We have a Worcester 28CDi combi boiler that we had installed approx
7/8 years ago. First we had no central heating- the pressure dial was all over the plac=
e, falling and rising.

The pressure dial rising abnormally when the central heating is on and also slowly re=
ducing in pressure over time (so that you have to top up the water pressure via the fill=
loop more frequently than normal) are clues that may infer that the diaphragm in your=
expansion vessell may have failed.

Pressure in my 28cdi used to sit around 1 bar and would rise slightly when the central h=
eating was on.
Over time the boiler would need topping up with water fairly infrequently- when the b=
oiler was new and working properly.

When the diaphragm in the pressure vessell failed, the boiler =

pressure dial behaviour subtly changed. It would rise far more than normal going fro=
m 1 bar prior to the central heating coming on, to 2-3 bar in operation.
Also the water pressure in the system whilst not in operation, would slowly reduce ov=
er time- the boiler would have to be topped up with water via the feed in loop far more fr=
equently than normal.
These changes are subtle and could be overlooked if your system is working ok.
When the pressure vessel diaphragm fails your system will go on working as normal and=
it is difficult to see anything is wrong
other than a change in pressure dial behaviour.

So your boiler will appear to work as normal, with an erratic pressure dial until anot=
her component suddenly fails. =

i.e loss of hot water.

We now have no hot water. When running the tap it warms up to hot
and then goes cold.

The above sign may indicate a common failed component- the diverter valve. The diaph=
ragm in the diverter valve perishes leading to failure of the valve- hence no hot wate=
r, luke warm water or hot water then cold.

Other key components of a combi system are the heat exchangers.

In the 28cdi there is a plate heat exchanger on the hot water on demand circuit. Water p=
asses through this exchanger to acquire heat.
If your water isn't getting as hot as it used to this component may need cleaning or rep=
lacing. They are designed to last 5 years.

Also this boiler has a primary heat exchanger (Gas to water).

This exchanger should last 10 years, so is probably ok in most peoples systems.

If your boiler is behaving irrationally it may have one or more faulty components.

Your pressure dial gives an indication of overall system health.

I watched its behaviour change over time and informed the =


Worcester Bosch heating engineer- this observation helped =


diagnose a faulty expansion vessell. =


This fault was present on my boiler at the same time as a =


faulty diverter valve ( We had lost hot water through our taps).

Many people are now throwing away perfectly good combi boilers =


(along with their own hard earned cash) when they dont need to.


A little self education and observation about your boilers =


operation, helps to diagnose early issues your boiler may have

Learn what your combi boilers pressure dial is for and how to make =


sure it is kept at the correct pressure.

Learn to watch it periodically because it will change its behaviour =


when certain issues arise.


Get your boilers serviced regularly- to prolong boiler life. =



If all else fails and you think your Worcester Bosch boiler has =


problems, call the experts out (Worcester Bosch) or find a good =


researched local independent gas safe service engineer that fixes =


your boiler type on a frequent basis.

A little observation and a little work go a long way in life and =


could save you =C2=A3's.

Look after your boiler and it will look after you.

url:http://myreader.co.uk/msg/1391140957.aspx