actuator

[ssb1973]

Hello,

Hope you can help.

I believe my MPE222 potterton actuator is faulty, I've detached it from the valve. When I turn up stat, the motor whirrs slowly to switch heating on (good), however, when I turn stat down the springs whirrs back quickly back to the open position instead of closed. - (Open is valve lever vertical position, closed is valve horizontal position).

This has caused the heating to be on all the time, no matter whether the programmer is on or stat is turned down. The only way of turning it down, is to turn down the temperature on the system boiler.

I can manually turn the valve by hand to turn the heating off, but then every 15 minutes or so, the Vaillant Thermocompact, switches on for 1 second, then goes off, then goes into water pump overrun status (is this normal behaviour, as I believe the faulty actuator may be sending signals to the boiler, even though the actuator is detached from the valve?).

My question is, if I buy a new actuator ACT 222, will this be calibrated so that off is horizontal, and closed is vertical postion of the valve?

From other posts I've read, it's easy to change an actuator, it'd be a first for me, I understand that, I turn off the mains, unscrew existing, re-attach wires to new one as per old one, re-attach to valve, and Bobs your uncle.

The Corgi person who serviced my boiler who diagnosed this problem as the actuator, said if I buy the actuator, he can fit it for £50.

 

[D_Hailsham]

I believe my MPE222 potterton actuator is faulty,

Here are the Instructions for the MPE222.

The valve has four wires: Brown and Blue are the motor connections - brown goes live when the thermostat calls for heat and makes the motor run; Grey is a permanent live and Orange is a switched live to turn the boiler on - there is an auxiliary switch in the actuator which closes when the valve opens and connects Grey to Orange.

when I turn stat down the springs whirrs back quickly back to the open position instead of closed. - (Open is valve lever vertical position, closed is valve horizontal position).

Are you saying that the connector which links actuator to valve spindle in the actuator rotates 180 degrees when the power is removed from the motor? You will find that the spindle in the valve body can only rotate a few degrees from closed to open - try it and see. I suspect that the spring is made fairly strong to ensure that the valve closes properly. When the motor is energised it will turn the spindle until it is fully open; the motor then stalls. Testing with the actuator removed from the body will give a false indication.

I suspect that the auxiliary switch in the actuator is faulty. Replace actuator on valve body and then disconnect the grey wire. When you turn the thermostat up the motor will run and open the valve but the boiler should not fire.

From other posts I've read, it's easy to change an actuator, it'd be a first for me, I understand that, I turn off the mains, unscrew existing, re-attach wires to new one as per old one, re-attach to valve, and Bobs your uncle.

Correct. You already know how to remove the actuator, so its just a case of changing one wire at a time to make sure you don't get the wiring wrong.

The Corgi person who serviced my boiler who diagnosed this problem as the actuator, said if I buy the actuator, he can fit it for £50.

Waste of £50 - DIY

 

[ssb1973]

Quote:
when I turn stat down the springs whirrs back quickly back to the open position instead of closed. - (Open is valve lever vertical position, closed is valve horizontal position).

D_Hailsham wrote

Are you saying that the connector which links actuator to valve spindle in the actuator rotates 180 degrees when the power is removed from the motor?

no, I have not removed the power from the motor yet, when the room stat is turned up, the motor in the actuator spins slowly more than 180 degrees, when the stat is turned down, the motor spins fast more than 180 degrees, maybe 360. All this is while the actuator is detached from the metal plate, and still has power.

You will find that the spindle in the valve body can only rotate a few degrees from closed to open - try it and see.

The spindle can turn more than 180 degrees, but to turn the CH off I turn it 45 degrees left or right to switch heating on (spindle vertical), or 45 degrees left or right to switch heating off (spindle horizontal), just like you would turn a key in a keyhole.

Thanks D.

 

[D_Hailsham]

Are you saying that the connector which links actuator to valve spindle in the actuator rotates 180 degrees when the power is removed from the motor?

no, I have not removed the power from the motor yet, when the room stat is turned up, the motor in the actuator spins slowly more than 180 degrees, when the stat is turned down, the motor spins fast more than 180 degrees, maybe 360. All this is while the actuator is detached from the metal plate, and still has power.

Turning the stat UP applies power to the motor; turning the stat DOWN removes the power from the motor. So the spring alone is responsible for the motor spinning fast.

You will find that the spindle in the valve body can only rotate a few degrees from closed to open - try it and see.

The spindle can turn more than 180 degrees, but to turn the CH off I turn it 45 degrees left or right to switch heating on (spindle vertical), or 45 degrees left or right to switch heating off (spindle horizontal), just like you would turn a key in a keyhole.

These valves use a "shoe" to act as the valve, I was thinking of the Honeywell valves which use a rubber ball. There are 90 degrees between vertical and horizontal; where do you get 45 degrees from?

 

[ssb1973]

sorry, you're right, it's 90 degrees not 45. It's been a while since I've been to a maths class

 

[D_Hailsham]

sorry, you're right, it's 90 degrees not 45. It's been a while since I've been to a maths class

Tempus fugit.

Rereading your original question, it looks as if the auxiliary switch has stuck with the contacts permanently closed. This would mean that power was continually being applied to the boiler, even when the valve was closed. You can check this by disconnecting the grey wire (TURN POWER OFF FIRST). The valve should open/close when the stat is turned up/down but the boier should not light.

You may be able to clean the switch contacts, if not - it's a new actuator.

 

[ssb1973]

Thanks for your help everyone, I bought an act222 actuator for around £34, and fitted it myself, all is working now normally.