We have a Worcester 28CDi combi boiler that we had installed approx
7/8 years ago. Last year we had a new heat exchanger fitted. We have been having rouble since Christmas. First we had no central heating and the pressure dial was all over the place, falling and rising, our installer came back and fitter a new pressure loop which then seemed to work ok. We then had trouble again with the pressure dial and leakage from the safety valve, the fitter thought the pressure dial was not giving the correct reaing and therefore the emergency valve blew. He came again and refitting the safety valve. We now have no hot water. When running the tap its warms up to hot and then goes cold. Whilst talking to the fitter on the phone, he suggested topping up the pressure and running the hot water to see if if now worked. Whilst doing this the boiler blew from the top valve with steam. He is suggesting that we might need a new boiler, but this seems to be a bit drastic. Can anyone give us any advice on what they think might be happening and what we can do.
Did he not fit a new pressure gauge, if that's what he thought was dodgy?
Sounds like the heat exchanger blocking up on the primary side. Why did you have the heat exchanger replaced last xmas? And if it was the same problem what was done to stop it recurring?
Sounds like the automatic air vent. What did you raise the pressure to (and how reliable was whatever you were measuring it on)?
Combination of Sod's law, clustering of random events, problems of combis once they get past five years IMHO.
In the past month mine has:
blocked a DHW HX (fixed) failed the ignition circuit on the main board (fixed) split a DHW flow sensor diaphragm (fixed)
and in the course of all that, the auto air vent decided not to seat, so it was dribbling water. Took out the valve and cleaned off the scale mechanically; now it doesn't leak, or vent either. Waiting for a new one.....
Oh, it's a Wickes / Halstead. But the preceeding Vaillant behaved much the same after eight years.
Makes you think about signing up for BG service.....
The new HX and the failed auto vent point to problems with the heating circuit. Possibly a failed expansion vessel then frequent tops up then corrosion then a new HX?
Properly maintained a Vaillant should go 20 years except for the VUW 2xx (Turbo Max non plus [1]) which are only a bit better than a 'typical' low end combi.
ALL combis have pressure vessels and this is one component is the /root/ cause of a sizeable proportion of all combi problems.
[1] black fascia, turquoise knobs , ladder of LEDs.
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.
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.
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