Dear All Happy Xmas for the coming season (04 that is)
I have a Glow Worm Fuel Saver MkII balanced flue boiler that has been in my
4 bed detached house since it was built 15 years ago. I have often had problems with the pilot light going out and it is not the easiest to relight especially for my wife. Apart from the pilot light the boiler has been very reliable. Would someone be kind enough to advice me on whether I should consider a replacement?
How much more efficient are the modern boilers and if replaced any guess on the % yearly saving over this boiler. What make and model should I be looking at how much should I expect to pay for the boiler and the skill of a tradesman to change.
IMHO if it keeps going then leave it. The old boilers need virtually no attention and last for 'ever'. I had a 30 year old boiler that worked fine if a little inefficiently. When we had the kitchen redesigned I replaced it with a combi, much more efficient, it saved me about £6 per month on gas. However, at £800 for the new boiler with installation, assuming it never goes wrong, it's going to take an awfully long time to recover the money and because there are so many more parts in it it's bound to go wrong more than the old one did making the payback time even longer.
I've been there and have the T-shirt, Peter, with the self-same boiler. Mine was installed when the house was built in 1985 and replaced last year.
The pilot light going out issue happened on mine and is generally either because the thermocouple is failing or because the pilot light jet is dirty or perhaps set too low. The thermocouple is a metal capsule in the pilot flame, together with a capillary tube which then goes out of the combustion compartment and to a connector at the gas valve. Replacing it is very easy and cheap (they are generic parts at about £3 from a plumber's merchant.).
If it isn't that, then it would likely be the pilot jet adjustment or cleaning, or there is a possibility of the gas valve having a problem. One of these would cost typically in the £50-70 area for the part.
On mine, the thermocouple failed, and then the thermostat, and it was at that point that I started to consider a replacement rather than throwing good money away on something at the end of its useful life. To be honest, the manuafacturing quality of these boilers was not great to begin with - every time I took the covers off for a repair, I would cut myself on the sharp metal pieces inside.
Boiler efficiencies have improved enormously since this model. There is a UK testing method and database of boilers at
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The principle behind this is a testing method which looks at the UK climate and factors the seasonal variations into boiler efficiency calculations and measurements, rather than just taking the raw efficiency figures of energy in and energy out. There is also a Europe wide measuring system under discussion, but the SEDBUK information is a useful guide for the moment. They do point out that you should not use the last fraction of a percent to select a boiler.
From this, if you look up the Glow Worm Fuelsaver, you will find that it has a SEDBUK efficiency of 65%. New boilers being installed today, are required under the Building Regulations to have a SEDBUK efficiency of at least 78%. From a technology perspective, updated versions of conventional boilers just about manage to scrape into this limit, and you would see Mk3 and 'e' versions to do this. Manufacturers used various means to be able to continue selling them.
If you want to, there is nothing to stop you buying a replacement boiler at this efficiency level if you choose. However, you can do a great deal better using a condensing boiler. These work by having a larger and more efficient heat exchanger and by arranging to condense steam from the combustion process to water or water vapour. The principle here is of the latent heat of condensation, whereby heat energy is released when a gas condenses to its liquid phase. It's the opposite of evaporation - think about sweating making you cool.
The effect is that you can achieve an efficiency, as measured by the SEDBUK methods of 90-91%. Compared with 65%, this is a huge saving. I have had a condensing model for just over a year and am seeing
25-30% savings on gas consumption - pretty much the predicted figures. It's worth noting that current government thinking is to raise the bar on efficiency ratings to 86% next year. Effectively this will take all of the older technology products off the market anyway.
For the most part, current and new generation condensing boilers are of good quality. Early generation UK manufactured ones gained a poor reputation simply because they were poorly designed and used the wrong materials. One of the aspects of condensing boilers is that the condensate produced is slightly acidic and that has to be accounted for in the materials used. Generally in modern products it is. The condensate is fed from the boiler via a plastic pipe to a convenient drain. Condensing boilers have been in use in Holland and Germany for at least 15 years, and so the early issues were resolved a long time ago.
In terms of cost, you will pay approximately £200 more for an equivalent model condensing boiler, or as little as £100 between a not quite bottom of the range conventional boiler and a reasonable condensing model.
People here have seen good results with products from Keston and Vaillant and these come in at the £700-900 range.
It's difficult to put a figure on the labour involved because it will tend to vary by what is involved. Some boilers will operate on an open vented environment such as you have today, others require the system to be sealed, yet others do either. Changing the system over is not a major issue in most cases.
Another useful upgrade while you are doing this would be to improve the hot water system by replacing the cylinder with a fast recovery type.
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