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Hi,
I have just had a problem last night with my h/w & central heating system,
I have found out the boiler has been stopping and starting without the c/h 2 port valve opening,
I have tested the circuit and discovered it is the micro switch in the valve that must have stuck in the closed position when I turned the stat off last night.
My question is - instead of the grey wire being a permanent supply to the micro switch, can I move it to the terminal with the brown wire which only becomes live with the stat,
That way if the micro switch sticks it will still be controlled else where and won't send a call to the boiler all night?
 
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Paignton pete

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No don’t do that, but you can move the little handle on the side of the two port valve that should lock into place to leave it permanently open.

Is it the hot water or central heating 2 port valve?

This is a temporary fix only.
 
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  • #3
Its the C/H 2 port micro switch that stuck last night,
is there a reason the micro switch cant be a switched live
 

Paignton pete

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now you’ve got me thinking. My previous post may not be too helpful.

I’m not sure why 2 port valves need a permanent live at all.

in a normally closed 2 port valve surely a switched live feed via a thermostat would be enough To make it open and sent a call to boiler and pump.

Hopefully someone else can pop along and tell us why.
 

Midwest

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I think the micro switches are used to preventing one valve making the other valve permanently open. Guess as the other valve micro switch is still working, you could do as you suggest, as a temporary fix.
 

suffolkspark

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Yes that will be fine to do, just means the load of the boiler will be going through the programmers relay rather than the micro switch but should be ok anyway, shouldn't get any back feeds or other valves opening
 
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  • #7
YES your 100% right Midwest, Thank you.
I can see now that the H/W calling would also send a feed to the C/H valve and open it as well,
I can switch off the H/W and use the element for now until i get a new valve,
Thanks again.
 

davesparks

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Yes that will be fine to do, just means the load of the boiler will be going through the programmers relay rather than the micro switch but should be ok anyway, shouldn't get any back feeds or other valves opening
No it isn't because it will get a backfeed from the other valve(s) if they are on when the s/l goes off. Thats the whole reason the grey wire was added to valves.


Post automatically merged:

Its the C/H 2 port micro switch that stuck last night,
is there a reason the micro switch cant be a switched live
It can't be the switched live from the thermostat because it would suffer a backfeed from other valves. Some early 2 port valves suffered this problem because the microswitch was internally connected to the motor L, which was fine if here was only one valve but a relay was needed to use them in a S plan style system.

It can be connected to the switched live from the programmer of absolutely necessary as the thermostat would then interrupt any backfeed to prevent overheating, but you will still get some backfeed until the thermostat switches off.
 
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Lucien Nunes

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Edit: realised that as it is CH valve it must be physically closed or you would have noticed by the rad temp.

As SJT & DS note, feeding the microswitch grey PL feed from the same controlled supply as the motor can cause backfeeding and incorrect operation if the orange output wire is commoned between multiple valves. One valve on its own will open and close and control the boiler correctly, but as soon as multple valves are open at once, a circuit is established via the microswitches that links their motors together. They will all remain open and the boiler fired while any of the controls is still calling for heat. When that goes off, all valves will close at once.
 

PEG

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Pretty much covered,here,but it is worth noting,that the mechanical lever,to open the valve manually,does not always open it completely. Some are just for drain/bleed purposes.

On occasion,this restriction,can cause the boiler to trip on the over-heat stat.
 
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  • #11
I have cleaned the micro switch and it seems to be working ok now but i think i will run the permanent live that feeds the micro switch through a n/o contactor and control the coil from the room stat feed,
that way if the micro switch fails again the boiler will still switch off.
 

Midwest

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Why don’t you just replace the faulty valve head, and fix the problem?

Edit; you can even just replace the micro switch. In my experience, it’s more economical in the long term, to replace the whole valve. Saves revisiting things.
 
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Midwest

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YES your 100% right Midwest, Thank you.
I can see now that the H/W calling would also send a feed to the C/H valve and open it as well,
I can switch off the H/W and use the element for now until i get a new valve,
Thanks again.
Did it work ok?
 
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