Breather Valve?

[hedgert]

My central heating system has recently started letting dramatically more air into the water system. I need to bleed the upstairs radiators at least weekly now to ensure the top part of the tallest couple of radiators remain hot. Looking back, I used to bleed every few months - and then only let a small amount of air out.
I notice this (see picture) on the towel radiator in one of the bathrooms and wonder if this is some kind of breather valve - that has maybe stopped working? Can anyone advise what it is/what it is called?

 

[rochdalegas]

Ive never seen one like it im sure someone on here will have though. You would assume its an automatic air vent just a nicer looking one than most as it is in show.

 

[Newboy]

If you're having to bleed the system every week then you need to find out where the 'air' is coming from. If you have an open vented system then air is possibly being drawn in or the system is corroding (badly) and producing gas.

Either way, that much air in the system is bad news and needs to be checked out before your rads rot away.

 

[Nige F]

Ive never seen one like it im sure someone on here will have though. You would assume its an automatic air vent just a nicer looking one than most as it is in show.

I've never seen one either - it's above the manual air vent fitted in the factory. Looks like it's been turned in a lathe and brazed into the towel rail - probably by an engineer- certainly not by a heating engineer/plumber. Newboy is spot on in his comments.

 

[Wildcat1961]

It’s a glorified ‘Aladdin’ air vent.
Any moisture detected will close the vent, when the moisture dries the vent will open.
A crude description of the working principle being a paper element.

 

[John D v2.0]

Is it a sealed system (with a pressure guage and braided filing loop, and a metal pipe from the boiler terminating outside) or open vented with a small tank in the loft?
If it is sealed, what does the pressure guage say? And is your house 2 floors or 3?