Bleeding CH when boiler is highest point?

[chris1982]

For the last couple of weeks I have been bleeding radiators, but seem to be unable to get rid of a small amount of air that must still be left in the central heating system. I think there is still some air as I hear it gurgling when the boiler comes on.

While I get a little bit of air every day out of a towel radiator in the bathroom (on the first floor), I think I fail to get all the air out since the boiler is actually the highest point of the system (in the airing cupboard on the first floor).

How do I get the air out when it seems to stand in the boiler when swiched off?
Am I missing a trick here? When I bleed the radiators, I always switch off the boiler - should I not? Or could I do some trick with the filling loop? I am out of ideas, so I'd be happy to hear yours.

Just so that you know the air is in the system since a new radiator was fitted. I don't think there is a leak, as the pressure of the system is constant (when not bleeding).

 

[ianmcd]

make and model of your boiler ?

 

[chris1982]

make and model of your boiler ?

Hi.
It is an Ideal Icos.

There is also "something" I don't know on the return pipework, see photo:


Thanks.

 

[gasbusters]

The boiler should have an automatic air vent, check the manual for its location and slacken it slightly if its closed.

You can also try bleeding the pump, gentle turn the large flathead screw on the pump, only slightly. Air may come out, them water. Once water comes out tighten it.

 

[ianmcd]

The boiler should have an automatic air vent, check the manual for its location and slacken it slightly if its closed.

You can also try bleeding the pump, gentle turn the large flathead screw on the pump, only slightly. Air may come out, them water. Once water comes out tighten it.

an Ideal Icos does not have an automatic air vent

 

[chris1982]

Thanks both. So bleeding the pump is the only possibility? How do I do that?

 

[ianmcd]

When you say the boiler is at the highest point do you mean it is higher than all your radiators and your Hot water cylinder ?

 

[chris1982]

Yes, exactly. The bottom of the boiler is about as high as the top of towel radiator, which is after the boiler the next highest point. The hot water cylinder is just below the boiler.

 

[ianmcd]

you will need automatic air vent installed at the highest point in the pipework

 

[chris1982]

Thanks. That wouldn't be DIY though.
If I kept bleeding the radiators, and maybe the pump, would I ultimately not succeed in getting all the air out? The system used to be fine before it was drained and refilled.

 

[ianmcd]

most boilers the flow and return pipes connect from the bottom of the boiler and the automatic air vent AAV is incorporated into the boiler but if you look on the installion and servicing instructions it clearly states that an externall AAV is required and should have been fitted when the boiler was installed, if there is a compression fitting at the highest level you could try slackening that a little and let the trapped air out then tighten it back up, no the air is at the highest level and needs a way to get out

 

[chris1982]

Thanks. When I have some time I will take the boiler cover off and have a look, but sounds like I need to get someone in...

 

[ianmcd]

No you do not take the boiler cover off to do it, it goes on the highest point in the peperwork not the boiler

 

[chris1982]

Ah right. Then I can't do it that way as all pipework below the boiler is soldered. Thanks though.