Evaluation of and Algorithm Development for the IAPMO Test Protocol for Horizontal Drain Water Heat Recovery Devices

This project created algorithms predicting the performance of drain water heat recovery devices as a function of their installed angle. The algorithms use the same process as previous Pacific Gas and Electric (PG&E) drain water heat recovery projects1. Four representative DWHR devices, two horizontal and two vertical, were installed at the PG&E Applied Technology Services (ATS) laboratory. Tests identified the steady state effectiveness of these devices at different installation angles. Based on recommendations from device manufacturers, the horizontal devices were tested at a range from 3 to 30 degrees from horizontal, and the vertical units were tested at a range from 70 to 87 degrees from horizontal. Tests on horizontal devices started at 3 degrees, not fully horizontal, because plumbing codes typically stipulate a minimum slope of ~3 degrees to ensure proper drainage.