position but this seems to be working OK.