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Controlling efficiency

Buderus 4000 series controller
Installers new to the commercial heating sector occasionally have concerns about the complexity of controls technology, but modular option, full text displays and pre-configured programmes for systems are now commonplace.

Building regulations


Under present Building Regs, specific energy efficiency criteria for heating in non-domestic buildings are applicable to both new build (Part L2A) and existing buildings (Part L2B).

These regulations set minimum acceptable performances for heating and hot water services and lay down minimal operation seasonal boiler efficiency levels which are based on average boiler efficiencies operating at 30% and 100% output, with all boilers having to achieve a minimum 84% level.

There are also minimum control packages required, dependent upon boiler output. All new installations must incorporate zone-specific timing and temperature controls for buildings with floor areas over 150m2.

Weather compensation


Weather compensation is also required unless a constant temperature supply is needed. Installations between 100 and 500kW are also required to have optimal start/stop control with night set back or frost protection, two-stage firing or multiple boilers, measures to limit heat loss from non-firing modules, and sequence control for multiple boilers.

Boilers over 500kW must also have fully modulating burner controls.
Slightly different rules come into play for existing buildings - natural gas boilers must achieve minimum 80% efficiency, zone control where the building floor area is greater than 150m2, room thermostats which control through a diverter valve, and time clock controls as a minimum.

Heating Efficiency Credits


However, the overall performance of the system must achieve the 84% level and this is made possible by gaining Heating Efficiency Credits which are awarded for additional controls or functions added to the basic specification e.g:

  • 4 = Full building management system.
  • 2= Optimised stop/start, direct acting weather compensation or boilers oversized by no more than 20%.
  • 1.5 = Optimised start or weather compensation with mixing valve.
  • 1 = Sequential control of multiple boilers, monitoring and targeting, thermostatic radiator valves, full zoned time control, decentralised heating systems or multiple boilers.
  • 0.5 = Room thermostat or sensor controlling boiler water temperature in relation to heat load and optimised stop.

Controls and energy efficiency


Using Buderus controls has the potential to achieve up to four points with a single boiler system and up to five points with a cascade system. for example, with our 4000 controls this can be achieved with a combination of direct acting weather compensation (2 points) , full zoned time control of individual circuits (1 point) and if BFU room control is used for each circuit (1 point) the additional point can be achieved on cascade systems for the sequential control of multiple boiler systems.

Controls are the key to improved boiler efficiency and there is no need to limit the installation to the 84% minimum. In fact, Buderus commercial boilers all exceed the 84% minimum rating in their own right so adding extra control options will ensure that the installation performs over and above the minimum requirements in terms of energy efficiency.