Drayton valve 'sticking'

[Paul Drawmer]

S plan system. One of the two port valves is sticking. The valves are only about 4 years old.

What happens is the CH gets up to temp, 'stat switches off, but system still runs.

First found out when I came home and realised that the CH pump was running whilst boiler was off, and the timer was past the all off time for the night.

If I tap wallop the valve cover, it switches off, all is fine and it returns to normal operation next time the stat calls for heat. I don't know if the boiler switches off due to over heat, or if the boiler is switched off by the 'stat.

Is this a body or motor problem? Are the motor units user serviceable?

[Paul Drawmer]

Having photographed the cover in a mirror(!) it's a ZA5

[Paul Drawmer]

OK - thanks folks. I'll do a top swap on it then.

[Paul Drawmer]

Update. Replaced actuator only this morning. Oddly enough, the valve body inc actuator is cheaper than actuator only - mad.
swapped the tops over, replaced the new wires one by one for the old one, control restored. Thanks PH for the info.

[Paul Drawmer]

UPDATE. Grrrr. it's doing it again. CH pump running and boiler cycling even though all controls are calling 'off'.

Haven't got round to tapping each valve to see which one isn't switching off yet. And I remember getting to the wiring centre is an arse. And I'm stiffer now than I was at 69! May have to pay someone this time.

[Paul Drawmer]

Gary C said:

Just replaced the microswitch in our ZA6.

They get sticky but are an off the shelf part if your that way inclined. At £3, a lot cheaper than a £70 new head. Fairly simple solder job but make sure you dont loose the springs. Also these bodies age, the plastic cracks and the springs detach, you can hook them back through the holes in the body where the hooks for the springs sit.

https://uk.rs-online.com/web/p/micro-switches/1616...

Edited by Gary C on Saturday 19th November 10:11

That's interesting, thank you.

[Paul Drawmer]

Lincsls1 said:

So it seems you have mistakenly diagnosed the wrong head as the one keeping the system running.
Either get another new actuator and replace the other one, or if you've got the old one, put that on.
What the boiler out of interest?

I got it right last time, but need diagnostic help this time. How do I tell which of the two valves in the airing cupboard is at fault? Last time, a sharp tap on the errant valve cover would make it switch. This time that doesn't work. I've tried manually activating the valves but that's not making it switch off.

So, is the only way to get into the rats nest and sort out which is live when it shouldn't be?