I have a worcester bosch 24 cdi fitted by BG a few years ago, now I am
having a problem, when I run my shower it goes from hot to cold then
hot again so on & so forth. does anyone know why this is happening.it
does not happen when I run the taps although the flow from the bath
hot tap is quite slow.
any help would be greatly appreciated, before I get someone in to look
at it I would like some idea of what is causing it. so i dont get
ripped off as usual .
If the bath tap is fine, then I'd eliminate the possibility of a faulty
shower mixer before suspecting the boiler.
The bath tap is likely to be slow, as it appears that the installer
correctly backed off the hot tap isolator to prevent you drawing more water
than your combi can supply. A 24kW combi won't provide a high flow rate and
will not fill a bath quickly.
Depends what you mean by slow. If you live in a hard water area then
it's likely that the heat exchanger in the boiler is scaled up which
reduces the flow rate. If it gets too slow the boiler will cut out
periodically and you will find the shower goes cold.
I've heard that it's possible to descale the heat exchanger but don't
know if this is easy or effective. Certainly it won't be cheap to replace.
I tend to agree, some people beleive that electromagnetically conditioning
the water prevents the build up of scale. I don't beleive that so I don't
fit any. The only sure way to feed softened water to the CW inlet of
Some models of boiler are fairly simple to replace the [secondary] heat
exchanger. (The vokera Linea serie is one, the Vaillant turbomax series is
not too bad either. Some are very difficult the floor standing Worcesters
There is a small risk that descaling the unit will spring a leak, but if
you are really looking to save then removal and acid descaling should work
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.