combi & condensing boilers

Perhaps some 90% of the country’s homes have conventional central heating - boiler heating radiators and a water tank (cylinder). Not only is this very boring it’s also far from ideal. Radiator heating is a rather feeble (if quick) way of heating a home. Radiators are usually made of steel. However, it is possible to get more modern-looking aluminium radiators as well as a plethora of modern sculpture-looking heat emitters. There is even a metal ‘tree’ available which is simply aluminium tubes with hot water running through them.

At least these look better than a slab of painted metal on your wall. So-called ‘hospital’ radiators continue to be popular too. I am continually shocked to see that the market for reclaimed iron radiators continues apace as well. These are dust traps, and poor heat emitters compared to modern radiators. Neither will you be able to paint them like you would an ordinary radiator. Still, if you can afford the reclaim prices than you can afford to have them professionally sprayed in any colour you like!

In the USA there is a sizeable market for small radiators to be covered up with a cover that incorporates a fan. A sensor switches the fan on when it senses the heat delivered to the radiator. This is quite desirable as it means a small box as a ‘radiator’ (though really it’s become a convector, which is not the same thing) - though it should be noted that the fans have to be cleaned annually. Some noise is also inevitable, making it less suitable for light sleepers.

The past twenty years have seen the rise of the ‘combi’ (combination) boiler. As the name suggests this combines heating and water heating in one appliance. There’s no need of a hot water cylinder. Combi boilers have now taken over 50% of the new boiler market. This has been a quite amazing success. The advantages are obvious, such as no cylinder, no extra piping, no tanks in the loft to freeze or crack. They have been the darling of property landlords and plumbers alike. There are many small heating companies currently installing a complete central heating system in one day - thanks to combis!

However, combis haven’t come without their own problems. In hard water areas, like the south east, the main problem has been limescale build-up within the hot water heat exchanger. This is because the combi heats water on demand. It’s like a kettle continually heating water. Conventional hot water cylinders scale-up too. But it is many years before the effects are felt, and by then it’s usually ready for replacement anyway.

The vast majority of limescale inhibitors available to protect the boiler simply don’t work. There are two fairly well-known ones on the market that clog themselves up with their dosing contents just a couple months after fitting! However, limescale is not the only problem with combi boilers. By their very design they are complicated. Most have two heat exchangers, a fan, a pump, a diverting valve, a flow switch, an electric gas valve, electronic ignition, and of course a burner. However, there are numerous sensors, switches, and always at least one printed circuit board. This is a recipe for unreliability. Some combis also have an extra water tank fitted to the side to provide a pre-heated bank of water.

From April 1st 2005 most boilers have had to be ‘condensing’ as well. A condensing boiler uses a heat exchanger to capture heat from the ’fumes’ that go out of the flue. It makes boilers more efficient to fuel and is therefore beloved by the Greens - though no account has been taken of the resources used to make these changes! A typical heating system could see an annual saving of £160, with a maximum saving of 40% a year. These are impressive figures, though treated with some caution by veteran economists with a calculator!

I believe this is another example of the silliness that surrounds ‘going green’. Even if you believe that our CO2 is affecting the climate to a huge degree then this exercise is still futile. It has been worked out that any possible reduction in emissions is quite literally akin to a glass of water in an olympic-sized swimming pool. And that would be under ideal transference conditions way into the future.

Condensing boilers are more expensive (of course!) and it will take an average user over 11 years to retrieve the outlay. And let’s not forget that even more technology has been built in, so they are likely to be even less reliable than previous conventional boilers. If it requires more call-outs then considerable amounts of energy will be used by the very practice - you’ll use energy to contact your engineer, he will travel some distance by diesel van to get to you, the part will have had to be manufactured - and so on. The figures simply don’t add up. A colleague of mine recently removed a totally-finished condensing boiler that had been installed just seven years ago. This then means a considerable financial loss to the user and an impact on the environment!