Purpose of a mysterious (to me) valve in my central heating circuit

[KE55]

I'm just learning about plumbing so this might be a silly question...

I was looking at the central heating pipework in our bungalow's attic and noticed what appears to be a manual valve linking the flow and return pipes - see photo below. The valve I'm talking about is the one on the left.

Does anyone know what the purpose of this valve might be?

 

[JohnD]

It looks like a manual bypass.

Do you have TRVs on all radiators except the one in the room with the wall thermostat?

 

[Scarum]

A manual by-pass perhaps?

 

[KE55]

Most of our radiators have TRVs (I think the only exceptions are heated towel rails in the bathrooms). There is also a TRV on the hall radiator where the wall thermostat is located - is that a problem?

If it is a manual bypass under what circumstances would it be used?

 

[Madrab]

It is installed to allow min flow through the boiler and on overrun when the TRV's close down and avoids the pump pushing against a closed system. You now get automatic valves that open and close as required, yours is just a manually adjusted version.

http://www.ferroli.co.uk/news/automatic-bypass-valves-essential-healthcare-for-boilers/

 

[KE55]

Many thanks all for the responses. Now I know what to search for ("manual bypass") I've been able to find plenty of helpful info.

Also my boiler (Glowworm 30cxi) is fitted with an automatic bypass valve so I guess the manual bypass can be left closed.

 

[ianmcd]

Your towel rails will act as a by-pass anyway as they never shut down if no TRVs fitted so you can safely close this valve but as with all valves screw it till shut then ease back off again about a quarter turn it takes the strain off the valve

 

[Aquaheat]

but as with all valves screw it till shut then ease back off again about a quarter turn it takes the strain off the valve

Really? Think you are thinking about opening valves. A positive shut off is just that. back it off and it can start passing, however small. Backing off when open stops the valve from seizing in the seat and being unable to shut off but still requires movement every now and again.

Jon

 

[Gas2Air]

Why are the gate valves on the flow and return would by question.

 

[KE55]

Apparently the valves on flow and return allow the radiators at one end of the bungalow to be isolated.

 

[Gas2Air]

Apparently the valves on flow and return allow the radiators at one end of the bungalow to be isolated.

Why?

 

[dilalio]

Apparently the valves on flow and return allow the radiators at one end of the bungalow to be isolated.

Why?

Torture for a previous, unwanted guest: grandma?