2 port valve gets stuck halfway

dmc88

Hi

Standard Drayton 2 port Central heating actuator keeps getting stuck between the A and B positions when demand for Central heating drops off, so the heating stays circulating on. Was working fine until a few weeks ago. Already replaced the synchronous motor and it was fine for a week or so but now it's playing up again. The brass valve itself looks newer than the surrounding pipework, turning the spindle with a pair of molegrips is easy, no real resistance.

Any ideas?

Jeepers_Creepers

Hopefully you don't actually need molegrips to turn the valve spindle, but just a firm grip?! And does it feel smooth throughout the arc of movement, and stop at each end with a firm 'thunk'? If so, the valve itself is almost certainly fine.

With the motorhead off, how does it behave - does it whirrr smoothly and cleanly from one end to t'other and return smoothly too?

It does sort of point towards knackered gears - which it only thing you haven't tested/changed

molerat

You should be able to turn a Drayton with bare fingers.

dmc88

So I'm no plumber... The valve spindle is too short to get my fingers on it to grip and turn it and usually too hot to touch, however just got up early to give it a go while the system is cold. I can open and close the valve with my fingers, it isn't easy, but I have delicate keyboard fingers, not manly tradesman hands!
When I have the motorised head off, it displays a full range of motion when I click the central heating on and off (the little black bit the spindle sits in goes fully horizontal for closed and sort of 45 degrees for open, corresponding to the range of movement on the valve spindle). It's slow but it gets there, smoothly. It's just on the return/close when attached it gets stuck half way, like it runs out of 'puff' and gives up?

Jeepers_Creepers

Ach, keyboard fingers are much better than sausages overall

If you can move the actual valve spindle across its full arc, and it's pretty smooth throughout, then almost certainly the valve part is just fine. And almost certainly the gearbox is the faulty part.

To replace the whole head is easier than replacing just the motor - all you need to do is to swap each wire one at a time. Also the head is cheaper than the whole part.*

POWER OFF FULLY at the boiler isolating switch. Open the wiring centre, test each terminal for voltage tobesuretobesure, and then take some clear photos of the wiring just in case.

Cut each of the five wires from the valve a couple of inches from their terminal connectors. This way, the colour of each wire is still there as a guide. Now replace each one in turn, following the colours. Jobbie jobbed.

*Have a look on eBay - you might get a whole new valve for the price of just the head from a merchant. If so, keep the valve body in the cupboard for a plumber to swap whenever the system is next drained down.

dmc88

Just to be clear, do you mean replace the whole plastic box?
https://www.screwfix.com/p/drayton-za6-6-wire-motorised-valve-actuator/5474r

Jeepers_Creepers

Yes.

You've already replaced the motor inside, haven't you - a far more challenging job!

https://www.wickes.co.uk/Drayton-22mm-2-Port-Zone-Valve-BGMVSP-2/p/228404# (Keep the valve body nearby in the cupboard)

Jeepers_Creepers

Seems to be the same as a ZA5?

https://www.ebay.co.uk/itm/DRAYTON-2-PORT-ZA5-ACTUATOR-ZA5-679-2-22mm-VALVE-BRITISH-GAS-BGMVSP2-5-WIRE/232949465188?epid=11034357205&hash=item363cdec064:g:irEAAOSwi-dbs1Jx

dmc88

That's the exact one I bought off eBay Jeepers before you responded lol! Great minds...

Typically, as soon as I ordered it, the in situ unit has begun working again mysteriously. Guessing these are just normal symptoms of it giving up the ghost some time in the future

Thanks for all your help

Jeepers_Creepers

Ha-ha! Ain't that the way.

You've done the trickiest parts of the job already, so when you do come to replace it, just cut the power completely, remove each wire in turn, and fit the new - again in turn. (Or snip the wires to leave a tell-tale coloured sleeve).

If you can wire a plug - and I suspect strongly you can - you can swap this motor.

Don't let Fez' catch you doing it tho'...

Ibrahim5

I remember having problems with a 2 port valve. I took it off. "Just going to B&Q to get one of these. Only £50" I told the wife. "Why can't you fix it?" "I am fixing it". "No why can't you fix that box instead of buying a new one." I took it apart with security bits and found that the microswitch inside was broken. I hadn't realised a microswitch was a standard item and I got one from Maplin for 99p (before Maplin shut down). Soldered it in and it worked fine. One of my cheapest ever repairs.