Drayton 22mm mid-postion valve woes

[Ptibbitts]

I'm on my 4th Drayton mid position MA1 valve in two years and wonder if my problems have been discussed before, with any results or suggestions greatly appreciated.....

The pottery on programmer will allow the valve to operate in the normal way, i.e. hot water only, heating only, or mid -position with both services activated.

(I'll add at this point to say I have changed the brass valve body each time the Drayton has failed, although it was finding - turning free each time.)

The issue I have is that the failures occur after the Heating regularly comes on at say, 05.00 hrs each morning until 09.00 hrs.

During this time the Hot water comes on at 06.00hrs and is set to go off at say 07.30hrs., however, as the Hot water switches off at 07.30hrs as planned it switches the complete system off ( I e. The supply to the boiler and the Heating fails to run on until it's switch-off time of 09.00 hrs

Each time it occurs I find by giving the 3port actuator head a jolt with the palm of my hand, there is a "click" ( as if a micro switch is released) from being stuck and is activated into switching the pumps back on and presumably the boiler supply re-activated and the system then fires back into service until the correct switch off time of 09.00 hrs.

This has happed with unbelievable consistency to all 4 no. New replacement valves and actuators! ( And I'm more than fed-up with replacing the valves and actuators.

Couple of my considerations:

A) the hot water cylinder thermostat is broken? - but this seems to work ok and is not instrumental in switching the hot water service off - the hot water is switched off by the programmer, so I've discounted replacing that.

B) The micro switches in the actuator are stiff? - but the actuators are all brand new , so shouldn't be a problem.?
Valve set-up
C) The Hot water never reaches the thermostat set temperature, so the stat. is still actually calling for heat, when the programmer switches the Hot water off side of the program off.
At which point the system should switch to Heating, ( that always fails!).

Should I just swap to Honeywell or a cheap Chinese eBay £25 set up?

Any suggestions gratefully received.

Cheers, Art.

 

[ericmark]

The three port valve is odd how it works, white is energised to get central heating, and it powers the motor half way, when the SW2 sends a signal down the orange to fire boiler. The grey is powered when you don't want hot water, John Ward has done a youtube video

The wiring

is here and as John says if the DHW is turned off when the central heating is running, then the valve can stick hard over, however if the programmer is left with DHW all the time, and the tank thermostat turns it on/off, next time the tank thermostat turns it on, the valve will return to rest.

Since a tank of hot water will stay hot for a couple of days, the only real reason to turn DHW off is when some other form of heating is being used, or one is on holiday. I don't use a Y Plan I use a C Plan, and I can't turn the DHW off, if the CH is running so is DHW, since not much sun in the winter this suits me, when the summer arrives then DHW is heated with spare solar power, once the house and battery are satisfied it will heat the DHW with solar before it exports power.

I would try heating DHW at the end of the CH time rather than the start, and have it so it is still being heated after the CH has turned off.

 

[Ptibbitts]

Thanks for the reply. I now know how it's supposed to work, but would love to talk to John Ward to discuss why the system is stalling, and a clout with my hand suddenly gets the supply back to the Heating service, after the hot water is switched off by the Potterton Programmer??

 

[Ptibbitts]

What would cause the microswitches to be stuck ?

 

[Ptibbitts]

A broken programmer? ( Presumably not that)? as once the 3way activator is clouted it all fires back up!?????

 

[Ptibbitts]

Which wire is responsible for driving the switches to the heating position? (The grey?) Does that get it's supply via the room stat?

Do you think the room stat is not sending enough current to move the motor towards the Heating position?

 

[Ptibbitts]

Should I check the supply from the room stat?
What sort of issue would a broken room stat display?
How to check???

 

[Ptibbitts]

Every one of the actuators has behaved in the same way - give the actuator head a clout and the system works again.

Funnily enough, the system always comes back on in the morning!

