30 May 2005

SPLIT-SYSTEM RESIDENTIAL HEAT PUMP WITH SEPARATE DEHUMIDIFICATION OPERATING MODE


Residential air conditioners and heat pumps operate when the room thermostat senses a temperature
above the control set point temperature. Systems are designed to provide dehumidification simultaneously
with cooling operation and split-system components can be selected to bias performance toward greater
dehumidification. Even so, there are times when the incidental moisture removal capacity of the system
is not sufficient to keep indoor humidity within desired limits. This situation is common during the
spring and autumn, when the sensible cooling load is low and, in humid climates, can occur throughout
the cooling season.
This paper reviews the background and development of a split-type heat pump system with three
operating modes: heating, cooling, and dehumidifying. An analytical method was developed to assess the
effectiveness and operating cost of active dehumidification options. Several technologies were compared
and contrasted using this evaluation tool. A split-system heat pump that flexibly controls both indoor
temperature and humidity was built and tested. Laboratory and field performance results are presented.