CH/HW motorised valve replacement

TMSG

We have a Drayton MA1 mid position valve, switching between CH or HW or both. This one is about a year old and doesn't switch anymore between HW and CH (it'll go from HW to CH but not the other way round). The one before, same model, worked for 10+ years but it seems these things are not very reliable...

So I am now thinking of switching to something more reliable. As we do not really need a three-way valve (as there's never any overlap between HW and CH) what would be the best option for replacement?

Thanks for some hints!

Lorian

Dont overlook the possibility of overlapping perhaps setting the water to come on in a period where radiator TRVs may start to back off after initial daily heating.  The HW load may help keep the return temperature low enough to keep the boiler efficiently condensing.

As for valves I recall mine is a Honeywell and is 25 years old, on motor #3 though.

ThisIsWeird

TMSG said:

We have a Drayton MA1 mid position valve, switching between CH or HW or both. This one is about a year old and doesn't switch anymore between HW and CH (it'll go from HW to CH but not the other way round). The one before, same model, worked for 10+ years but it seems these things are not very reliable...

So I am now thinking of switching to something more reliable. As we do not really need a three-way valve (as there's never any overlap between HW and CH) what would be the best option for replacement?

Thanks for some hints!

Remove the motor head - the 'actuator'. Check that the actual valve spindle moves freely - smooth, and with a firm thunk at each end.
With the power off, move the manual lever full distance - does it whirrrr smoothly both ways?
Then try running it via the programmer to see if it moves as expected (leave the actual valve in mid position). Does the head do everything it should? Full move to CH? Return to DHW? Stop midway when coming from both directions?
Anyhoo, when it comes to an alternative, I can't see any way to fit anything other than a similar 3-port valve in that space. Unless you go for the superior 2 of 2-porters (S-plan).

QrizB

TMSG said:

We have a Drayton MA1 mid position valve, switching between CH or HW or both. This one is about a year old and doesn't switch anymore between HW and CH (it'll go from HW to CH but not the other way round).

The valve is only motorised in one direction, the return is via a spring. Unfortunately I don't recall which is which!

I guess you could replace it with a t-piece and a pair of individual valves, if there's room in your plumbing. It'll cost a bit more than a three way valve but should be more reliable.

ThisIsWeird

QrizB said:

TMSG said:

We have a Drayton MA1 mid position valve, switching between CH or HW or both. This one is about a year old and doesn't switch anymore between HW and CH (it'll go from HW to CH but not the other way round).

The valve is only motorised in one direction, the return is via a spring. Unfortunately I don't recall which is which!

I guess you could replace it with a t-piece and a pair of individual valves, if there's room in your plumbing. It'll cost a bit more than a three way valve but should be more reliable.

Good point. If it powers to position 'A' - CH - but doesn't return to 'B' when CH is turned off, or DHW is selected, or when the power is cut to the boiler, then a failed return spring sounds plausible, and could even be a simple fix.
The head comes off with just a push button, I understand. 
But also check the manual lever, which will set it to mid position. 
De-energised, it should be at port B, the HW side. 
https://www.draytoncontrols.co.uk/product/motorised-valve-mid-position

TMSG

Thanks all for the input, I really appreciate it. Perhaps to clarify:

a) we do not have a combi or condensing boiler. HW is kept in good-quality storage tank in airing cupboard.
b) the HW comes on at 7am, when we're still listening to BBCR4 in bed and runs for 15min in summer, 20min in winter. Most of the HW is used in the morning and we never need to heat HW again.
c) the CH switches on at 7.30am, in time for us to get up. In 25+ years in that property HW has perhaps once or twice been running in the evening.

As I wrote, after the switch on the valve has been moved manually to HW it returns on its own to CH once the HW is finished. So just the CH -> HW direction doesn't work.

I've played around a little with the switch when the HW comes on, but the switch is still at CH only. A little nudge will make it move on its own to mid pos but it stops there (CH is off at the programmer). To get it to HW only, I have to move it all the way. This is smooth and makes a whirring sound but it won't move on its own. HTH for diagnosing :-)

ThisIsWeird

TMSG said:

Thanks all for the input, I really appreciate it. Perhaps to clarify:

a) we do not have a combi or condensing boiler. HW is kept in good-quality storage tank in airing cupboard.
b) the HW comes on at 7am, when we're still listening to BBCR4 in bed and runs for 15min in summer, 20min in winter. Most of the HW is used in the morning and we never need to heat HW again.
c) the CH switches on at 7.30am, in time for us to get up. In 25+ years in that property HW has perhaps once or twice been running in the evening.

