Failed central heating valve?

[Roger Mills]

ICBW but I thought he'd already confirmed that.

[Davey]

Which post? I missed it if he did. I saw that he said he had a meter available.

[Graeme]

In message , Davey writes

Thanks for all the advice guys. I'm not ignoring you, just waiting for the weather to turn. Seems a pity to be doing indoor stuff on days like today.

[Graeme]

Not yet, but will do.

[Roger Mills]

He's now saying he didn't - so I must have imagined it. I did say ICBW . . .

[ARW]

Normally the sort of job you can do in August:-)

We hit 30 deg today Linconshire

[Graeme]

In message , ARW writes

Even up here in Aberdeenshire we hit 26 which is good for mid summer!

[Graeme]

In message , Davey writes

Right. Removed the whole actuator assembly from the valve, and the valve spindle turns easily. Held the actuator and applied power - I'm assuming the actuator should actuate, but it didn't so either the actuator is dead or there is a wiring problem.

There is indeed a nearby junction box and, within, the four wires from the actuator are connected to a four wire cable which runs to the programmer. The wires within the junction box are all neatly connected and insulated, so cannot get probes in, to test. Would it be OK to cut the wires, remove the four connectors and replace with a chocolate block, which will fit within the junction box?

[Davey]

Personally, I see no problem, but I'm not a qualified electrician! What you describe is how mine is done.

Can you find the other ends of the wires that feed the junction box, at the programmer end, and check the wires for power there? That might find a problem, closer to its actual location. Or maybe test the wires at the actuator?

I reckon at this point that the actuator is probably dead, but it's worth checking as far as possible first, just in case it's not that.

[Roger Mills]

Don't see why not. If - as seems likely - you end up needing to replace the actuator, you'll need to break those connections anyway.

[Graeme]

In message , Davey writes

I went ahead without waiting for a reply. Five wires, not four, one being earth. Anyway, now joined via a choc block and 240v indeed across the brown and blue wires.

Tried applying power whilst the actuator was off the valve, and nothing, so looks like a new actuator. Oh well, at least the wiring connections will be easy, now.

Will report back when actuator purchased and fitted.

[Roger Mills]

If you fancy taking it apart you may find that you only need to replace the motor - obtainable from the likes of Screwfix for about 16 quid.

[Read the reviews for further info.]

[Graeme]

Yes, I had thought about that, but the area just below the motor itself seems stuffed full of little parts ready to ping around the room, never to be seen again. I'll have another look, though. Having got this far ...

[Roger Mills]

I don't think you've got a lot to lose! If you can't mend it, you'll have to buy another actuator anyway, so you may as well see whether you can get the motor out without everything flying apart. [The motor itself comes with a reduction gearbox whose output shaft rotates very slowly - so that will all get replaced. Is that what you mean by little parts?]

Once you've got the motor out, test it by applying power directly to it before buying a new one - in case the fault isn't the motor itself (but it almost certainly is).

[Davey]

Coincidentally, my boiler started to run yesterday, but stopped after a few seconds. It did not run again all evening or night. Today, I started by checking that it did indeed run of the CH was turned on, which it did, so the boiler is ok. Proceeded to do electrical checks, and eventually found that the cylinder 'stat was stuck Off, I had to turn it all the way to max. to make it work. It's now working, but I'll get a replacement. It's now working, but I'll get a replacement, it's clearly not happy any more.

It's not always the valve!

[Graeme]

Interesting. Just removed the motor, and wired it to a 13 amp plug, and it works. Huge torque and slow final output. I couldn't stall it with my fingers. So, replaced motor and tried again, still with just the motor attached to a plug, but not attached to the valve itself. It works.

Put the complete actuator back on the valve, and nothing, yet 240v registered by meter, which tells me something is broken in the electrical 'gubbins' mounted above the valve but below the motor. I imagine there is some sort of micro switch within, which is buggered?

Time to replace?

[Roger Mills]

If it's a 2-port valve - which I believe it is - the only micro-switch should be the one which closes when the valve is fully open. There's not one in the motor circuit - the motor is connected directly to the brown and blue external wires. [You should be able to verify that from the internal connections, having removed and replaced the motor].

So the motor works when you connect the mains directly to it. What I'm not clear about is how you tested it having re-installed the motor. With the motor installed and connected internally, and with the actuator OFF the valve, the motor should run when you connect mains across the brown and blue external wires and should rotate the internals against the return spring to the 'valve open' position, and the motor should then stall.

What actually happens when you do that?

Are the internals free to move? If, with no power applied, you move the manual lever to the 'open' position, can you feel some resistance, and hear the gears whirling? When you let go of the lever, does the spring move it all back to the closed position?

[Graeme]

In message , Roger Mills writes

Back to basics. The motor, when removed from the actuator assembly, works perfectly when connected to an ordinary domestic 13 amp plug. Plenty of torque - I cannot stop it turning, with my fingers.

The valve stem, with actuator assembly removed, turns easily with fingers. The radiators then work with another zone calling for heat.

Looking at another zone valve, the wiring is correct.

There is a five core cable (including earth) from the programmer to the zone valve. Using a meter, there is 240v across the brown/blue, whether or not the programmer is on (calling for heat) or not BUT the motor, hanging loose from the actuator head, does not turn whether or not the programmer is on.

There is a little micro switch within the actuator - pressing that in with a screwdriver blade causes the oil fired non combi boiler to fire, even if the programmer is off. However, clicking the micro switch in does not power the motor, whether or not the programmer is on or off.

Ignoring the earth, the wiring is thus :

Four cores from the programmer to the junction box. Blue, brown, black and second black.

Another four cores from the junction box to the actuator. Blue, brown, grey and orange.

They are connected at the junction box :

From To programmer Actuator

Black Brown

Black Orange

Brown Grey

Blue Blue

The brown and blue wires on the actuator side connect to the motor, so not connected directly to the incoming 240v (brown/blue) from the programmer.

However, there is something else odd. Looking at another actuator, when the motor runs, a little tab moves and presses the micro switch to fire the boiler, but on the defective actuator, the tab does not move far enough to press the micro switch, when using the manual lever. Something has 'slipped'?

I suppose next stage should be to swap actuators.

[Davey]

That is normal, manual operation does not usually operate the switch.

[Graeme]

In message , Davey writes

Ah! OK, thanks.