CH Not Working - Suspect Mid-Position Valve

[MANDATE]

Yes When CH and HW are not ON there is still a 'live' wire from the HW OFF terminal to the 'grey' wire of the actuator, so make sure all power is removed before any work carried out

 

[fouxdafafa]

A quick update. I bought a replacement motor for £13.49 (approx!), fitted it, and now the valve seems to be working OK. At least, when I select the various combinations of H,W, or both, I see the the indicator moving on the side of the actuator, and the boiler fires. I have a query though. When I felt the pipework coming from the valve, even though I had H only selected, the pipe going to the cylinder was fairly hot, so I'm supicious that water is going that direction as well. Thinking about it, I'm wondering whether I should expect that pipe, which is quite short, to be the same temperature as the stored water in the cylinder - which could have been quite hot at the time I tested it. I suppose the only way to know for sure is to let the cylinder go cold and then try the heating on its own. Does that make sense?

 

[seco services]

Makes sense but more likely the paddle is passing on the HW side worn/port got crud around it stopping it fully closing.

 

[fouxdafafa]

Ta. I have no idea what a mid-position valve looks like inside, but I get the gist of your comment. And is there a solution? New valve?

 

[seco services]

useally yes.

 

[coldbutclean]

Hi first post so please accept my apologies if I have tread ones toes - I have read and read and read trying to make sense of my central heating fault I have also spent days googling the issue to no avail so any help would be apprecaited before I resort to draining the Central heating and removing the mid position valve to find thats not the issue.

System - vented Y plan - installed 1989, microbore to rads 14of.

Fault: No central heating but hot water
Check voltages across all relevant contacts and found as should be thanks for the info in this place.

Checked mid position vale spindle moves as the one I have bought to replacement £75 ouch.

Replacing mid position valve actuator/ head with new drayton MA1
same fault.

Removed PCB from old actuator head - and manual press microswitch - pump fires up and tries to pump water, but pipe to rads - does not heat up no signs of water moving through system.

does this sound like the valve inards have (sorry for the wrong term) collapsed and despite the spindle moving the inards are not or it is in fact an air lock in the pipe.

I have bled all the rads.

Thanks for any help you can give

 

[Agile]

Something is still preventing a flow on CH.

I would turn all the rads off and examine just one using the bucket test to check flow to each side.

I presume you have checked TRV pins and all the basics as described in the FAQ first ???

Tony

 

[coldbutclean]

Locked off all rads bar the one with drain off valve downstairs

After releasing several pints - hot water was coming out of the drain valve , is this back draining from somewhere else in the system as the pipe feeding the C/H from the side of the mid position valve is still stone cold - ( well about 8 -10 inches along pipe from the valve body are hot.) should this not have heat up as hot water ran through the system to the rad I drained ?

The system has a manifold could this be blocked and restricting flow ?

I have no idea where it is but have been told as the system is in microbore it will have one.


any thoughts cheers rob

 

[coldbutclean]

After draining several pints of water from various rads - at each flow return ( locking off each side in turn - a few of the rads came on - then went off never to come on at the same time again.

I managed to get the bathroom rad (towel rail), closest to the airing cupboard very hot - but the pipe next to the mid position
C/H feed ? is still cold after the first 10 inches - does this sound like this pipe is furred up - the water is jet black in the system -

I have now put in 1.5 bottles of X400 - as 12 rads

I did manage to get individual rads hot by locking one side off and draining - some have drain off valves

can i partially drain the system - set the mid position into HW only (I does it do this at rest automatically - lock off the pump - - turn off the 15mm pipe return to the boiler at the bottom of the tank - lock off the valve on the C/H feed - then take out this section of pipe just after the mid position ?

or will I end up in hot water