Do you know anyone with a condensing boiler, have you seen a condensing boiler in operation? Condensing boilers are installed in many homes but are not that well known and are often seen as part of the boiler installers technical mumbo-jumbo.

Dispelling the mystery we can see that a condensing boiler is a high efficiency advanced boiler that incorporates an additional heat exchanger in order that the red-hot flue gases transfer a percentage of their contained energy to pre warm the water in the boiler system. Once working at high efficiency, the water gases developed in the burning action condense back into a liquid putting out the latent heat of vaporisation and transferring their heat into the heat exchanger.

As part of the normal operation of the boiler it will regularly be producing a small amount of liquid water, condensed from the water vapour referred to earlier. This needs to be removed from the boiler and is allowed to flow to the outside through a simple water pipe. There are no complex installation requirements for this other than that it can drain away without causing nuisance. An experienced boiler installer will also ensure that the positioning of the drainpipe is such that it will not freeze in winter or block with autumn leaves as-of these problems can lead to the boiler shutting down causing a central heating problem.

The boiler is recommended to be mounted on a wall and the output gases will travel through the flue. The boiler manufacturer will have recommendations on the length of travel of the flue pipe and the angle at which it ought to be positioned. Initial hot water requirements are served by a small-scale storage tank to facilitate speedy hot water accessibility.

What size of boiler should I purchase?

To achieve maximum boiler efficiency, in line with the theoretical design, you need an energy audit conducted in order to ascertain the right size of boiler and power output for your home. In earlier years boiler installers filled larger boilers than were called for. Although this meant that there was little probability of the boiler falling short on its requirements, regardless of the wintertime weather, it also meant that they were only using a piece of their heat generation capabilities, and so functioning in an inefficient way. If you have bettered the energy efficiency of your property since the previous boiler was installed, you will probably find that you will need a smaller boiler than the current one.

We recommend looking for professional advice from a CORGI registered installer before selecting a suitable replacement boiler.

Do the radiators need to be outsized with a condensing boiler?

The fundamental reason for this improved efficiency from a condensing boiler is that it has an oversized heat exchanger. More Prominent radiators would result in cooler return water temperatures, and so enable greater energy efficiency, but the further saving is not shown to be cost effective, keeping in mind that the system is is only using a small part of its total capacity for the greater part of the wintertime. That in all likelihood remains true, though the reduced heating demand for new build may easily mean that homeowners would now allow over-sized radiators more willingly.

The SEDBUK initiative assessed these subjects, and evaluated whether there needed to be new considerations for condensing boilers when compared with traditional boilers. The result was that no new recommendations were necessitated, and the test results for the condensing and the existing boilers use the same SEDBUK calculation.

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