Brian Reay wrote:
"Tim" wrote in message
m...
Chaps hi,

hoping for a bit of advice here. I have recently moved house to a
property which was built circa 1987. One item picked up on the
survey was that when the bolier came on (ch or hw) it made lots of
loud
banging noises. So it has been doing this for at least 6 months

This didn't bother us too much but now we have started to use the CH
with the onset of winter it is waking us up every morning with a
*very* loud BANG. Having recently had the old analogue programmer
fail (and having to update it and the thermostat myself) I have
decided that it has to be worth an attempt at self diagnosis - and
then possibly trying to fix it myself or get some one in.

I have looked through similar posts but was hoping that this might
make sense to someone out there.


Two ideas spring to mind:

1. Air in the boiler- especially if the neither of the water pipes
exits the boiler at the top and continues 'up' . (If they don't, air
can get trapped in the boiler and it will stay there- in the extreme
enough can collect to stop the boiler lighting.) There is (usually)
a bleed valve in the boiler at the top of the heat exchanger.

2. Is the pump starting up reliably? If it 'sticks' the water in the
heat exchanger could be boiling, making the 'bangs' and the shock
kicks the pump to life.

I had the same problem a few years ago - very loud banging noises whenever
the heating fired up. The British gas solution to the problem was an offer
to relieve me of £2200 for a new boiler etc. My solution was to drain
absolutely everything containing water, then to flush the heating system
with Fernox, and then fill with Fernox inhibitor. The problem must have
been an airlock somewhere in the system. I then had a worrying time when I
lost the shower and all hot water, but I persevered and got it all working
eventually. This was over two years ago and it's still working fine.
Central heating is really somewhat of a black art and problems take time to
solve. Unfortunately the professionals don't take the time - you couldn't
afford it if they did. For example, a full heating system balance could
take a full day - would you be prepared to pay for this? - this is why it's
never done properly unless you DIY.

Terry D.