Some radiators on a hot water circuit.

[jobloggs]

I have just fitted a mid position valve and thermostats on an existing fully pumped, vented, oil fired system. Valve is in boiler house close to pump.

On commissioning I have discovered that three radiators on the ground floor extension were plumbed off the indirect hot water circuit and are now controlled by the HW programmer and cylinder thermostat. Cylinder is in the loft 2 storeys up and at other end of building.

My initial thought was to
1 cap the flow and return of this circuit beyond the radiator positions
2 tee the flow into that of the main CH circuit just beyond the mid position valve.
3 Run a completelty new circuit from the MP valve to the cyl coil and back to the boiler.

Then another possibility struck me which would halve the amount of new pipework required. What would happen if I:
1 capped the flow pipe beyond where the rads are teed off
2 teed the flow to these radiators into the main CH circuit just beyond the mid position valve.
3 run a new flow from the MPvalve to the cylinder and used the existing return from the cylinder.

Would there be a problem with this second scenario? If so is it possible to cure with a check valve or is it fundamentally flawed?

Apologies if the above is not very clearly explained.

 

[ChrisR]

I think we aren't gong to be sure what you mean unless you draw it and upload the sketch say to photobucket or similar.
You have to be careful about where the returns come in - the one from the HW has to be last, or you'll get "secondary circulation".