Co2 Mode; Doas Mode - Danfoss MCX-RTU User Manual

User Guide | MCX-RTU Rooftop
© Danfoss | ADAP-KOOL® | 2018.11
on. For Variable Speed Fan, the fan will run at Cooling Max Fan Speed until all stages of dehumi-
dification are running at 100% capacity for the time specified in the Max Capacity Period setting.
Once this occurs, the fan modulates trying to lower the compressor capacity to 98%. If the fan
is configured for continuous operation the fan modulates to the Cool Min Fan Speed with no
demand for dehumidification. If the fan is configured for On Demand, and there is no demand
for dehumidification, the fan will either modulate to Cool Min Fan Speed or turn OFF depending
on the setting of the Fan Control Demand parameter.

CO2 Mode

The CO2 Mode is for health and safety of everyone in the facility. CO2 Mode has priority over all
other modes. And there are no lockouts to effect operation.
CO2 control requires an Analog Output to control the damper. The damper activates when the
Zone CO2 level reaches CO2 Target minus the CO2 Range. The damper modulates proportionally
between the CO2 Target minus the CO2 Range and CO2 Target plus the CO2 Range.

DOAS Mode

DOAS Mode is a combination of all the above modes.
DOAS Mode is controlled by the value for C23 under Setup Options. If set to yes, then the opera-
tion is as follows.
Fan Speed is fixed to the value set by parameter FN7 – OvrdFanSpeed(Parameters->Fan)
Outdoor Temperature and Outdoor Relative Humidity are used in place of both the Zone Tempe-
rature and Zone Relative Humidity for the Cooling/Heading/Dehumidification modes.
The Damper is set to the DM0(Damper Ovrd Value) value and does not modulate. This value will
typically be set to 80%. Note that if this value is less than 100%, and CO2 Mode is calling for the
Damper to open more, then the Damper will open to the value requested by the CO2 mode.
RS8KE102 | 11