loud banging after boiler fires up

[davep]

Ive read most of the earlier comments which give some good tips / hints to follow
eg sludge / boiler overun thermostat / air blocks etc .
Most of these problems seem to be with boilers which cut out & restart.

My problem seems to be solely banging so I wish to prioritise whether sludge removal / thermostst or other action is the best action to start with.

All radiators working ok
Hot water ok
All radiators bled & checked
Once clock timer has activated there is approx 30 sec delay before series of very loud bangs .( sound as if they come from airing cupboard )
After 30 secs - 1 minute they will stop .
Recently they have gone on slightly longer , less frequent for another minute ( a bit like after shocks following an earthquake )
Thereafter the central heating works fine . No more bangs until the timer clicks in next.

With two young children ( inc 7 day baby )and the heating required to come on at 6.00 ,there is a lot of lost sleep .

Appreciate comments as to best solution

Boiler is a Glow worm Fuel Saver MK 2 Approx 12 years old . Originally situated in an integral garage with vertical feed & return . When garage was converted into room the boiler was relocated to the utility so there is now 3 metres horizontal pipe leaving top of boiler > If relevent please advise

 

[ChrisR]

If airaccumulates n the boiler it sounds like it can't get out too easily. Once a boiler has some scale in it the water will boil under the scale and produce bubbles from the air/gas dissolved in the water, if there is any. If the boiler starts up with air in it then it might overheat - boil and bang. The gas as you know could be hydrogen from corrosion.

So you could do some or all (not expensive) of
put some boiler descaler in (can stay in)
put some inhibitor in
put an automatic air vent on the flow pipe from the boiler

I think the last measure will be the most effective.

 

[boxster]

It is 100% AIR. try pulling the stat or a simple drain down and re-fill might fix it. Also the pump ALTHOUGH working could still be the cause, I bet if its not ait its the pump. Apollo boilers are the main boiler for this

 

[davep]

Thanks Guys

I have noted that the pump does not kick in for what seems like 2 minutes

Is this normal / easy to alter .

Once pump running problem goes . Guess air then vents out of system .

I will drain down once we get a nice day . Any comment re pump delay

Thanks