Combination boilers for larger properties

Martyn Bridges from Worcester, Bosch Group, takes a closer look at the NHBC's current regulations relating to the installation of combination boilers for larger properties.

Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group.

"In September 2006, the NHBC published new standards for the building industry, which included a section dedicated to 'Hot Water Services' (section 8.1, sub-paragraph D9) and in particular, the suitability of combination boilers for larger properties.

"It was with interest and a degree of annoyance that I first read the document back in September, as the main recommendation made in section 8.1 focusing on hot water provision was that combi boilers are only deemed suitable by the NHBC for supplying one outlet at a time and therefore should not be specified for homes with more than one bath or shower.

"Just recently, the NHBC has further clarified its requirements for a single bedroom property, which is for a combi boiler that delivers 15 litres per minute.

This puts things in perspective to a certain degree, as according to the NHBC, even a one bathroom bedsit should be fitted with a 37kW combi boiler to supply adequate hot water.

"Whilst there has been plenty of debate about the suitability of combis to cope with the demands of larger households over the years, it is generally understood throughout the trade that combis can cope admirably with the greater demands of larger properties, as long as a boiler with a large enough output is specified for site conditions in the first place.

"In fact, contrary to the NHBC's suggestions, we know there are hundreds of thousands of combination boilers installed in properties with more than one shower and bath that are adequately meeting the hot water requirements of those living in them.

"Knowing what we know, it is disappointing to see the NHBC creating a barrier to the installation of combi boilers in the face of the facts, which suggest suitability for a wide range of installations.

"Since combination boilers were first pioneered in the UK in the late 1960's by Worcester's founder, Cecil Duckworth, their popularity has increased quite significantly.

The advent of condensing technology in the early nineties also made it possible to significantly improve boiler efficiency to deliver levels of over 90% average seasonal efficiency on SEDBUK 'A' rated models.

"Today, combi boiler sales account for over 70% of all new domestic boilers installed in Britain each year.

As well as being an ingenious space saving idea, eliminating the need for a hot water storage tank, it's quite clear that having hot water on demand is an attractive proposition for many homeowners living in a variety of property types -- from apartments to family homes.

"As with all heating and plumbing installations, the key to best performance when installing a combination boiler (condensing or non-condensing) is in specifying the correct boiler size to suit the site requirements in the first place.

"In my experience, customer dissatisfaction relating to combi performance can often be quite quickly traced back to a boiler not being correctly sized for household requirements to begin with.

This is especially true if the complainant happens to live in a four bed house and a smaller combi, more appropriate to an apartment, has been installed.

With this in mind, it is perhaps easier to understand the NHBC's stance however, the over cautious approach to blocking combi boiler installations is not to the way to be heading in my opinion.

"More training, education and guidance about the suitability of combis would be far better to instill confidence and help get it right.

At Worcester, we place a great deal of emphasis on installer training in order to support the trade when it comes to selecting the right boiler size and type for the job.

We also have a wide variety of combination boiler options to ensure there is a product to suit most situations and in particular, the demands of larger households.

"Since the NHBC introduced its new guidelines last year, we have been in regular contact with the Head of Standards and other senior members of the Technical Standards Committee to try to encourage them to re-think their position on the suitability of combination boilers for new homes with more than one bath or shower.

"To date, we have been unsuccessful in our attempts to secure a revision of the current standards and the NHBC is not planning to amend its technical handbook at present.

However, if the guidelines remain the same, the NHBC is effectively ruling out the installation of many of the wall hung combis, like the Greenstar 37CDi and 42CDi boilers that are produced by Worcester, and those offered by other manufacturers.

"In adherence with the guidelines only the Worcester Highflow 440 or oil-fired Heatslave is deemed suitable from our entire range for installation in properties with more than one bath or shower.

This is totally inaccurate when we know that significant volumes of combi boilers are working more than successfully in such instances.

For this reason, we will continue to campaign for changes to the standards and hope to see more positive developments in the months ahead.".

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