Field-Monitoring of Whole-Home Dehumidifiers: Initial Results of a Pilot Study

Whole-home dehumidifiers are installed when homeowners want to increase the dehumidifying capability of their air handler without increasing run time. Without a WHD, homeowners must lower the thermostat setting to cause the air conditioner to turn on (or increase the temperature in the case of heating). A mechanical/refrigerative WHD, which comprises a compressor, cooling coils (an evaporator), heating coils, fan, humidistat, and condensate pump, generally is installed in parallel with the air-handling system of the central air conditioner (CAC). Some of the return air from the home is diverted to the dehumidifier. When moist air is drawn into the appliance, it passes over the cooling coils (evaporator), then over a set of heating coils (the condenser) before being returned to the home. The air returned to the home is drier and slightly warmer than when it entered the appliance. The moisture that condenses out of the air drips into a drain line.

Lawrence Berkeley National Laboratory sought to research the energy performance of WHDs. Despite the increase in use of WHDs, however, we found only one published study, in which two WHDs were evaluated in a test laboratory.a We found no publically available field studies of the operation and efficiency of whole-home dehumidifiers. We therefore devised a two-phase project in which Phase 1 serves as a pilot study to understand the range of configurations, operation, and energy use of WHDs. The results of the pilot study, which was performed in a single geographical area, will inform Phase 2, the primary study phase, which will be carried out in multiple geographic regions.

The primary objectives of this project are to (1) expand knowledge of the configurations, energy consumption profiles, consumer patterns of use (e.g. RH settings), and environmental parameters of whole-home dehumidification systems; and (2) develop performance maps of WHD systems. Performance mapping involves observing power consumption, condensate generation, and properties of output air of an installed system under conditions of varying inlet air temperature and relative humidity (RH), as well as different system configurations.

This report focuses on the first of the two objectives; a subsequent report will address performance mapping. This report describes results of the Phase 1 pilot study, which collected detailed data from multiple points in the air-handling systems of WHDs in three study sites in Wisconsin. This pilot field study did not alter flows, disable systems, or modify operation of the WHDs. We selected study sites having different usage patterns and system configurations. We monitored the power consumption—separately for compressor and fan, if possible—and various environmental conditions that were expected to affect the performance and efficiency of the WHDs.