gas boiler thermocouple

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Andrew Gabriel wrote:

is probably bespoke and may incorporate auto air vents etc.
There are spares for combis that are well over 10 years old readily available.
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Ed Sirett - Property maintainer and registered gas fitter.
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writes:

You just change the pump head, which is standard and available in many local sheds. The Microgenus's pump head appears to be a standard Willo with the body having 2/4 cxns.

Many are just kits with third party components: Grundfos pumps, Honeywell 3-way valve, Honeywell, gas valve, etc.
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Andrew Gabriel wrote:

Once a boiler has had a small water leak for a while the corrosion and associated problems seem to send it on a downward path.
This is a straw poll of the boiler failures for which I have ended up replacing the boiler (often with a Vaillant Turbomax+ 824e).
1) Saunier Duval combi - poor HW perfomance very noisy. about 10 years old. 2) Ideal Mexico - floor standing CI - 25 years old? primary circuit corrosion leading to heat exchanger failure due to indirect coil leakage. 3) GlowWorm Space saver - 22 years old - refurbishment - needed [cylinder] cupboard space. 4) Vaillant VCW combi - abused life of 17 years (lack of maintainance, zero primary pressure etc.) - multiple faults. 5) Vaillant VCW about 12 years old - good order - spaced needed for new kitchen - new boiler to outside cupboard. 6) Glow Worm back boiler - thermostat failure leading to safety notice by fire brigade! - say 20 years old. 7) Ideal Concord - working order - say 25-30 years old - inefficiency. 8) Glow Worm back boiler - inefficiency - about 20 years old. 9) Glow Worm Space Saver - primary circuit corrosion (pumping over) about 15 years old- HE failure. 10) Potterton Profile - serious primary circuit corrosion about 10 years old - HE failure. 11) Vaillant VCW combi - 17 years old, PCB failure - customer chose replacement rather than a repair. 12) Ideal Condord - thermostat failure leading - about 25 years. 13) Thorn Apollo - 15 years? - neede cylinder space and HW pressure. 14) Alde thermal storage combi - (7 kW boiler and heat bank in a box) - poor HW performace and not enough stored energy. - 10 years old.
Looks like a good few of the CI monsters would go on and on until their thermostats would fail provided their primary circuits did not eat them first!
In the nominal 20 year life of the boiler it is likely to burn 2-5 times the cost in gas of its total installed cost
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writes:

In your list the failed boilers, not those that were not suitable for the current usage, would have lasted a lot longer if the system was installed correctly and/or maintenance was carried out at regular intervals. Even so there were many 20 year olders despite the abuse.
A well designed system with a condensing spiral tubed heat exchanger, top mounted burner, with the air intake in clear air rather than in a position to drag in excessive dust, will last a hell of a long time. The condensate washes down the heat exchanger cleaning it. A modern boiler that analyses combustion would last even longer as if the boiler was out of tune it would lock out.
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writes:

What are the classic installation errors ? And as to maintenance - I've watched what gas fitters do - you're lucky if you get more than a quick clean and a gas analyser shoved in. What is the important maintenance ?
Incidentally, you talk of reliablility, one of the electronics engineers here ended up modifying the board in his boiler because the b*stard blew up every year and cost him over 100 quid to get fixed - cant recall the make........
Steve
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writes:

Undersized pipes. Filing loop left permanently connected topping up the system with fresh water constantly. Over-pressurised system. Under pressurised system. Having rad valves on all rads and no pressure differential valve fitted, which means no flow through the heat exchanger. Some boilers now have these as standard inside the white box. Mains water pressure too high with no pressure reducer fitted. No anti-scale devices fitted in hard water areas such as phosphor canisters, or electronic devices. Some boilers have anti-scale incorporated. Because of the poor installations some makes have incorporated functions to eliminate/reduce poor fitting and promote longevity. These are the models to DIY.