 

[ianmcd]

Check your HW off wire is wired in correctly, it should be wired to HW off at the programmer and satisfied at the cyl stat, these two wires connect to the grey on the mid position valve

 

[Ptibbitts]

Check your HW off wire is wired in correctly, it should be wired to HW off at the programmer and satisfied at the cyl stat, these two wires connect to the grey on the mid position valve

Thanks for the reply and suggestion. Unfortunately, I'm an engineer who insists on knowing how everything works and needs to have systems working correctly! (It's an engineer thing!) - there's no reason why the valve should "stick" - it's all new, and replaced each time. So I need to establish why, and correct it!

 

[Ptibbitts]

Thanks for the reply and suggestion. Unfortunately, I'm an engineer who insists on knowing how everything works and needs to have systems working correctly! (It's an engineer thing!) - there's no reason why the valve should "stick" - it's all new, and replaced each time. So I need to establish why, and correct it!

However, I will alter the hot water cycle to coincide with the heating-off cycle as suggested as a temporary repair method, untill this issue can be resolved, maybe.

 

[Ptibbitts]

However, I will alter the hot water cycle to coincide with the heating-off cycle as suggested as a temporary repair method, untill this issue can be resolved, maybe.

Maybe the Drayton motor supply is not quite up to the job, and a Honeywell valve be used.

I swapped to Drayton because of the easily replaced actuator head, but see Honeywell now have caught up and market a similar replaceable head only, unit?

 

[Ptibbitts]

Maybe the Drayton motor supply is not quite up to the job, and a Honeywell valve be used.

I swapped to Drayton because of the easily replaced actuator head, but see Honeywell now have caught up and market a similar replaceable head only, unit?

I'll also check the seemingly offending grey wire for integrity, too, thanks.

 

[ericmark]

John Ward is on this forum as @flameport micro switches do stick, and also not all valves work exactly as shown. If the grey wire is not connected it will not motor all the way across, and I have seen many where either at the programmer or the tank thermostat the grey wire is missing.

I was called to my daughters house in Liverpool when her central heating stopped working around 15 years ago and I was pulling out my hair trying to work out why. It turned out as a temp fix last house owners had latched the bleeding lever and my son-in-law cleaning up had knocked it off the latched position. It seemed the micro switch a V3 had stuck, fitted a new valve as no where was open except for Screwfix so it was what they had in stock.

The main advantage with the three port valve is default is DHW which can circulate a little with thermo syphon, so when the boiler has no cool down cycle common with older gas and oil boilers, the boiler can cool be heating the DHW. Same applies with C Plan and W plan.

As John says that diode can magnetise, and also means you need a type A RCD. But I have not worked with enough Y Plans to say if the being stuck wide open will cause problems in the long run.

 

[Johntheo5]

"The issue I have is that the failures occur after the Heating regularly comes on at say, 05.00 hrs each morning until 09.00 hrs.
During this time the Hot water comes on at 06.00hrs and is set to go off at say 07.30hrs., however, as the Hot water switches off at 07.30hrs as planned it switches the complete system off ( I e. The supply to the boiler and the Heating fails to run on until it's switch-off time of 09.00 hrs"
"the hot water cylinder thermostat is broken? - but this seems to work ok and is not instrumental in switching the hot water service off - the hot water is switched off by the programmer, so I've discounted replacing that."

How do you know that the cylinder stat hasnt switched off?, its heating the cylinder for 1.5hrs, the stat SAT, contact 2, should then provide 230V to the grey wire. Whether or which anyway, the programmer HW OFF contact should then (also) provide 230V to the grey wire and force the MPV to the CH position.

I know you say banging the valve makes it "work" but you might just consider programming the HW to be on from 0600 to 0900, the water will then be at its setpoint (60C?) and the cylinder stat, contact 2 (SAT contact) should then provide 230V to the grey wire. At least this would rule out the HW OFF contact as being the problem.
You might find the schematic, below. a bit easier to understand this very ingenious valve.