Bleeding the system with a combi in the loft

[IanF]

Hi,

I'm moving a rad at the weekend and will be draining the central heating system beforehand.

When I refill it I know I need to use the fill loop to get the pressure up to 1.0 to 1.5 bar and then go around the rads bleeding the air out of them and repeat until there's no more air in them.

What I'm not clear on, is what to do with the boiler (A Worcester Bosch Greenstar 28i Junior). As it's in the loft it's the highest point in the loop, so will it or its pump also need bleeding? Or is it able to auto-bleed in some way?

I've found a manual online with an exploded diagram on pages 7 and 8 which might help (link).

Any help or pointers appreciated

Cheers,
Ian

 

[lightning]

Boiler will have an aav so no need to worry

 

[45yearsagasman]

What about venting the main heat exchanger? I recall that it has a manual vent and that requires removing the casing. Just saying.

 

[polesapart]

I'd suggest running it for a few short bursts on the lowest possible heat setting for the first few minutes until any gurgles stop. Shorts bursts as in switch off as soon as the burner light comes on.

There is a manual bleed point on the HX as well as the AAV on the pump; I've never found any air there after doing as above.

 

[polesapart]

Pete is of course right; I was trying to suggest a reasonably safe workaround.

 

[BigSnoopy01]

just run it with the gas turned off to stop it firing up. best to fit a pressure guage and filling loop in a cupboard in living area as the juniors system pressure needs to be kept an eye on when at the top of a system as they can dry fire and damage/ripple the hex.

 

[IanF]

Thanks very much for the tips and advice. Fortunately there is a pressure gauge on the landing which makes keeping an eye on it a bit more straight-forward

I've managed to get in touch with the installer and he's confirmed that it's self venting.

Cheers,
Ian

 

[IanF]

Just thought I'd come back and confirm that it did self-vent when switched back on. Completed the job on Saturday morning with no issues.