Measuring the performance of a water heat recovery system

Gray water heat recovery systems can instantly capture energy from household wastewater, thereby improving the thermal balance of buildings. To measure the actual performance of these systems, the CSTB has been offering tests in its Cofrac-accredited laboratory since September 16, 2014.

The CSTB Recado laboratory in Nantes conducts tests that measure the performance of systems that instantly recover heat from gray water. Cofrac recognition of these tests is the culmination of work conducted over several years with industry partners to characterize the systems as the basis for developing testing methods to measure system efficiency.

There are three options for using the heat recovered from gray water by units located at the earliest-possible position in a drain: return the heated water to the domestic hot water tank, return it to the cold water inlet of the shower mixing valve, or return it to a hybrid system that feeds both the tank and mixing valve.

The CSTB test characterizes all three of these options. Manufacturers must then request Title V approval from the DHUP (French Department for Housing, Urban planning and Landscape), which recognizes this test, in order to promote their systems as compliant with 2012 Thermal Regulations. Title V makes it possible to include the performance of innovative processes in the calculation methods for predicting the thermal balance of buildings. Gray water heat recovery systems are also covered by the Technical Approval Procedure, the stage that precedes certification of these processes.