Keeping the system pressure up for one. If it is down, why is it down? Setting up the gas pressures and the analyser too.

geoff will tell you about boards on boilers. There are 100s of them. Some good, some bad.
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sro wrote:

Of the straw poll list. The number one avoidable problem would have been correct primary circuit layout to reduce air ingress. On the sealed systems it would have been maintaining primary pressure.
Hardly any of the boilers (that I took out) died due to poor maintenance as such.
In fact a significant cause of death was being inefficicent (2) or being conventional when they should have combi(>3).

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writes:

I think you and I agree here, my experience is that old simple boilers cause me far less trouble. I have recent experience of repairing a combi :-(
I also suspect that fitters like combis because it makes installing a heating system easy for them. The plumber that used to rip my girlfriend off when her combi gave trouble did admit to her that "he loved them" - very good for business :-)
Steve
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writes:

What went wrong? See my post on this thread of system v system.

There is that., and it is cheaper for the customers too.

Well as about 60-70% of all boilers being fitted are combi's then they are good for business.
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filling loop valve leaking so system allways being topped up pressure vessel diaphram split the dump valve jammed open
It was my girlfriends house. Not sure what caused what because the friendly corgi bloke had been round a few times to "sort out problems" - I'd guess that was the boiler switching off due to low pressure. I reckon he charged the big callout fee to just re-pressurise and hit the reset button......
It was the first time I had seen a combi - I was lucky that the pressure vessel change on that model was easy, apparently some of them make this really awkward.
My house has a very old and simple back boiler and I dread the day I have to replace it because everyone I know with a modern system has loads more trouble than I've had in the last 18 years. In addition, as with most things, manufacturers try to make money by the servicing, so devices are designed to be non-user servicable. Just look at cars - main dealers charge close on 200 quid for little more than an oil change in the south east...... If I could buy the same old fashioned boiler again I definitely would.
Steve
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The filling HAS to be disconnect - not a fault of the system.

Could have been caused by the filling lop always being connected

Debris. in-line stainers can solve that.

Old boiler designs are very inefficient. See the thread on the Potterton combi too. If you buy a quality product and have it installed correctly then you will expect 20 years from it.
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Yes I know that efficencies have increased although I do take issue with the way the plumbing/heating trade love to quote "efficiencies" of more than 100% without explaining the particular scam they are using to break the laws of thermodynamics.
I will probably install it myself when the time comes and will follow best practices along with trade advice ( luckily I do have access to this ). As to 20 years - yeah right, just like quality cars dont go wrong if properly maintained - check out my pitch for "most boring bmw rants" in the uk.rec.cars.maintenance :-)
I reckon I'll get more trouble, which I'll deal with, but I will be very interested to check out the claimed efficiency increases - according to the sedbuk scales a modern boiler should be double the efficency - I'll be interested to see how that translates into quantity of gas used.
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What would you define as 100% efficient? Let's suppose you define it as a condensing boiler whose flue gasses are at the same temperature as its air intake. Now I come along and invent a scheme for recovery of the latent heat of fusion from the condensate (i.e. this boiler spits out ice cubes instead of a dribble of condensate). So my boiler is now 120% efficient according to your scale, but I didn't break any of the laws of thermodynamics.
Now just hang on whilst I nip off to the patent office...
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wrote:

First the good news: Every pub will want one
Now the bad news: If you think pluming is a nuisance just stand under one of these flue outlets!
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Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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Andrew Gabriel

I expected pubs to have one already, if they only connected it to the condesate drain. It's the dry ice maker they want.
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Andrew Gabriel

In Germany all flues are taken through the roof. Few flues are taken through walls.
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writes

true in my experience
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Andrew Gabriel

Have a look at a new German house.
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"IMM" wrote | > >In Germany all flues are taken through the roof. Few flues are | > >taken through walls. | > Apart from the obvious fault in the above, I'd say that's not at all | > true in my experience | Have a look at a new German house.
What about a new German flat? There are far more flats in Germany (59%) than in Scotland (38%) or England (19%) (from housing.odpm.gov.uk)
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And the flues still go through the roof.
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