Banging Boiler

[john east]

A year ago we had a worchester Ri boiler fitted on the wall in our kitchen
diner. It's always made a bit of a banging noise. Not every time, but
really quite often; usually just after it turns itself off, after the boiler
being on for a bit.

We have just had our first annual service. The chap never even opened the
boiler, but just fed a meter tube into the top of it and he also watched how
fast the gas was going out of the gas meter.

I asked him about the banging. He asked if the rads had been bled recently
and I confirmed that they had. Since it was suggested to me that this might
be a cause of all the rucus. After looking in the water cylinder cupboard
he told me I needed a 'by pass' or a 'mixer valve', but looking at it he
wasn't sure where the by pass pipes would be connected.

Are these 'by pass' and 'mixer valve' not items that should have been put in
when the boiler system was installed last year?

[NT]

Banging after switch off is known as kettling. The water in the boiler
exchanger boils. The 2 solutions are to increase pumping speed, or to
add an overrun timer (or repair broken one.)


NT

[charles]

In article
<4e9c021e-f516-4b34...@e15g2000vba.googlegroups.com>, NT

one further cause is sludge getting to the boiler. This was suggested to me
a month or saoa go, on this newsgroup, and since flushing out the system I
have had to futher recurrence of the problem.


> NT

--
From KT24

Using a RISC OS computer running v5.16

[RobertL]

On Nov 16, 3:26 pm, charles <char...@charleshope.demon.co.uk> wrote:
> In article
> <4e9c021e-f516-4b34-aa0f-3a60853d3...@e15g2000vba.googlegroups.com>, NT

I had a banging noise from my Vokera boiler, as if someone was banging
on the case with a gloved hand. it would do it for a bit, then it
would reset.

Eventually we found that the balanced flue pipe had come apart in the
loft!

Robert

[harry]

On Nov 16, 1:47 pm, "john east" <planet...@mail.invalid> wrote:

What the man told you is essentially correct.
Local hot spots in the boiler let the water boil and what you hear is
stem bubbles collapsing as they cool. (Cavition)
There is a minimum water flow through your boiler, if you go below it,
local hot spots can appear inside the boiler.
If the boiler is piped up "traditionally" as the thermostatic radiator
valves close, water flow is reduced through your boiler which can
cause this problem.
If the pumpis on the return side of the boiler, it reduces water
pressure inside the boiler exacerbating the problem.

The solution is to fit a spring-loaded "bypass" valve which is opened
by the rise in pressure as the thermostatic rad. valves close, so
keeping water going through the boiler.
Example here.
http://www.screwfix.com/p/honeywell-straight-auto-bypass-valve-22mm/34127

It will also let your TS rad valves function better.

[ARWadsworth]

Is it an S Plan by any chance?

<http://wiki.diyfaq.org.uk/index.php?title=Central_Heating_Controls_and_Zoning#CH_and_DHW_zones:_S-plan>



--
Adam

[JohnW]

I had a new Worcester 24ri fitted a couple of years ago and specified
an auto bypass valve to be fitted. After installation I got the same
banging as you and on further investigation realised the valve was
never opening as the adjustment was incorrect. So effectively it was
like your installation. After adjusting the valve no further noise.

John