S-plan system 4 valve system. Hot water to activate when any one is activated.

[Steve19861989]

In a 4 motorised valve system, how can I have the hot water valve activated not only when that valve is specifically powered but is also activated when any one or more of the other valves is activated while at the same time allowing the hot water valve to close when the hot water has reached the desired temperature? So, as an example, If A, B and C are motorised valve for central heating zones A1, B1 and C1 respectively and D is the hot water motorised valve controlled by a cylinder thermostat, it is desired to

1 activate D so that none of the other valves A, B or C is activated; or

2 activate A (or B or C) so that the hot water valve is also automatically activated which will close when the hot water reaches the required temperature; while

3 valves A or B or C can function independently.

Thanks.

 

[Madrab]

S plus system -

Understand how an S plan system works - The programmer calls for either CH or HW or both - That call then travels to the CH or Cyl stat - if they are also calling for heat then the power heads to it's valve - that valve opens and closes a switch that then sends a switched live to the boiler to turn it on.

(edit) The controlling factor are the stats. The rest is just wiring and power. You just need to ensure that the programmer (power) is always calling for both and then the valves are controlled by the stats (powers the boiler). In essence you would have the programmer always on for everything (or always off) and the individual stats then control when each zone/HW runs .

 

[stem]

Wire the coils of three relays with normally open contacts to N & L of the three central heating motorised valves A, B, C.

Connect the normally open contacts of the three relays together in parallel.

Connect one side of the normally open contacts to a permanent live

Connect the other side of the normally open contacts to the 'HW On' of the programmer.

When any of the CH valves are opened, the relay will also switch on the HW. The relays provide the necessary isolation between the motorised valves.

For the purposes of the diagram I have assumed that the grey wire to the motorised valve is the permanent live. Convention states that's the way to do it, but very occasionally some installers transpose orange and grey. So best to check first.

 

[stem]

@Steve19861989 just wondering how you got on with this?

I forgot to mention that with my suggested solution, connecting the wire to the HW On terminal (instead of the motorised valve D as you suggested) means that the hot water cylinder thermostat will still function and prevent the hot water overheating. Although you might not have noticed so far, as I imagine you don't have the central heating on at the moment.

 

[Steve19861989]

@Madrab Thank you and with apologies for the delay in responding.

@stem Thank you and with apologies for the delay in responding. I have not as yet been able to implement your suggestions but will report back when it is completed. I may not be able to do so for a few weeks.

 

[Steve19861989]

@stem. I have now installed the 3 relays as you suggested. Two of them work as is desired. In other words, when power to, for example, Zone A or Zone B vlaves is switched off, then the boiler/pump also switches off. However, for Zone C, there is a "problem". Having turned on Zone C, its valve opens as does the HW cylinder valve. However, when Zone C is powered off, the boiler pump continue to operate and will only switch off the the HW thermostat reaches the desired hot water cylinder temperature. In other words, power is constantly applied to the Zone C's relay. I hope that makes sense. If you have any thoughts on this, please let me know. Otherwise, I'll abandon the Zone C relay option. Thanks again for your advice.