Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators. It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil. I can't see any way, but there are two air vent valves on
the inlet and outlet. They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...BEgKf4_ D_BwE

....or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight. I think it
should be loose. Should it?

Cheers
--
Clive

On 10/02/2018 20:41, Clive Arthur wrote:
Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators.Â* It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil.Â* I can't see any way, but there are two air vent valves on
the inlet and outlet.Â* They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...BEgKf4_ D_BwE


...or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight.Â* I think it
should be loose.Â* Should it?

Cheers
Yes, on ABVs the caps should be loose, but it's highly unlikely to be
air in the coil. If the problem really is only present with hot water on
then it might be the zone valve or some other valve rattling, or a tap
jumper rattling if the it isn't completely off.

Clive Arthur wrote:

Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators. It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil. I can't see any way, but there are two air vent valves on
the inlet and outlet. They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...ltecnic-valves
-c421/altecnic-caleffi-robocal-bottle-air-vent-p9592/s9594?utm_source=goog
le&utm_medium=cpc&utm_term=altecnic-caleffi-robocal-bottle-air-vent-15mm-1
5mm-15mm-502649&utm_campaign=product%2Blisting%2Bads&gclid= EAIaIQobChMIova
q7Zec2QIVzrXtCh1MZgwIEAQYBCABEgKf4_D_BwE

...or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight. I think it
should be loose. Should it?

Cheers

Yes, the button should be turn and a half or so open to let out air.
But don't leave them open after all the air's gone. In theory that
should be a good idea, but in practice they get gummed up with
limescale, leak water and don't let air out any more if you leave them
open too long.

--

Roger Hayter

In article ,
writes:
On 10/02/2018 20:41, Clive Arthur wrote:
Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators.Â* It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil.Â* I can't see any way, but there are two air vent valves on
the inlet and outlet.Â* They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...BEgKf4_ D_BwE


...or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight.Â* I think it
should be loose.Â* Should it?

Cheers
Yes, on ABVs the caps should be loose, but it's highly unlikely to be
air in the coil. If the problem really is only present with hot water on
then it might be the zone valve or some other valve rattling, or a tap
jumper rattling if the it isn't completely off.

Or insufficient flow through boiler so it's kettling or boiling.

BTW, ABV's mustn't be left open, or they will form hard water scale
on the seal, and then fail to seal and leak water.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 10/02/2018 23:06, Roger Hayter wrote:
Clive Arthur wrote:

Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators. It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil. I can't see any way, but there are two air vent valves on
the inlet and outlet. They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...ltecnic-valves
-c421/altecnic-caleffi-robocal-bottle-air-vent-p9592/s9594?utm_source=goog
le&utm_medium=cpc&utm_term=altecnic-caleffi-robocal-bottle-air-vent-15mm-1
5mm-15mm-502649&utm_campaign=product%2Blisting%2Bads&gclid= EAIaIQobChMIova
q7Zec2QIVzrXtCh1MZgwIEAQYBCABEgKf4_D_BwE

...or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight. I think it
should be loose. Should it?

Cheers

Yes, the button should be turn and a half or so open to let out air.
But don't leave them open after all the air's gone. In theory that
should be a good idea, but in practice they get gummed up with
limescale, leak water and don't let air out any more if you leave them
open too long.

Thanks all, that seems to have worked. I'll close them now.

Cheers
--
Clive

On 11/02/2018 09:34, Andrew Gabriel wrote:
In article ,
writes:
On 10/02/2018 20:41, Clive Arthur wrote:
Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators.ÂÂ* It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil.ÂÂ* I can't see any way, but there are two air vent valves on
the inlet and outlet.ÂÂ* They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...BEgKf4_ D_BwE


...or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight.ÂÂ* I think it
should be loose.ÂÂ* Should it?

Cheers
Yes, on ABVs the caps should be loose, but it's highly unlikely to be
air in the coil. If the problem really is only present with hot water on
then it might be the zone valve or some other valve rattling, or a tap
jumper rattling if the it isn't completely off.

Or insufficient flow through boiler so it's kettling or boiling.

BTW, ABV's mustn't be left open, or they will form hard water scale
on the seal, and then fail to seal and leak water.

That's interesting. I've always left them open and not had a problem
with scale, but I take the point.

Clive Arthur wrote:

On 10/02/2018 23:06, Roger Hayter wrote:
Clive Arthur wrote:

Our pressurised central heating boiler is making rattling/banging
noises, but only when the hot water is on but not the radiators. It
sounds like air in the system; all the radiators are bled.

So I wondered if there was a way to bleed any air from the hot water
tank coil. I can't see any way, but there are two air vent valves on
the inlet and outlet. They look a bit like this...

https://www.jtmplumbing.co.uk/heatin...ltecnic-valves
-c421/altecnic-caleffi-robocal-bottle-air-vent-p9592/s9594?utm_source=goog
le&utm_medium=cpc&utm_term=altecnic-caleffi-robocal-bottle-air-vent-15mm-1
5mm-15mm-502649&utm_campaign=product%2Blisting%2Bads&gclid= EAIaIQobChMIova
q7Zec2QIVzrXtCh1MZgwIEAQYBCABEgKf4_D_BwE

...or even...

https://goo.gl/2ctbUC

On ours, the plastic cap/button is screwed down tight. I think it
should be loose. Should it?

Cheers

Yes, the button should be turn and a half or so open to let out air.
But don't leave them open after all the air's gone. In theory that
should be a good idea, but in practice they get gummed up with
limescale, leak water and don't let air out any more if you leave them
open too long.

Thanks all, that seems to have worked. I'll close them now.

Cheers

I suppose the limescale problem is actually going to depend on your
local water hardness and on how well inhibited and leak free your CH
system water is. I can only speak from my experience, but I note others
say they leave them open!


--

Roger Hayter