Boiler Not Firing Up For Central Heating

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Hi All,

I have problem with my heating system. I have Vaillant ecoTEC plus 415 boiler which is connected to Drayton LP822 programmer.

The problem is; boiler is not firing for central heating only. If I want cental heating to turn on, I need to turn the hot water on as well. Hot water only is Ok. Hot water and central heating together is ok as well but central heating only is not working. Our room thermostat and motorized valve has been replaced recently, so I guess they should be fine. When I change the program via Drayton programmer, I see that motorized valve is moving to all three positions without any problem. When I turn on the central heating when hot water is turned off, motorized valve moves to correct position but boiler does not fire up. I played with room thermostat, it clicks but no reaction from the boiler again.

To sum up, hot water is working like a prerequisite for the central heating. Central heating is not working without hot water.

Can you please advise what the problem may be?
 
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Thank you very much for the replies. How can I check if it is wiring or microswitch inside the valve? How can I check them?
 
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By using a multimeter at the wiring centre.
I assumed the system did work as it should at some point , did it ?
 
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By using a multimeter at the wiring centre.
I assumed the system did work as it should at some point , did it ?
Yes, ıt was working fine. Actually it started failing after the motorized valve replacement. Valve was not working properly. I got it replaced. I noticed the problem after a couple days after the replacement but I am not sure if it was like this right after the replacement. Maybe new valve was wired incorrectly.
 
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Possibly not wired correctly ,as cross thread mentioned earlier.
Show us some pics of the wiring centre, or get the installer back.
 
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Thank you very much for the replies. I have no idea how to and what to check for wiring (like which wire should be going to where etc.) . I will search it. I assume there might be some topics related to that.
 
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When I turn on the central heating when hot water is turned off, motorized valve moves to correct position but boiler does not fire up. I played with room thermostat, it clicks but no reaction from the boiler again.

If it moves to the correct position then the installer has wired that part of it correctly. Again a photo of the junction box internals would be helpful, especially one which shows the connection to the valve's orange wire. Forgive the questioning of your diagnosis, but what evidence do you have that the motorised valve (two port or three port?) moves to the correct position? When it moves do you hear click(s) from inside it? One, two, or more clicks?
 
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Front.JPG
If it moves to the correct position then the installer has wired that part of it correctly. Again a photo of the junction box internals would be helpful, especially one which shows the connection to the valve's orange wire. Forgive the questioning of your diagnosis, but what evidence do you have that the motorised valve (two port or three port?) moves to the correct position? When it moves do you hear click(s) from inside it? One, two, or more clicks?

No problem at all, thank you for your support. I changed the program from HW only to HW & CH and finally to CH only and checked if the black small pin under the valve is moving accordingly. It moves to the correct position.

I took the photo of wire box. Please see the photo attached.
 
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Then I assume it's a Drayton three port valve?
Sometimes the end-switch can fail; the valve goes to its correct position, but as soon as the hot water gets hot the CH turns off.
You may have to replace the three-port valve's head/actuator.
 
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Then I assume it's a Drayton three port valve?
Sometimes the end-switch can fail; the valve goes to its correct position, but as soon as the hot water gets hot the CH turns off.
You may have to replace the three-port valve's head/actuator.

Ok, thank you. Does the wiring seem correct?
 
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It's almost impossible to say, given that you have not specified where each cable or flex goes. If you have shown that the valve drives to the correct position (though you have not answered my specific question on the clicks) then it is quite possible that the system failure is due to a failed component of that system, ie the valve head.

PS see thread numbers 2 and 4.
How many clicks do you hear?
 
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It's almost impossible to say, given that you have not specified where each cable or flex goes. If you have shown that the valve drives to the correct position (though you have not answered my specific question on the clicks) then it is quite possible that the system failure is due to a failed component of that system, ie the valve head.

PS see thread numbers 2 and 4.
How many clicks do you hear?
I have switched between various programmes. Most of the time I hear one click but I heard 3 clicks when it was moving from HW to CH

Is the valve head that white equipment in the photo below?

sketch-1637525683652.png
.

The valve is 3 way Drayton, you are correct.
 

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