What is a CLV system?

CLV stands for Combination Air Supply-Combustion Gas Discharge. It is a system that combines combustion gas discharge and air supply. A CLV system is ideal for connecting to multiple fan-assisted high-performance boilers (with HR+ or HR TOP energy labels) in blocks of flats. Flue gases are discharged via the inner pipe, and fresh air is supplied through the space between the inner and outer pipes.

Advantages

• Compact: discharge of flue gases and supply of fresh air in a single system.
• Practical: easy to install and maintain.
• Safe: sealed system so harmful gases do not enter living spaces.

Different CLV systems

• Onderdruk-CLV (HR+ of HR TOP)
  A traditional CLV system using negative pressure (flue gases drawn from the appliance), where flue gases in the shared flue gas discharge duct cannot flow back to an appliance that is not in service.
  Usually one brand and type of appliance is used. However, it is no problem to connect central heating boilers made by different manufacturers or different types of boilers.
• Positive pressure CLV system (HR TOP energy label)
  In this type of CLV system, flue gases are removed from the system using positive pressure. A non-return valve in the flue gas discharge pipe ensures that the flue gases do not keep circulating through an appliance that is not in service. Smaller diameters of pipe can be used, which saves space and cost.
  All appliances must be of the same type and made by the same manufacturer to keep the system working properly and maintain the warranty.
• CLV system with outside air intake
  This system is also a CLV system that works with positive pressure. The chimney itself should not be adapted because an insulated stainless steel duct is fitted to the outer wall.
  An outside air intake system can only be used in blocks of flats if the distance between the appliance and the shaft is not too large.

Advice for new-build or renovation projects

For new-build projects, the architect plans the CLV system in the design. For older blocks of flats, it is still possible to use the existing CLV installation by fitting a new shared flue gas discharge duct. This discharge pipe is suitable for condensing heating systems.

We have considerable experience in this field, and we will be pleased to give you advice on the options for your particular needs. We will visit your premises to see whether you should opt for renovation or for the installation of a new system.

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