Fairly sure my Drayton ZA5 is duff, does this sound right?

23 Nov 2013
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United Kingdom
Hi Guys,

Got a problem with my heating at the moment in that the boiler is not switching off when the thermostat clicks off.

I think I've pinned it down to the motorised valve, which is a Drayton two-port with a ZA5 actuator. If I move the manual lever then release it the burner clicks off. I can also get it to click off sometimes by altering the thermostat to send on/off signals. After multiple attempts at this it will shut off, sometimes coming back on shortly after.

From what I've read, this sounds like there's something wrong with the actuator and for £40 odd, I thought I'd try fitting a replacement before calling someone out.

Does this sound right?

If so I have a question about fitting. My understanding is the valve is normally closed, and when it switches on, it both opens and tells the boiler to fire up. In the event of the actuator being removed from the valve, the valve would remain closed and the boiler would stay off.

If so, then why do the ZA5 instructions say to move the manual lever to the right before installation. Seems like this would have the actuator set in the open position, but the valve closed?

Many thanks!

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One would normally set the old valve to manual before removing it, then the valve would be ready to accept the new actuator.
And it does sound as though your actuator is the problem, micro switch sticking.
Thanks Mick!

I went to Screwfix yesterday and picked up a replacement actuator, and after debating whether to fit it yet (I have guests tonight and didn't want to risk screwing up and having no heating) I decided to give it a go.

Removed the old one, which practically fell apart in my hands - casing clips broke, one of the springs fell out and the power cord clip snapped - and unwired it. Moving the lever produced no audible click of the microswitch, unlike the new one.

I wired in the new one, flipped the lock lever back to closed and with crossed fingers powered it all back up.

Success! Cycled the heating on and off a couple of times and it seems to be working great. I've probably jinxed it now by saying that!

It's actually better than before as it appears to have solved another problem where the boiler would switch the burner off but not actually power off, it would sit there flashing an error code for "no water flow".

One thing though, when I was fitting the new actuator I could hear a rattle so I opened it up and this spring/clip fell out:


I couldn't see where it went and it seems to be working fine without it. I even dismantled the old one to see if that had one too, but couldn't see it.

Does anyone know where it's come from?
That looks like a contact out of a switch, did it fall out of the box or the actuator itself?
though If your new actuator is working correctly I wouldn't worry about it, it has probably just slipped in there during packing

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It was in the actuator itself, which was a little worrying. It does seem to be working fine now, so possibly got in there by accident, or maybe something to do with the manual lever which therefore wouldn't affect normal usage.

I'm sure if it is required for operation it'll make itself known at the most inopportune time!

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