Building Regulation - New Boilers.

[Ed Sirett]

Obviously there are things you can deduce easily. Like the larger consumers (but not so large they use abnormally sized and expensive boilers) have more to gain that the smaller users.

I think that there is not a lot to choose between the reliability of modern condensing and non-condensing boilers. If anything the more corrosion resistant materials used in the condensing unit may even give those boiler a longer life.

So the debate comes down to how does an inefficient simple boiler stakc up against a modern boiler. If the modern boielr can pay for its extra maintenance costs in saved gas then a condensing unit will certainly do so.

Also to be noted is that a number of the failures of older systems relate to components that would be housed inside the boiler on modern systems. So failures of the pumps, timers, thermostats are clearly no different.

On combis (slightly to the side of the main debate) we have the water flow detectors, (maybe) diverter valve and secondary exchanger against zone and/or diverter valves, cylinder(s) and cylinder thermostats. That's not clear to me which is the less reliable. Sealed Systems v. open header (including all the problems with badly installed open headers). That comes down to the expansion vessel v. the header tank (overflowing, jamming dry, limescale plug at the circuit entry). I'd say it a comfortable points victory for the sealed system, The cost of fixing all the failures is dominated by labour charges.

The gas valves are clearly comparable (a very reliable component in all systems anyway).

So now we are down to the nitty-gritty: Does the fan, APS, PCB & temperature sensors give more trouble and costs that the thermocouple and the extra gas used.

Let's say that for a typical house the difference is £100 year of gas saved (£400 v. £300). I assert that's a realistic test case. A reasonable repair cost for a the modern boiler is around £200 - (half that if you can diy). So if your modern boiler breaks down less than every other year you should be in, you can afford a less reliable modern boiler if you can diy.

I'm have tried to be fair and balanced here. I'm open to correction by reasoned (and preferably numerical) argument.

I'd say that if you buy middle market or above you should save with a modern boiler. Of course if you happen to buy one of the lemons that have been hawked around in the last 10 years you may lose.

HTH

[James]

Do components inside modern boilers generally have to be sourced from the manufacturer - as opposed to being generic as in traditional pumps, timers and thermostats? If so this may increase the cost - and limit availability when the boiler becomes old.

If you are a DIYer who will not work with gas, the scope for correcting problems is more limited when they relate to the boiler rather than external peripherals such as diverter valves and cylinders.

James

[Doctor Evil]

No. it is bad.

..and jublee.

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[Doctor Evil]

Or in some combi's only the water flow detector.

Good post. There is more in a modern boilers case and less outside the case, but overall about the same amount of components. The systems/boilers that are more reliable are the 3-way valveless combi's. Overall they have few components compared to a so-called traditional system, so must be more reliable.

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[Capitol]

Agreed, as IMM would have seen if he had ever taken the back off a washing machine!

Regards Capitol

[Andy Hall]

Mmm.. Trouble is that it's a bit time consuming with a hacksaw.

[Doctor Evil]

My dear mister, washing machines and boilers are very different appliances.

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[Doctor Evil]

It's amazing how the amateurs do things.

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[Dave Plowman (News)]

You've seen inside either?

[Doctor Evil]

....our resdient caberer once again says thing....yes wait for it.....

...his curiosity hold no bounds...I will have to inform him of what it is like inside a boiler...here goes.....Don't look as there are no cabers in there...Don't look!! You will not understand.

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[Ed Sirett]

The pump maybe a special unit or it maybe that the motor part is generic. The timers and thermostats are often external on a modern boiler just like an old one. I choose to use a programmable thermostat rather than the makers integral unit for just this reason.

That's a fair point. Although my argument allowed for professional repairs to the boiler.

[Ed Sirett]

I think you may have missed some of the subtleties of the debate it's not a simple as that. Whilst most of the components can be balanced against each other the crux of the comparison is with the fan/aps/pcb/spark/NTCs etc. v. the thermocouple and liquid expansion thermostat. Clearly the latter is more reliable the debate is balancing the gas saved against the maintenance costs of the former.

I'm arguing that with a reasonable quality modern boiler you _should_ save. The matter is not an open'n'shut case. There are clearly many more components overall in the modern systems but the situation is not as dire as some believe.