Central Heating System Confusion

Thanks for your input. Didn't mean to start an argument.

As I said, my plumber didn't really have a clue so now I'm more clued up it's time for me to call in a heating engineer or whatever they're called in the trade!
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Hey, thanks for that. I found a wiring diagram elsewhere (with the wire not the relay) but I've had a look at my junction box and it's not the same as these diagrams. Mine only has 8 blocks, not 10. Sure enough there is no wire going to the programmer for HW off. Couldn't quite follow the rest of the wiring, but obviously somethings not right when there's only 8 blocks of connections not 10!
What you should have done was stuck with your first thread, and it would have been sorted by now.

And you still have the original problem to sort out as well.
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Yeah some rooms are cold, so I'm getting bigger radiators. But yes, my problem is I can't have CH on on its own (I have to have both CH and HW on) so every time I call for CH the tank also has to heat up, which obviously takes time and means it takes best part of 2 hours for all rads to get hot.
Hello... I've been searching this forum trying to get my head around my central heating system and I'm not really any the wiser. Would be grateful for any clarification - never knew there were so many systems out there.

Basically I've just moved home and can't figure out exactly what's wrong with my system. I have a Worcester 12 Ri conventional boiler, British Gas UP2 programmer, cold water tank and expansion tank in the loft, cylinder upstairs with stat, grundfos pump and sunvic valve, room stat downstairs.

I thought my system was gravity fed but from what I read on this site this is a common mistake to make and now I believe it is called Fully Pumped, and I'm guessing in a Y Plan (can anyone confirm?).

The problem I've got is with my programmer. When I select HW I get hot water but when I select CH, I get CH and HW. I removed the programmer from the wall and on the jumpers on the back it was set to independent (not linked) HW and CH, but the system was set to Gravity Fed, not Fully Pumped. I changed it to Fully Pumped, put it back on the wall and turned CH on but nothing happened.
Set it back to gravity fed, put CH on and as usual, CH AND HW came on.

On the back of the programmer is a wiring diagram:
1. HW Off
2. CH Off
3. HW On
4. CH On

On mine, ports 1 and 2 have no wiring going to them. Is this my problem, or could it be a dodgy 3 port valve?

Seen this a few times with BG systems, you can't select CH on it own. Daft I know but it's done to speed up the install. As said you could sort it out with a 240Vac/240Vac SPST relay or just wire in the HW off on the programme & NO or SAT on the cylinder stat, as it should be.
You can't do that with a Y plan unless it's wired wrong Dickie
You don't need a relay. Just connect grey to HW off.

In the time controller or the cylinder stat.


I think the problem is more than that.

The programmer is set to gravity primaries, and when you change it to fully pumped nothing works.

If the wiring is changed DIA, the DIP switch or whatever would also need to be changed to Fully Pumped.

Christ, I wish I had a pound for the number of times I've had my head buried in a cupboard with a torch & multimeter sorting out cr.p like this!! Some of it is not always a clueless botch, like the single zone valve on the fully pumped system & the programmer set to 'gravity'. All just to save a few quid. I'm sure you've seen it all before DIA.
You can't do that with a Y plan unless it's wired wrong Dickie

Oh I'm sure it's not wired like a 'Y' plan DIA. Ever seen it where they use the mid-poss valve as a divertor valve?? The grey & white is connected together!! Gawd knows what that does to the Resistors or Diode??.................. :LOL: :LOL:

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