Combi boiler wiring advice please

[Gavsparky]

Hi all, I need I little guidance on this particular system I have which is. I have a combi boiler with a L/N/E/SL I also have a programmer, 2 zone valves each operating upstairs and downstairs central heating which are on 2 separate room stats. Now say if I'm wrong but I can't see past the room stats if one was to call for heat then the other zone valve operating also as there is only 1 SL terminal at the combi. Sorry if this is hard to understand but this picture might help but like I say there will be 2 x room stats to operate independently. Cheers in advance.

 

[snowhead]

Scrap that diagram it's no use to you.

Programmer enables the stats.
Each stat opens it's respective zone valve.
The open zone valve/s calls for the boiler.

 

[Gavsparky]

Cheers for the quick reply. I realise that the room stats can operate each zone valve independently but as it is supposed to also operate the SL of the combi I can only see both zone valves opening together as they will both be connected to the SL?

 

[snowhead]

Cheers for the quick reply. I realise that the room stats can operate each zone valve independently but as it is supposed to also operate the SL of the combi I can only see both zone valves opening together as they will both be connected to the SL?

Stats aren't connected to the SL.

Download, print, read and save this;

http://www.google.co.uk/url?sa=t&rc...=Qd4BSatG4DdkbJivdcpI5Q&bvm=bv.55819444,d.ZGU

 

[BoredSparky]

Standard 's' plan set up with two heating instead of heating and hot water. Both oranges connected together as switched live to boiler enables either zone to fire the boiler when it's respective room stat calls for heat. The second zone valve will not operate due to having a 'backfeed' up the orange. Hope that makes sense.

 

[Gavsparky]

Standard 's' plan set up with two heating instead of heating and hot water. Both oranges connected together as switched live to boiler enables either zone to fire the boiler when it's respective room stat calls for heat. The second zone valve will not operate due to having a 'backfeed' up the orange. Hope that makes sense.

Thanks for the help mate. My thinking was that if both oranges were connected to the SL to boiler to fire it up, then both zone valves would operate. Forgive me if I'm being dense!

 

[Gavsparky]

Stats aren't connected to the SL.

Download, print, read and save this;

http://www.google.co.uk/url?sa=t&rc...=Qd4BSatG4DdkbJivdcpI5Q&bvm=bv.55819444,d.ZGU

Cheers for the help mate. I could be in for a night of reading up with that haha

 

[yellowvanman]

You need the outputs from the controller going to the stats and when the stats call to open the respective valves.

Then using the internal relay on the valves (grey and orange), connect both greys to the unswitched supply and both oranges to the boiler call.

So if one stat is calling for heat it will open the respective valve, once that it open it will call the boiler and won't back feed the other circuit.

You probably need a wiring centre to house all the interconnects.

 

[Gavsparky]

You need the outputs from the controller going to the stats and when the stats call to open the respective valves.

Then using the internal relay on the valves (grey and orange), connect both greys to the unswitched supply and both oranges to the boiler call.

So if one stat is calling for heat it will open the respective valve, once that it open it will call the boiler and won't back feed the other circuit.

You probably need a wiring centre to house all the interconnects.

Brilliant I think I'm nearly there with that, the only question I have is where does the unswitched supply come from (grey) thanks mate

 

[yellowvanman]

Brilliant I think I'm nearly there with that, the only question I have is where does the unswitched supply come from (grey) thanks mate

Supply to your controller?

 

[BoredSparky]

Grey - permanent live, Blue - neutral, Brown - live feed from room stat/programmer, Orange - switched live to boiler

 

[Gavsparky]

So to sum it up, we have a core from the controller supplying both stats then in turn, each switch wire from the stats will be connected to the grey of the zone valves respectively, then both oranges connected together will return to the SL of the boiler? Am I right in thinking

 

[BoredSparky]

No, permanent live to grey on each valve, feed from programmer/stat to brown on each valve, both oranges together switched live to boiler

 

[Gavsparky]

No, permanent live to grey on each valve, feed from programmer/stat to brown on each valve, both oranges together switched live to boiler

Cracked it! Thanks for your help got there in the end

 

[yellowvanman]

So to sum it up, we have a core from the controller supplying both stats then in turn, each switch wire from the stats will be connected to the grey of the zone valves respectively, then both oranges connected together will return to the SL of the boiler? Am I right in thinking

No.
Assuming both zones are controlled by one timer, call from the programmer goes to the stats.
Stat call goes to the respective valve (brown) to open the valve.
valve greys are connected to the supply for the heating (programmer supply - unswitched)
valve oranges are connected to the SL of the boiler.

I suppose the grey and brown of each valve could be connected together if you can't connect the greys to the heating unswitched supply.