n/a - Importance and value of diagnosis and experience

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Wed 14 Jan 2015 18:55
n/a - Importance and value of diagnosis and experience - Andrew-T

Just successfully completed a fix to my central-heating Combi boiler. After many years reliable running, I noticed very high readings on the pressure gauge. Summoned respected local plumber, who hadn't had this problem before, so rang the makers.

Could be a blockage in a connecting pipe, so removed and checked, OK; also the diverter valve. Next idea was a failing diaphragm in the pressure vessel, so that was ordered and fitted, which required other dismantling just to get it out and back in. Working pressure still up over 3 bar.

Finally decided that the small heat-exchanger had an internal leak. Replacement fitted today, and problem solved. Plumber (many years experience) said he had never fitted one before, but his mate did one once. I await the bill with interest. Still, the boiler (14 years old) has been virtually rebuilt, so should run for years. And there is more heat in the radiators ....

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Wed 14 Jan 2015 19:25
n/a - Importance and value of diagnosis and experience - gordonbennet

Our heat exchanger sprung a leak about 3 years ago, and our handy boiler specialist chap fitted a new one.

More heat and faster warm up now, boiler's about 22 years old now and so long as it keeps going it can stay there.

Maybe it's something worth getting done @ around 10 year at typical half life even if there's no apparent symptoms but the system isn't doing its job quite as well as it once did.

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Wed 14 Jan 2015 23:04
n/a - Importance and value of diagnosis and experience - Andrew-T

It appears my boiler dates from 2000, so it is doing quite well. Another symptom of the problem was increased water usage by about 50% - there was continual escape from the external overflow.

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Fri 16 Jan 2015 17:08
n/a - Importance and value of diagnosis and experience - concrete

Just a query Andrew. I would have thought that a leak in the sysyten would reduce the pressure. After the system is filled, vented and pressurised to about 1.5 bar the filling loop should be isolated at two points to prevent it pressurising the system up to mains pressure. Which means you have a sealed system: ergo a leak is pressure loss and the boiler would go into Lockout mode. This can also occur when if you ever vent a radiator, the pressure drops, Maybe your filling loop developed a fault and was passing and pressurising the system, which would release pressure through the relief valve at 3 bar and above, which would discharge outside through a 15mm copper pipe. Too late to identify that as the main fault and you have a lot of new parts to rely on in future, but it is worth getting a new filling loop fitted, one with two isolating valves and a non- return valve combined.

Good luck.

Concrete

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Sat 17 Jan 2015 12:49
n/a - Importance and value of diagnosis and experience - Andrew-T

Concrete - thanks for reply. Two points: the boiler is a Combi, and our mains pressure is over 3 bar. The plumber - who I trust - reckons that both the ballast vessel (which absorbs volume changes with temp) and the pre-heat exchanger were faulty. He demonstrated the internal leak in the H/E by blowing into one circuit with the exit blocked. Anyway, changing the H/E sorted the problem.

After his first 'fix' - the ballast vessel - there seemed to be no improvement, as the system pressure rose to >3 bar within minutes. Clearly (with hindsight) the system was effectively connected to mains via the H/E.

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Mon 19 Jan 2015 17:39
n/a - Importance and value of diagnosis and experience - concrete

Hello Andrew, got it now. The problem was on the domestic side of the circuit not the heating side. Hope your fix works well. Good luck. Regards, Concrete

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