MODES OF OPERA
TION
45%
INCREASED
DEHUMIDIFICATION
MODE
43
7. Increased Dehumidification Ope
rat
ion - Energence Ultra-High Efficiency (3-
to 6-ton)
Energence Ultra-High Efficiency 3 to 6-ton units do not support humidity control as described in Section 6, instead they
use Increased dehumidification for these models.
7.1.
Increased Dehumidification in Wired Thermostat Mode
Increased Dehumidification mode can be activated by the M3 unit controller only when a cooling demand is present. To
remove humidity in the space, the blower runs at 70% of the normal cooling speed until the humidity demand is satisfied.
7.2.
Increased Dehumidification in Room Sensor Mode
When in Increased Dehumidification mode, the unit operates the compressor, indoor blower, and outdoor fan with full
variability to more accurately and efficiently match the humidity load in the space.
Even though Increased dehumidification mode shifts the emphasis of unit operation from cooling to dehumidifying, some
cooling of the air does take place as a side effect of the refrigeration system operating. Because the air is cooled it is
possible to lower the temperature of the space below the space temperature set point while dehumidifying. This is known
as “over-cooling” and is accounted for in the M3 unit controller by having an over-cool limit that is adjustable from 0°F -
6°F, default 2°F.
The range for over-cool limit is also limited by parameter 152, Automatic Changeover Deadband and the heating set
point. Therefore, to set over cool limit to a value higher than two, user should first change parameter 152 to “desired
over-cool limit + 2”. Effective over-cool set point will be >= heating set point + heating deadband + 1.
Set Overcool limit to zero to avoid overcooling.
7.2.1.
Increased Dehumidification without a Cooling Demand
Increased dehumidification mode can be activated by the unit controller without a cooling demand being present. This is
possible when the space humidity is higher than the space humidity set point but the space temperature is equal to or
lower than the space temperature set point. In this scenario the M3 unit controller will operate the refrigeration system
based on the humidity demand; allowing over-cooling of the space based on the over-cool limit set point.
To provide additional humidity removal when no cooling demand is present, the M3 unit controller operates the indoor
blower based on the over-cool limit set point and operates the compressor based on a programmed discharge air
temperature set point designed for optimal moisture removal from the air. In this way, the indoor blower and compressor
work together to achieve a higher latent capacity resulting in lower moisture content in the conditioned space. The M3 unit
controller will cease unit operation in increased dehumidification mode if either the humidity demand in the space is
satisfied or the over-cool limit set point is satisfied, whichever comes first.
7.2.2.
Increased Dehumidification with a Cooling Demand
Increased dehumidification mode can also be activated by the M3
unit controller while a cooling demand is present. This is possible
when the space humidity rises above the space humidity set point
while the unit is already operating due to the space temperature
being higher than the space temperature set point. In this
scenario the M3 unit controller must determine if the cooling
demand or the dehumidification demand is more urgent. Recall
that, during a cooling demand, the unit controller modulates the
blower based off the space temperature set point. Therefore, by
realizing the speed of the indoor blower, the unit controller can
determine the cooling demand of the space and decide if it is more
urgent than the dehumidification demand. From the graph below
one can see that the cooling demand is given precedence by the unit controller when the indoor blower speed is above
90% but the increased dehumidification mode demand is given precedence by the unit controller when the indoor blower
speed is below 85%.
To provide additional humidity removal when increased dehumidification mode is given precedence, the unit controller
operates the indoor blower based on the space temperature set point and operates the compressor based on a
programmed discharge air temperature designed for optimal moisture removal from the air. The unit controller will cease
unit operation in increased dehumidification mode if either the humidity demand in the space is satisfied or the over-cool
limit set point is satisfied, whichever comes first. In the instance where the humidity demand is satisfied but the space
temperature is still above the space temperature set point, the unit controller will transition unit operation back to cooling
mode to satisfy the cooling demand.
