Automatic By-pass Valve

[plumber0808]

It was a Warmfront installation, of which they fitted a Bypass valve on every job, regardless of what was on the system. Isars did not have a built in bypass. It must be that as that was the only time a Isar was fitted,when it was free.

 

[dancinplumba]

it is in the boiler mi's wether a abv is installed or not

 

[lame plumber]

warter expands when hot if the rad valves close or thier is a loss of powerfor whatever reason and the pump stops suddenly then that expanded warter has nowhere to go that is the purpose of a a b v it is a protection device for the pipework and associated fittings

reread your text books

 

[lbp plg & htg]

So if there aren't trv's on then there isnt any need for it??

 

[Dotty]

So if there aren't trv's on then there isnt any need for it??

Don't get hung up on the trv's alone. What if you have zone valves and pump overrun?

 

[lbp plg & htg]

No ext zone valves or cant see any? Its a combi so I cant recall seeing a combi installation with one in and how would pump over run affect it Croppie?

 

[Dotty]

Trv's and zone valves are automatically operating.

Say for example you have a system with all trv's and no zone valves. The building comes up to temperature and all the trv's close. The pump is pumping against an increased head pressure.

Same with zone valves and pump overrun. The valves will close, shutting down the boiler, when the building's up to temperature. Pump overrun is in operation, again against an increasing head of pressure.

The abv gives the pump a route to pump around without affecting the overall heating efficiency.

 

[Dotty]

And we're talking scenarios, not specific installations!

 

[lbp plg & htg]

Dont worry, me head bang wall!

So flow immediately (500mm) from boiler has t, 1 route is system and the other to abv then into return of boiler. So the trv's, wheelheads, room stat shut down. Does the water not just flow round the system pipework which could be 30/ 40m run?

 

[Dotty]

Think about what you've just asked.

Where is the loop at the end of this 30/40m run?

 

[lbp plg & htg]

yeah but no but!

If it hits the last rad or any others with l/shields on does/ will it not flow through THAT rad and back to the boiler?

 

[Dotty]

IF you have a system with no zone valves and one radiator with no trv's, just lockshields then yeah, it will take the easiest route.

But the that's not what you originally asked lol

*croppie reaches for his gimp slapping stick*

 

[lbp plg & htg]

So Im right in thinking my/ the job I went to doesnt need this valve.

Thanks Croppie for your patience, btw is that the hardest you hit?? ;-0

 

[stevetheplumber]

sounds like warmfront had a blanket policy of fitting a abv on every instal to ensure it was there if needeed shame they didnt spend the money on decent boilers and pay blokes a decent rate to get properly installed work im sure there were some excellent fitters on these schemes and they all get tarred with the bodger brush but every warmfront boiler ive been to is a dogs brekfast
it has nothing to do with exspansion of hot water

 

[gpbeck]

Nothing to stop the customer turning radiators off either.

Why do you think the bypass is noisy? Is this always - high pressures in system? Return temperatures will be higher.