Replacing an old CH/HW programmer

[Tankrizzo]

Chaps,

We've been in our house for a couple of years now and it's probably time I looked at replacing my aging CH controller. The system is a fully-pumped affair, with a conventional boiler downstairs, cylinder upstairs (no immersion), wall-mounted stat in the hallway and this thing upstairs on the landing.

It's an old ACL Lifestyle LS112, I don't even know who makes this but having a bit of a Google, it looks like it might be Drayton now. The main problem with this old controller is that it doesn't allow me to separately control CH and HW - I can either have HW on, or HW + CH. As the CH is stat controlled downstairs, it would be nice to be able to have the hot water circuit on a timer and the CH on constant, regulated by the stat. As it stands at the moment, if I have the heating on and regulated by the stat, the HW is also on. This is obviously not very efficient.

The system is governed by a mid-position valve, here:

So, two questions really. Firstly, what is a suitable replacement for this controller? I don't need anything too fancy, just something with a timer which will let me independently control both circuits.

Secondly, how easy are these things to wire in yourself? I'm a reasonably competent DIYer and if it's a case of "put wire X in terminal B" then I have no problem with that. This is how the wiring in the controller junction box currently stands (I probably will replace the junction box as well as it's horrible):

 

[D_Hailsham]

That's not the correct programmer to have with a mid-position valve! The system was probably converted from pumped heating/gravity HW to fully pumped but they didn't want to spend the extra money on the correct programmer.

Rewiring to a new junction box is probably a good idea. But make sure you know where each wire goes (label them) before disconnecting anything.

If your programmer is that old, the thermostat is probably just as old. So it might be sensible to think of a programmable thermostat. The Honeywell Sundial RF² Pack 2 would be a good choice.

 

[jackthom]

Hi you might find this explanation with diagrams of the Y-Plan useful before getting stuck in.

http://octaveblue.co.uk/c_heating/


(The diagrams assume that the pump is controlled directly by the boiler. In an older system where that isn't the case the pump's live wire would be connected to terminal 8.)

 

[Tankrizzo]

Thanks guys. That's what I suspected then. My roomstat in the hallway is actually not that old as the last one broke and I simply replaced it with the equivalent new, basic dial-type Wickes one as a temporary measure. I'll replace this with a digital one when I do the programmer.

The main problem I have is identifying which bloody wire is which in the junction box! None of them are marked, and although on the inside of the box lid there is this diagram (see below), the wiring doesn't seem to bear much relation to how that says things should be (the roomstat for example according to that diagram isn't even wired in).

I suppose I need to separate the circuits out into two channels as they're currently wired in for 1.5 channel operation. This is where the main difficult will lie as I don't know what is what.