PROVIDING cost-effective space heating and hot water is a key part of building services design. Originally, one boiler was used to provide both heating and dhw functions - probably quite inefficiently.
With the introduction of direct fired water heaters in the 1970s, decentralised hot water production increased energy efficiency and signalled lower running costs for end users. However, the new generation of commercial boilers is already reversing the trend back towards using just one appliance for up to three different heating functions.

Boiler manufacturer Vokera is one of the first to introduce a boiler which is capable of running three different temperature circuits from one unit. The new high efficiency CondexaPRO can provide space heating, underfloor heating and domestic hot water, and marks Vokera's first venture into the light commercial heating market.

Peter Crutchley is Vokera's commercial business unit director, and says that with the introduction of Part L2 for commercial heating installations, the use of high efficiency products with accurate control systems has become even more important.

'The new generation of commercial boilers will be modulating rather than two stage or on/off. This will reduce burner cycling and result in a more precise matching of burner/boiler load, representing significant energy savings for end users, as well as reduced carbon emissions.'

The secret of the CondexaPRO system is down to high-tech controls, meaning it simultaneously controls three different circuits, each operating at different temperatures. A three-temperature circuit means CondexaPRO units are ideal for domestic hot water, high temperature (heating) and low temperature (under floor heating). The three water systems can be channelled directly or via a header system utilising operating controls as required. This high control system means that heat is only supplied when required, which makes the installation extremely energy efficient and ultimately saves money for the end user.

'It's no longer just about providing a high efficiency boiler but engineering that product to be totally flexible,' says Peter. 'In addition to high turn-down ratios, controls are playing an even bigger part to ensure boilers remain in high efficiency mode across varying heat demands.'

Pre-packaged boilers are gradually changing the light commercial end of the heating market. Where previously a boiler/burner package would be specified, compact wall hung boilers like CondexaPRO can be more cost effective. Available in two sizes (50kW and 100kW) the boilers can be installed in a modular configuration enabling an output from 13kW to 353kW at a flow/return temperature of 80/600C. The fully modulating burner means efficiency levels are maintained, with 108.7% nett at (30%) part load.

Because the CondexaPRO is so flexible, it can be used for both new build and refurbishment, in commercial and public buildings, as well as multi-occupancy or large private homes. In fact one of the first installations was for a private home in Scotland, where one boiler provides underfloor heating for the ground floor, water for radiators on the first floor as well as domestic hot water throughout the home.

For modular applications, both the 50kW and 100kW versions are available as master units, using 100kW slave models. All utilise the same size casing, with the 50M housing a single heat engine, and the 100M/100S models incorporating two heat engines. The boilers are designed for a maximum hot working pressure of 6bar, with a minimum pressure of 0.5bar. They are only suitable for sealed/pressurised systems. A LPG conversion kit and an outside temperature sensor are supplied as standard with each master boiler.

Where larger outputs are required, a simple master/slave PCB arrangement allows the master unit to control up to 60 heat engines (potentially 2.65MW), and gives the system designer a high degree of flexibility. Each 50M/100M incorporates a master and slave PBC for each heat engine using a serial bus connector that can be utilised to connect additional slave units (100S). In turn, each slave unit incorporates 2 slave PCBs (one for each heat engine) and this allows easy and simple site set up.

It's the master PCB which controls up to three different heating circuits and their required temperatures independently. This affords a great degree of flexibility where a DHW cylinder, underfloor heating and a heating circuit require differing temperatures simultaneously and also allows prioritising of the circuits.

Another big advantage with the modular application is the ability to sequence each individual heat engine. This ensures that the output is matched as accurately as possible to demand, further increasing the fuel efficiency. An additional option can be enabled whereby certain boilers switch off once the modulation phase has been reached, and/or having routine alternation of the boiler firing sequence.

For all energy users low carbon emissions are key, and the CondexaPRO has a European Class 5 classification for Nox emissions, at less than 20ppm.

In the drive for lower carbon emissions, and higher efficiency, a return to centralised plant deserves another look.


Volkera T: 0870 333 0220