Rethinking Heat Transfer: Why 'Natural' Isn't Always Ideal for Air-to-Water Systems
As air-to-water heat pumps replace boilers in North American hydronic systems, designers must rethink traditional approaches to heat transfer, or risk costly and inefficient installations.
Air-to-water heat pumps are becoming increasingly common as primary heat sources in North American hydronic systems. This transition is likely to continue. As it does, some practitioners are learning - sometimes painfully - that heat pumps are not boilers.
When boilers were paired with poorly matched balance-of-system design, it was common for installers to keep turning up the water temperature to compensate for poor heat transfer elsewhere in the system. In some cases, the higher water temperatures eventually “overpowered” the heat transfer bottlenecks, albeit at reduced efficiency, and at exhaust gas temperatures that PVC pipe was never meant to handle.