As I wrote, after the switch on the valve has been moved manually to HW it returns on its own to CH once the HW is finished. So just the CH -> HW direction doesn't work.

I've played around a little with the switch when the HW comes on, but the switch is still at CH only. A little nudge will make it move on its own to mid pos but it stops there (CH is off at the programmer). To get it to HW only, I have to move it all the way. This is smooth and makes a whirring sound but it won't move on its own. HTH for diagnosing :-)

Well, the key thing to take from all this is, YOU LISTEN TO BBC R4 IN BED! Awesome!

cough

It sounds as tho' it's either that the actuator is faulty, or the valve under it is sticky. The MA1 appears to be easier than most to have its head removed to test both options.

https://www.draytoncontrols.co.uk/sites/default/files/22mm (I. Guide).pdf

"Before the actuator is fitted to the body, the manual lever must be moved to the right and pushed in
to lock in place (this manual lever is used when filling, venting and draining the installation).
Position the actuator over the spindle ensuring the two locating pins on the actuator mate with the
bosses on the body and press down. The actuator will lock into place automatically (an audible click
will be heard)."

So, the removal procedure will be to turn off the boiler demand - so no CH or DHW is being called for. Then move the MA1's 'manual' lever to the right and lock it open. Press the release button, and gently wiggle and pull off its head.

With the head off, check the valve spindle for any corrosion or deposits around it - post a photo if you can. Grab it and rotate it back and forth - it will only move a short distance, but it should move freely and end with a crisp 'thunk' at each end of travel as the valve bottoms-out.

Does it? If it does, the valve is fine. If it's tight and sticky at any point, then that could be the issue - and that means a new valve.

Position the valve's spindle roughly mid-way so the valve is open both ways, and then turn the power back on. One person observe what happens with the actuator head whilst the other person goes from DHW only, to CH only, to BOTH, to... and watch the wee indicator lever (and listen to the motor). Does it go 'whirrrr' smoothly and decisively? It should only take 2-3 seconds to go full travel.

Report back.

TMSG

ThisIsWeird said:

Well, the key thing to take from all this is, YOU LISTEN TO BBC R4 IN BED! Awesome!

cough

The world looks in slightly better shape if I listen to the news still half-asleep

Thanks for the detailed write-up, I've been on the Drayton website a few times but this guide is news to me. So I will have a cuppa, study this and then we'll see. More probably tomorrow

Albermarle

) we do not have a combi or condensing boiler. HW is kept in good-quality storage tank in airing cupboard.

If the boiler is not a condensing one then it must be rather old. The condensing part is to increase the efficiency of the boiler and is not specifically related to your HW.

TMSG

@Albermarle Yeah, I know.

I just mentioned that our boiler (2011) ain't condensing because @Lorian (1st reply) mentioned condensing.

TMSG

@ThisIsWeird (It turns out the pdf you linked to was the same "manual" I had already downloaded under another name.)

OK, so I did what you outlined above. The valve itself seems perfectly ok, no rust, no dirt and it can be moved relatively easily (though as you said only a small way). When there's no water flowing there are no sounds at all but when the water flows, it makes pretty diabolical THUNK, with the pipework visibly shaking for sec or two.

I left the MA1 off the valve, the argument being that if it's not connected to the valve it has no real work to do, if you know what I mean. The thing goes reliably from HW to CH and when it's on CH on only and HW is switched on, it goes to mid pos (as it should). However, if we then switch off CH but leave HW on, it should go to HW (I think) and it does... sometimes. At other times it just remains stuck on mid pos. So... I think it's perhaps not totally broken but not reliable either. What's your (or others) take?

Also, there's something loose inside the actuator, a rattling noise if the things is moved or shaken.

EDIT: And a further Q... if I wanted to replace just the actuator itself (not the valve), is it then a question of a 22/28mm version? It seems the actuator is the same anyway but not at all sure./EDIT