Pipe sizing based on domestic hot water consumption in Norwegian hotels, nursing homes, and apartment buildings

Abstract

Sizing of domestic hot water pipes are to a large extent based on calculations of peak flow rate according to current guidelines. This article compares detailed field measurements of peak flow rates in Norwegian hotels, nursing homes and apartment buildings with calculated values according to Norwegian NS 3055, German DIN 1988-300 and European EN 806-3 code of practice. Results indicate that existing guidelines overestimate the peak flow rate by a factor of 1.2– 2.6, depending on type of building and which standard the calculations are based on. In most cases, this also resulted in oversizing the pipes. Calculations according to NS 3055 are closest to the field measurements, on average overestimating the peak flow rate by a factor of 1.6. To analyze the effect of different measurement intervals, the measured peak flow rate is also calculated as a moving average for different time steps (t). Compared to using an interval of 2 s, averaging the data over 10 s would underestimate the peak flow rate by a factor of 0.80– 1.0. Using a 30 s interval would underestimate the peak flow rate by 0.67– 0.94.