Central Heating System Confusion

[Alfie25]

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:
Neutral
Live
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?

 

[matt1e]

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

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

If you mean terminals 1 and 2 have no wiring going to them and you are yplan then you will need a connection to HW off (1)
if you are splan then only hw on and ch on are req
how many ports does your valve have, 2 or 3?

Matt

 

[bell824]

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?

if it is indeed a three port y-plan valve then that is most certainly your problem, there is a wire on the 3 port valve for hot water off, it needs to be told both from the clock and the cylinder stat!!!

 

[Alfie25]

Terminals 1 and 2 in the programmer have no wiring going to them. I believe I am Y plan as there is only one motorised valve (AFAIK) - which I believe is a 3 port valve - the Sunvac Unishare.

This valve has one pipe going into it, then one pipe pointing to hot water and another pointing to central heating. So it would seem as you both say that there should be a wire going from the 3 port valve to the programmer. Will this mean fitting a new wire from the valve to the programmer (routing through the florboards and chasing down into the kitchen wall where the boiler is) or will there already be one behind the programmer, just not connected?

 

[bell824]

more than likely never wired correctly and therefor no wire in place and a new one required!

you may find the Sattisfied from your cylinder is already to the zone valve but the proggramer needs the h/w off (same as satisfied) wired to it to move the valve to the central heating only position.

 

[Alfie25]

Cheers - sounds like it was never wired correctly. On the back of the programmer as I mentioned, it is set to gravity fed not fully pumped as it should be. A British Gas bodge. Looks like I'll have to get a sparky to wire in a conection from the MV to the programmer.

As for the other wiring... is there a way I could check if there is wiring from the cylinder to the MV to say that it is satisfied? As it stands, if I have the HW on only and the cylinder reaches the stat temp, then the boiler will shut off, but I'm guessing this isn't the same as having a conection between the cylinder and the MV to say it is satisfied?

Suppose I could put the HW only on till its up to stat temp, then turn on CH and see if it diverts to CH only, but the problem is I think it would permanently divert to both CH and HW as it tries to keep the cylinder up to temp.

 

[matt1e]

So it would seem as you both say that there should be a wire going from the 3 port valve to the programmer. Will this mean fitting a new wire from the valve to the programmer (routing through the florboards and chasing down into the kitchen wall where the boiler is) or will there already be one behind the programmer, just not connected?

if you're lucky but I doubt it!
Yes we are saying that, don't worry though you can still make it work with out having to chase walls etc
you will need to wire in a relay though

 

[Alfie25]

Been a long time since i did GCSE electronics! So are you saying a relay would do the job instead of having a wire installed directly from the MV to the programmer?

 

[matt1e]

yes Mate

 

[bell824]

yes mate !!! i doubt it a relay wouldn't cure it.

Only properly wiredwould cure it !!!

search for Y-plan wiring and that will cure it, basic electronics it aint but if you get a good linear diagram(i have one but it is a drawing of mine ) it is pretty well self explanitory the valve needs to know when hot water isn't required, either via the cylinder stat or the proggrammer

 

[matt1e]

yes mate !!! i doubt it a relay wouldn't cure it.

Only properly wiredwould cure it !!!

oh ye of little faith!

the valve needs to know when hot water isn't required, either via the cylinder stat or the proggrammer

or a relay feeding 240v to the grey when hot water is not in demand perhaps

too drunk to do a diagram now but will do tomorrow
I'm sure I've explained it on here before though

Matt

 

[bell824]

look forward to seing how a relay would cure an difinite off comand

 

[matt1e]

look forward to seing how a relay would cure an difinite off comand

you posted before I had finished editing my post so refer back to my earlier post to give yourself a clue

(Not that the above makes easy reading if you say it quickly mind you )

 

[bell824]

still dont see how a relay can replace the hot water off comand though!

 

[swbjackson]

I think I can. You could use a relay to liven up the grey wire on the 3 port when there is no power to the common on the cylinder stat.