CH not working as expected

I'm having a problem with my central heating which someone might be able to help me with.

My system has the usual boiler, pump, valve, cylinder and room stats. The programmer is a Landis Staefa RWB2E with separate controls for the CH and HW. However no matter what I do to the room stat, I cant get the central heating to kick in without the HW on and the cylinder stat set to a high temperature, eg 80 deg which apparently doesnt do the cylinder life expectancy any good.


I've gone through the wiring and drawn out all the permutations of Cylinder stat, Room stat, CH signal and HW signal, measuring the voltages at various points in the circuit.


It boils down to the boiler/pump voltage only going live when the cylinder stat is set high and the HW signal from the programmer is live.


I copied this diagram from http://www.diyfaq.org.uk/plumbing/plumbingpage2.html#valves as it seems to be exactly how my system is wired. The only difference is the grey line from the valve isnt connected to the "HW not wanted" signal which is available at the programmer but isnt wired up. Is this necessary and doesnt it mean the programmer will be short circuited when the cylinder stat is in the satisfied position?

[code:1]
PROGRAMMER VALVE
OUTPUTS: CONNECTIONS:
/
CH wanted 0----o o-------White
room stat

HW wanted 0----
| Orange<--
o |
/ tank stat |
o/ o---------------------OBoiler/pump
|
HW not wanted 0--------------Grey
[/code:1]

In the description on the above website, it states:

"If, however, hot water is not required OR the tank stat indicates that the cylinder is hot enough, the grey wire will also be energised, and this will wind the valve to the B position. The *valve* will then supply the boiler/pump via the orange wire."

Click to expand...

This doesnt happen in my case as the orange wire stays low. The valve is a Honeywell and it has 9221 on the case.

Anyone any ideas? I can give more details if needed.


thanks

Mike

[/url][/quote]

the grey line from the valve isnt connected to the "HW not wanted" signal which is available at the programmer but isnt wired up. Is this necessary?

Click to expand...

Yes it is!

Try a proper wiring diagram:
http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.4 Y Plan.pdf

Thanks for the diagram link.

I wonder why the cowboy who put the heating system in (before I owned the house), neglected to put this wire in. What a nightmare - I cant see how I'm going to get this extra connection done without ripping out lots of plasterwork and tiles

I take it the fact that the HW high and HW low being connected together doesnt cause a problem?

If you mean HW on and HW off connected, the problem will be you can never switch the HW off.

Can you pull the existing cable out from behind the tiles? If you can, you could pull another cable in with an extra wire in. Best to pull in a 5 way cable. If you can't do this, look on the honeywell site for a wireless version of controller, that way you wont need wires.

If you mean HW on and HW off connected, the problem will be you can never switch the HW off.

Click to expand...

I was thinking more about when the cylinder stat is in the "1" position the HW ON and HW OFF will be connected together - but the programmer must be able to handle this as its the recommended connection. Just seemed odd.

I was thinking about the pull through option and it would probably work but the fear of it snapping mid pull, and given the boiler has been given a death sentence by the service engineer, I may as well wait till a new boiler is put in as it will involve re-siting and rewiring.

Thanks for those who took the time to reply.