Help with central Heating!

[boffa]

Hi Guys I am a newbie on this site but I need your help. I have a heating system with a cold tank in the loft, a boiler in the garage and a cylinder in an airing cupboard. All was ok but in the summer I noticed my rads were on whilst the heating controller was switched to off and the room stat was wound round to low. A friend assured me it was my 3 port valve sticking so I found this and swiftly took the head off and set about working the valve back and forth with pliers, and this done the trick.(The Valve is an ACL 22mm mid pos valve) Anyway weather that's related to my current problem I don't know. All was working fine until yesterday when I noticed the Rads were off yet the room stat was turned up. So I turned the stat to 30 and realised that the pump was not kicking in. On turning the cylinder stat up, the pump kicked in straight away which, I'm guessing rules out the pump. Now this is what's confusing me. If I turn the hot water off at the controller, and the room stat up, the three port valve will move to the rads position and the pump kicks in ok. If I wind down the room stat the pump kicks out and everything is fine. The problem is when the hot water is switched on at the controller. All the time the hot water is calling for heat, the system works ok, until the cylinder reaches it's temperature when the pump kicks out and shuts the rads off. If I wind the roomstat up to 30 it has no effect on the pump. I have to turn the hot water to off at the controller to get the 3 port valve to swing to rads and the pump to kick in. Is this usual when a mid pos valve goes wonkey or is this a controller fault as I am confused as which one (If any) is at fault. Your help will be appreciated.
Steve

 

[sonray ltd]

if your valve is not moving when hw satisfied by cyl stat and the only way to get it to move is turn off the hw at programmer sounds like your cyl stat is not giving a satisfied signal which will be on the grey wire.

if you can get the cyl stat up to temp so it shuts off check for power on the grey wire in the wiring centre.
the grey recieves power from two places cyl stat satisfied or hw off at programmer.
it needs power on the grey to shut the hw water port off.

 

[boffa]

Thanks Sonray
If I turn down the cyl stat whilst the cyl is calling for heat when the dial reaches the tank temp the pump stops running. If everything is working fine the valve should swing to rads and kick the pump back in at this point, yes? It dosn't unless I turn the hot water off at the controller. So you thing it might be a cyl stat problem?

 

[sonray ltd]

yes find you wiring centre and check for power on the grey.

or the stat satisfied wire may of come loose etc.
should be 3 wires in the grey terminal.

 

[boffa]

Ok I took the grey wire from the cyl stat out of the choc bloc whilst the cyl was calling for heat and the pump stopped running. when I reconnected it the pump started running but do I need to check there is power on it when the cyl stat is not calling?

 

[sonray ltd]

that don't make any sense unless you have a grey on the stat.

what colour are the wires in the lead to the stat ?
their should only be 1 grey and thats from the valve.

 

[boffa]

Sorry
What I thought was a grey is a very faded brown. The other 2 from the cyl stat are blue and yellow/green.

 

[sonray ltd]

right i would say the brown is common power to stat.

one should join in a terminal with orange. live when calling for heat
one should join in a terminal with grey. live when satisfied.

don't remove any just check for live when stat satisfied on the x terminal (one will be grey)

 

[boffa]

Ok
The yellow/green from the cyl stat has red sheathing on it and goes to a choc bloc with a grey which goes to the mid pos valve. I am not 100% up ou what I am doing with the meter I have but with it set on v and with the pump running I have a reading of 3 on that terminal. When I turn the cyl stat down (so it is satisfied?) the reading on that terminal goes to 7

 

[sonray ltd]

3 or 7 ? you need 230v etc
v useally v with a wavey line next to it. and does it have any numbers like 200, 400, 600 etc.

 

[boffa]

Just to let you know guys......I changed the mid pos valve about a week before christmas and immeadiatly it solved the problem..... until yesterday when the problem came back! So taking Sonray's advice I changed the Tank Stat and again the problem has gone, so here's hoping this time!

 

[sonray ltd]

that long ago i forgot the problem.