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Buderus GB162 Cascade boiler
Buderus has commissioned its largest ever multi-boiler heating system in the UK at Wandsworth Town Hall. The installation features two cascade systems, each comprising 12 Buderus GB162 100kW output boilers.

Cascade heating in the non-domestic sector is becoming increasingly popular and this new Buderus system was designed by Wandsworth Council Design Services working closely with the Buderus technical team and installation contractors T Brown of Surrey.

New state-of-the-art system

The result is a highly efficient heating and hot water system servicing the needs of the 1930s municipal building and the later 7 storey extension council office block.

With the existing boilers having been in use for 20 years, the council took the decision to replace them with a new, state-of-the-art system which would deliver considerable savings in fuel costs, reduce system maintenance, and minimise emission levels.

The Town Hall building incorporates a Registry Office and Civic Suite and is used seven days a week for a wide range of activities and functions.

The heating and hot water system therefore has to be flexible to provide energy efficient operation whilst meeting the varied pattern of usage. In addition the building has a large thermal inertia, so once heated only requires relatively low boiler outputs to maintain the required temperature levels.

Multi-boiler cascade system

Until the recent development and availability of multi-boiler cascade systems, the only previous option would have been for a virtual like-for-like replacement, albeit with more modern appliances.

However the cascade option particularly suited the usage pattern as each 12-boiler cascade can provide heat output which modulates according to the demands of the system down to just 19kW, but has a maximum output of 1,200kW which is more than sufficient to cope with the coldest days and the highest hot water call off.

David Higgins of Wandsworth Design Service says "We opted for a Buderus system for a number of reasons. As well as their expertise in cascade systems, they were able to offer the most complete solution, providing all the necessary components from the single source. This includes pumps, headers, fluing, all gas connections and the complete framework to attach the boilers to, making the whole job very much more straightforward.

Buderus cascade system features

“A particular feature is the frame mounting which raises the boilers to a level where maintenance can be carried out more conveniently and therefore with reduced costs.

“The boiler houses are also much cleaner with less clutter, again easing access for maintenance."

The cascade system uses the compact and lightweight (70kg), GB162 boilers, which are therefore easy to handle even when access is restricted.
The innovative design means it is particularly installation friendly, saving fitting time and costs.

The connection kit is supplied with all the necessary fittings and accessories so the installer only has to build the framework, attach the flow, return and gas pipework and connect the boilers via their individual pump groups.

The cascade system is then ready to be connected to the main heating system. Custom fit insulation is also supplied as part of the cascade kit to ensure heat losses are minimised.

GB162 Cascade system

A four boiler GB162 cascade occupies just 1m2 of floor area and provides 400kW heat output. Each boiler can be automatically controlled to modulate, and therefore to maximise energy efficiency, for the longest possible period, bringing into use extra boilers as and when it is most efficient to do so.

It is important that all boilers are specified and installed correctly to ensure they remain in condensing mode for the optimum time which means return temperatures need to be below 55oC.

Buderus also provide extensive pre and post sales technical consultancy services, including site visits where necessary, to ensure boilers are properly sized and efficiency is maximised.

Award winning heat exchanger

The Buderus GB162 is a versatile boiler designed to meet the rigorous demands of modern commercial space heating. It is whisper quiet in operation and features Buderus' award winning finned aluminium heat exchanger. This has a unique twisted flue channel which brings the maximum amount of water into contact with the hot interior surface of the heat exchanger, optimising heat transfer.

The plasma-polymerised surface of the heat exchanger makes it extremely difficult for particles and dust from combustion to adhere to the surface, effectively making it "self cleaning", maintaining boiler efficiency, improving longevity and reducing the cost of maintenance.

Cost savings

Fuel cost savings have already been noted by Wandsworth Council although accurate assessment figures are not yet available.

Buderus would normally expect a saving compared to the old boilers of at least 20% in cost and operating efficiency and, in addition, the carbon footprint of the building will be much reduced.

The council, contractors and Buderus have carried out a thorough study and investigation into the most efficient operating solution for the specific needs of the Wandsworth Town Hall requirements.

The proof of the success of this solution is already being seen.