Sequence of Operation
compressor will run until the desired setpoint
temperature on the thermostat is achieved.
Once the thermostat is satisfied, the compressor
shuts down and the fan ramps down in either fan
only mode or turns off over a span of 30 seconds.
Auxiliary electric heating coils are not available on
the EP product line.
Figure #7 – Modulatng
hot gas reheat with
HOT GAS REHEAT (HGR)
Hot gas reheat allows the user to not only control
space temperature, but also humidity levels within
the conditioned space. An excess of moisture in the
space can allow mold growth leading to damage in
the structure or interior surfaces as well as
reducing the air quality and creating an unhealthy
The typical control of a unit is by a thermostat that
senses the temperature in the space. By utilizing a
humidistat in addition to the thermostat we are
able to monitor the humidity levels in the space as
well. The HGR option allows cooling and
dehumidification to satisfy both the thermostat and
Hot Gas Line
Subject to change without prior notice
Once the thermostat reaches set point temperature
and the humidity is above set point, the unit will
operate in the hot gas reheat mode first by cooling
and dehumidifying, then reheating the air using hot
refrigerant gas before delivering it to the space
usually 2°F to 5°F below room temperature. The
unit is operating as a dehumidifier. By reheating the
air along a constant sensible heat line the relative
humidity of the supply air is reduced.
The moisture removal capacity of a specific heat
pump is determined by the unit latent capacity rating.
A heat pump's latent capacity can be determined by
reviewing the heat pump specification data sheets.
Depending upon the entering water and air
conditions a total and sensible capacity can be
interpolated from the data sheets. Subtracting
sensible capacity from total capacity yields latent
capacity. Dividing the latent capacity by 1069 (BTU/
LB of water vapor at 80° DB and 67° WB) yields the
amount of moisture removal in pounds per hour.