Potterton Motorised Valve

[KevinLynn]

Help! Recently i had a problem with the Potterton motorised valve (type MPE322 - 3port) fitted in my central heating system. The hot water would work OK but the valve would not motor open to switch on the central heating...........SO.......I replaced the actuator with the identical model, carefully wired it up as the old 1 - and switched it all back on.

Bingo! Everything is working fine - the valve is happily motoring to each position - execept for 1 small problem - when I have Heating only on and it switches off (either via the thermostat or controller) - the valve should Spring back to close the heating port with heating off (port B hot water port open only) right???

But mine doesn't - it stays in the Heating port open only position - and if i listen i can hear the actuator humming as its power to open right? Maybe my old valve had this problem and thats why it burnt out - i'm guessing the valves ain't designed to be powered on all the time.......

So can anyone help me and point me in the right direction - I figure this is an electrical wiring problem - but where and how to start checking thro the system?? The junction box is a mass of terminals and wires and not marked - i feel fairly comfortable sorting out electrics if someone could point me in the right direction - things it might be - sequence to check the circuits in, etc,etc..........

If you need more info please let me know.
I'll be very grateful if i can get help to sort this - and so would the g/f who's fed up with talk of valves and heating

Thanks!!!!!

 

[breezer]

you say the old one failed, now you know why. I should say that as you have wired it the same as the old one, you are now seeing why the old one burnt out, i think it is the valve that is stuck, so the motor is trying to turn it to where it should be (which is why you can still hear it) but as its the valve at fault the motor can not turn it to the correct position and so it too will burn out.

then again i could be wrong

 

[KevinLynn]

I checked the mechanical valve and its free to turn easily by hand - thats why i think its the electrical wiring somehow - even with everything switched off, the valve is still receiving power.

Yes i wired it same as the old one........so yes i guess this one will go the same way unless i sort it..........

Help

 

[ollski]

surely there was a wiring diagram with the actuator?, if not then on their website. The wiring is basically just following the common and switched lives along their logical route. Sounds like you probably have a grey or white wire from the motor into a permanent live....good luck!!

 

[GreenDave]

Hi there . Did you eventually track down a circuit diagram or did you suss out the knitting? I too have a Potterton MVS322 which is stuck in one position (half CH/HW), despite selecting CH only or HW only. First inclination is to replace the controller but it would be nice to confirm it's been wired correctly.
Any one else got any circuit diagram?

 

[MANDATE]

If it's been working ok I'd say it was wired correctly.
However. switched live from room stat feeds white wire of valve.
wire from satisfied terminal of cylinder stat feeds grey wire of valve.
wire from HW OFF terminal of programmer feeds same grey above.
Orange wire from valve feeds boiler/pump, which is also fed from 'not satisfied' terminal of cylinder stat.
Blue wire is ' neutral'
Green/yellow is earth.
If valve is stuck at mid point. I would be looking for (a) broken return spring (b) stiff valve spindle or most likely broken/faulty gears on valve motor, preventing quadrant from returning to HW position.
How did you verify it was stuck at mid point?

 

[GreenDave]

I've just read your e-mail having replaced with a new Potterton Myson ACT322 Actuator from Heating Controls Online (£36.90 inc VAT) today.

Previously the recess hole that takes the spindle from the valve body (which in turn moves the valve) wouldn't move electronically when HW or CH or both were selected so I figured the control valve was definitely faulty. The wiring diagram that came with the new control valve confirmed wiring was going to the right places (even though it looked like a tangle mess!). Once fitted, when I selected CH only, the CH light came on, repeated for HW only - HW light came on, then for both CH/HW when both lights came on (as did the pump & boiler).

I was able to examine the recess in which the value spindle normally goes by separating the the pipe work from the valve body (or actuator) via the two mounting screws. When HW, then CH, then HW+CH were selected it slowly turned the mounting hole to the correct positions....yippee - no more central heating in the summer - just hot water!!

It had been working before, but for some time it would only run up CH when HW was switched on. Now it runs both independently. So I have got HW/CH that are electrically independently runnable AND no stuck valve.

Thanks for your comments. If you need a diag I can scan the one I've got.

 

[MANDATE]

Glad to hear you've got it sorted. Did you find out how it came to be stuck at mid point.
You see it basically starts in the HW position and the motor operates a geared quadrant when power is applied to the motor through the white wire to get valve to mid point. When this power is removed a spring turns the quadrant and motor back to HW position.
Most problems seem to be related to either the motor not being strong enough to overcome the return spring. Or if it does operate correctly a faulty micro switch stops power going to boiler in CH only position.
If the demand is for HW only or HW and CH the boiler receives the power from the cylinder stat.

 

[outinthestix]

The valve in a y-plan does stay powered in the last position selected. Thats why the motors burn out. It's normal. Just don't listen to it and relax.

 

[MANDATE]

So if last position selected is HW and CH together and valve is in mid position when both are switched off at the same time you say valve stays powered in mid position. Can you explain how it does that? cause I can't agree.
CH only yes! HW only yes! but the valve/motor aint powered up.
HW and CH No!

 

[outinthestix]

You are right Mandate but the OP said when he has the CH on. In that case we are both agreed the motor still is powered even after the CH is switched off.