Bridging out 2 port valves

[PlumbBob]

Hi

Trying to work out how my heating is plumbed, why would output of S plan 2 port valves be also bridged by a gate valve (normally shut) ie the heat output from boiler goes to x2 two port valves - one for HW and one for CH, but why provide a means to bypass them?

by the way I have a wood stove too with its own pump - it heats the indirect cylinder but also when pump switches on it heats the same CH - I have no idea how this is plumbed as all pipes are hidden

 

[kidgreen61]

The gate valve is there to act as a bypass, it (should) allow some water to flow through it when the the boiler stops firing, the pump will continue to run, dissipating heat. If it is closed, that won't happen.

 

[PlumbBob]

okay thanks, yes heard of that, should I replace it with some automatic type valve?

 

[PlumbBob]

Showing the 2 port valves bridged, I’m sure this gate valve serves no purpose, and think there should be an automatic bypass between flow and return?

 

[Madrab]

That is in a strange place, it's not acting as a bypass being after the valves. I take it the top pipe is CH?

It may allow a shortcut to the drain valve for the CH system pipework.

 

[PlumbBob]

The top pipe is the HW valve, but yes it could be for draining purposes still.

I’ve learnt the automatic bypass should be between the flow and return and I may change this arrangement now as I need to move it out the way for a new boiler.

 

[Madrab]

Ah, didn't see the 28mm on the valve, the bypass should be between the flow and return, after the pump but before the valves. This allows minimum flow through the boiler on pump overrun, when the valves close.

 

[oilhead]

Could it be designed as a bypass for the wood stove circuit?

 

[PlumbBob]

I was thinking that @oilhead but the stove is 4 port and has 2 pipes running to own cylinder coil (28mm) unpumped and x2 22mm pipes (pumped) running to rads somewhere - I know as rads get warm when pump is running

Yes @Madrab I will plan to do that, so pump is on the return (this is an old system) input to the boiler; so I plan to install an Auto-PRV on the CH flow upstream of the valve - so on valve closure and any residual pressure circulates through the boiler and back around the CH system.