Speaker
Description
In the planning of noise impacts from domestic air source heat pumps (ASHPs), compliance criteria typically refer to a single value in dB(A). Manufacturers provide laboratory test data based on reference thermal conditions, defined flow and return temperatures and single operating points, but in-situ environmental conditions vary widely and continuously, while system characteristics, settings and demands lead to wide variations in operational patterns. To demonstrate compliance with design criteria, a protocol for the measurement and assessment of in-situ sound emissions is required. A framework based on the highest daily LAeq,1hr sound emission is proposed; regression against the daily minimum temperature enables the emission to be expressed at 7°C, the laboratory reference condition. Spatial, temporal and environmental contamination factors are discussed. Pilot measurements at eight installations, comprising more than 1,200 hours of monitoring, illustrate three distinct operational sound emission profiles – unimodal, bimodal and continuously variable – and the potential to use a short-term measurement of a hot water cycle to infer longer-term emission is explored. Two dimensions along which in-situ operation may diverge from the part-load laboratory test condition are discussed qualitatively. A complementary qualitative protocol, based on narrative interviews, is described for use where the effect of an installation on residents is in question.