Central Heating Check Valve

[edmdas]

I am fitting a secondary circuit for an extension. I have a Greenstar 42CDi Combi boiler. I want to know if I need to fit a check valve on the return circuit as the new return circuit will run through a T junction with the existing return circuit. I have attached a diagram to hopefully make things clear.
I am worried that if the second circuit is on, but the first circuit is off there will be seepage back to the radiator which is above the pipe work so convection will help heat this rad.
Secondly, given the operating temperature, the distance of the return circuit will the flow / pressure be too weak to operate a check valve? Is there one on the market that will work?
Any advice, experiences would be very helpful!
Thanks

Untitled

• edmdas
• 25 Mar 2012
• 1

 

[Norcon]

As long as there are no return paths from the flow into the upstairs rad back to the primary return then you won't need a check valve.

 

[edmdas]

OK Thanks, but I'm not sure I understand what your asking?

I will have two zones on zone valves for the outward (send) sideof the circuit. If Zone 1 (Return1) is off and Zone 2 (Return2) is on won't there be some back flow up the Return 1 pipe and nothing to stop this going up to the rad?

Or do you think the draw from the boiler pump will prevent this?

Sorry if I seem a bit dim but I'm on a steep learning curve here.

 

[Norcon]

is on won't there be some back flow up the Return 1 pipe and nothing to stop this going up to the rad?

There is no return path therefore no flow. Rad stays cold.

 

[edmdas]

Thank you Norcon, I think I understand now. Appreciate the help very much.