Are you saying that the timer also controls the pump, so you have: a) Nothing at all; b) Everything at once, valve, pump & boiler?
And how does the Hot Water side of it work?
Just curious. Well done getting to where you are now.
Yes, the timer is /supposed/ to control everything. It has outputs for CH on and HW on. These are supposed to activate the motorised valves, which act as relays for the pump and boiler.
The timer output for HW goes to the cylinder stat, which then goes to the HW motorised valve.
The timer output for CH just goes to the CH motorised valve.
They actually do a bit more than that! They enable the CH and HW to be controlled independently of each other, so that you can neither, either, or both on at any point of time. If you *just* had a relay without the valve, *both* the CH and HW would be on whenever the boiler and pump run.
Good. That's what it is supposed to do.
Bad! But it's trivial to insert a room stat between timer and valve - particularly if you use a wireless stat so that you don't have to disturb the decorations by inserting new wiring.
Yes, I was over simplifying.
Yes, that bit of the wiring makes sense.
I'll definitely do that. Wiring it wouldn't be too bad, since the living room is directly below the main terminal block, but wireless anything is always nicer.
snip
It also ensures that the boiler does not light until at least one valve is open. A few seconds might not matter for an old, relatively massive boiler, but it could be harmful if the valve actually failed to open at all.
I was thinking more of not having the valve at all, since it's wired direct to the timer (and at first I thought it must always be open), but then I realised that you can't then have the HW timed on by itself. As usual, these things make more sense when I've had a chance to think about them :-)
Not if you want reliability. And to not come home to a boiling house every time the batteries go down.
NT
I would suggest that you study some of the standard Plans, C, S, etc, and see which of them most suits your setup, with an added Room 'Stat. Then use the best one as a guide to how you rewire yours. The design work has been done already, what you have to do is select the best implementation of this work.
Oh, right. I'd imagined one plugged into a spare mains outlet.
Good idea. The manual has one that's pretty close, I think.
I replaced the batteries when I moved into this house in late 2010, and they are still working fine.
Doesn't sound too bad, then. I always think wireless things are going to use a lot of power. And at least if it does run out, it will just be exactly what they have now. I've seen some that have a battery power warning light. Maybe they all do. Do they just have a receiver that you wire in where the normal stat would go?
Mine isn't wireless, though. Sorry if there was confusion. It's wired functionally to the controls, but gets its power from the battery. It always seemed an odd way to do it, but then I believe it's made by Siemens, who do know a thing or two about electrical stuff. But as for wireless things and power, my oil tank level monitor is wireless, and it's been there for a couple of years or more now, and still works. The receiver is plugged into the mains. I believe that the transmitter uses a button battery.
They just need a receiver at a convenient location - often near the boiler so that very little wiring is required. The receiver units are mains powered, with just the remote stat and display unit being battery powered.
Being wireless, you can easily experiment with the best position for the remote stat - or even move it from room to room depending on your priority at any given time.
[OK, the room where the stat is shouldn't have a TRV on its radiator so, in theory, if you move the stat to a different room you should then remove the thermostatic head from that room's TRV. I don't always bother!]
It was the CH zone valve microswitch. Thanks to all who responded. In case anyone's interested, the normally-closed microswitch had broken its rather flimsy pegs, and was dangling free. For now, it's JB-Welded into position, and seems to be working. I'll add a room stat to it soon - mum and dad like the heating on even in summer, so a room stat might save a bit of money :-)
Glad it got identified.
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