s plan with combi boiler

[sinewove]

Wired an s plan recently and used the orange from each honeywell to send a switched live back to the boiler,after removing the link.Is this the best practise way,or should the greys and oranges of the valves be bridged across the control terminals of the boiler,as voltage free contacts?Thanks for any advice.
S

 

[davesparks]

The whole external control circuit should be between those terminals!

 

[Meggerman]

Wired an s plan recently and used the orange from each honeywell to send a switched live back to the boiler,after removing the link.Is this the best practise way,or should the greys and oranges of the valves be bridged across the control terminals of the boiler,as voltage free contacts?Thanks for any advice.
S

You should feed your external controls from LN & LS and return on LR. The boiler internal fuse needs to protect the control circuit. This is not the case in a lot of what I see however.

 

[sinewove]

The whole external control circuit should be between those terminals!

Dave,
Do,nt understand that,as the signal to fire the boiler comes from the s plan valves opening,not from the room stat and boiler stat.
Regards,S.

 

[davesparks]

Which make of boiler has those terminals?
I am used to wiring Worcester Bosch boilers which have Ls and Ns for the supply to external controls and Lr for switched live, but other makes use other terminals.
A lot of combi's have just two terminals for external controls factory fitted with a link, some call them 1&2 others call them L & SL.

 

[davesparks]

Dave,
Do,nt understand that,as the signal to fire the boiler comes from the s plan valves opening,not from the room stat and boiler stat.
Regards,S.

One of those terminals is the live out and the other the switched live back.
The live out is equivalent to the permanent live feed in a basic boiler cct.

So the live coming from the boiler will feed the programmer and the greys of the valves, the oranges of the valves will connect back to the other terminal.

 

[Meggerman]

Which make of boiler has those terminals?
I am used to wiring Worcester Bosch boilers which have Ls and Ns for the supply to external controls and Lr for switched live, but other makes use other terminals.
A lot of combi's have just two terminals for external controls factory fitted with a link, some call them 1&2 others call them L & SL.

Sorry Dave you are correct, Ls, Ns & Lr.

 

[davesparks]

Ok, you were talking about Worcester too then.

My point is still that we don't know what make of boiler it is so don't know what terminals it has or what they are called.

 

[sinewove]

Which make of boiler has those terminals?
I am used to wiring Worcester Bosch boilers which have Ls and Ns for the supply to external controls and Lr for switched live, but other makes use other terminals.
A lot of combi's have just two terminals for external controls factory fitted with a link, some call them 1&2 others call them L & SL.

Dave,Its a Baxi duotech,control terminals marked BK1 L in and BK2 L out.I can see your point about using internal boiler fuses for the external controls and may alter the wiring .
Regards,S

 

[davesparks]

Read the boiler installation instructions to establish exactly how it should be connected. Which you should have done anyway before starting the job.

If they are like Worcester then the warranty may be voided the way you have connected it. And not compliant with bs7671 as not in accordance with manufacturers instructions.

 

[topquark]

What purpose do the valves serve now? If none, suggest they get a plumber to remove along with any external pump, unless it's a v large property with multiple zones.

 

[Meggerman]

What purpose do the valves serve now? If none, suggest they get a plumber to remove along with any external pump, unless it's a v large property with multiple zones.

It may have multiple heating zones, it may also have a hot water cylinder. This is quite common having water cylinder for bathrooms and the combi side for kitchen & utility.

 

[topquark]

Really? Multiple zones eh?

 

[7029 dave]

It may have multiple heating zones, it may also have a hot water cylinder. This is quite common having water cylinder for bathrooms and the combi side for kitchen & utility.

That's news to me, never seen combi setup with hot water storage, take your word for it.

 

[topquark]

That's news to me, never seen combi setup with hot water storage, take your word for it.

Does happen. Just another zone really. Done when you want a decent power shower with separate pump, as you can't run that off a combi.