Will This Alteration Mean I Can Run HW & CH Seperately?

[3500P5BV8]

Untitled

• 3500P5BV8
• 2 Mar 2010
• 1

Above is the system I have at present. Concorde WRS boiler, fully pumped, a single 2-port valve controlling the heating, a room stat and Potterton EP3002 programmer.

I can have the HW on on its own, but if I have the CH on, the HW also has to be turned on.

The diagram below shows the lives from the programmer. Would it be OK to run a new link wire from the switched live of the room stat to power the pump and boiler when the CH is on?

This would mean that I can have seperate control of CH and HW on the programmer, and won't have to have the HW on to make the pump and boiler run for the CH

Untitled

• 3500P5BV8
• 2 Mar 2010
• 1

(There is no pump overun on the boiler)

 

[stem]

Unfortunately it won't work, in fact it will be worse!

When the hot water is on at the programmer, the live from the programmer to the pump will also feed back to the motorised valve (yellow wire in your diagram) and turn the central heating on as well, and it by-passes the thermostat too, so that will have no control either.

Then, when you have only central heating on, the hot water will also be on, because basically run the pump/boiler and you get hot water.

To do it properly you need to add either a second motorised valve for the hot water (Known as S Plan) or replace the existing motorised valve with a three port valve (Known as Y Plan) for hot water and central heating control. The valves have integral micro switches for pump and boiler control to isolate the two functions.

 

[3500P5BV8]

When the hot water is on at the programmer, the live from the programmer to the pump will also feed back to the motorised valve (yellow wire in your diagram) and turn the central heating on as well, and it by-passes the thermostat too, so that will have no control either.

Didn't think of that. Will buy second 2 port, and change to S Plan.