Talk title: "Replacing a hydro-air boiler with an air-source heat pump"
Bruce Harley is a building performance consultant known for his work on HVAC load calculations, heat pump retrofits, and residential energy efficiency. In this talk from the Westford Symposium, he walks through a real retrofit project replacing a boiler-fed hydro-air heating and cooling system with an air-source heat pump, using it as a case study in the limits and value of load-calculation models. He compares multiple load-calculation methods against the 99% design temperature and measured data, discusses how heat pump capacity drops as outdoor temperature falls, and explains the reasoning behind sizing decisions that avoid oversizing equipment while keeping options open for the future. Along the way he touches on where to find better weather and design-temperature data and closes with a bit of heat pump history.