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Drayton MA1 mid Postion Valve not Resetting to Hot Water

Postby Oldschool BMX » Wed Sep 06, 2017 2:27 pm

Hi Folks,
First timer here so go easy on me!!
I have tried looking at past threads but have been unable to find an answer to my dilemma, so I apologise if this question has been asked in past.
Just recently had to change my ACL Lifestyle mid position valve as a result of the rads getting hot when HW only was called for, which was due to old age, crap in the system and port A not fully shutting off. The new valve I fitted is a Drayton MA1, like for like swap on size and wire colours.
Both CH & HW work fine now, however, when I create a demand – via room thermostat - for CH only the motor energises and moves to the CH position, when I turn off the room stat the motor does not return to the HW position and gets very hot after some time, it only returns if I create a demand for HW or if I remove all power to the system by turning off the fused switch.
It would appear that the valve is picking up some voltage form somewhere preventing it from resetting because of the internal switches not set correctly or the valve is knackered although I may be wrong.
Is this something anyone has experienced or come across? If so, what’s the solution as I don’t want to fork out unnecessarily if it’s something simple to fix.
All help and advice would be greatly received. Thanks in advance.
Oldschool BMX
Oldschool BMX
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Simply Build It

Postby ericmark » Fri Sep 15, 2017 7:44 am

I had problems with my daughters old house, typical new baby so critical and a Sunday so had to find it parts required before shops closed at 4 pm. As an electrician I thought it would be easy, I found a wiring diagram for Y plan and tried to follow it.

However the plan shows one micro switch in the valve, in fact there are three, so meter readings were not as expected at the junction box. I was not sure it was the three port three position valve at fault, but as 4 pm approached I bought one anyway.

It worked and after it was all up and running we were able to work out what had happened. It would seem the fault was there before my daughter had bought the house, some one had latched the valve to mid position which resulted in radiators getting slightly warm in the summer, however daughter had not noticed this.

My son-in-law had tidied up the airing cupboard and had caught the leaver unlatching it. Result was when domestic hot water was required it motored open, but it did not open when central heating was required, however if the central heating was required then once the hot water was run, it would stay working until the thermostat turned it off again.

I would guess one of your micro switches inside the motorised valve head is sticking causing your fault, however although you can get V3 micro switches, in real terms it would mean new head.
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