16
DAMPER MODULATION DURING FREE COOLING
Once outside air is suitable for free cooling, the controller modu-
lates the damper based on MAT (mixed air temperature, default)
or OAT (outside air temperature). Refer to Table
10.
If MAT is used when free cooling is enabled, then MAT setpoint
(3MAT SET, configurable in
“Parameter Settings — Advanced”
on page 27) is used for MAT modulating. When MAT falls below
the anti-freeze setpoint (3FRZ PROT), the damper either fully
closes or opens to the minimum position (configurable in
“Param-
eter Settings — Advanced” on page 27.
1. If MAT is lower than MAT setpoint, then the damper is mod-
ulated to maintain MAT setpoint, towards fully closes or
opens to the minimum position based on occupancy status if
MAT continues dropping.
2. If MAT is in the range [MAT setpoint, (MAT setpoint +
neutral zone band (1°F by default))], then the damper position
does not change.
3. If MAT is higher than (MAT setpoint + neutral zone band),
then the damper opens towards fully open.
4. If MAT is 10°F higher than MAT setpoint, then the damper
fully opens to 100%.
If OAT is used when there is a cooling demand, the damper can be
opened to different positions depending on different outside air
temperatures:
1. If outside air is higher than 50°F but lower than the tempera-
ture shutoff setpoint, then the damper is fully open.
2. If outside air is higher than OAT lockout setpoint but lower
than 50°F, then linear modulation is applied when only Cool-
ing Stage 1 input (Y1I) is ON. Result of the following for-
mula indicates the damper’s open position:
((OAT – OAT Lockout Setpoint) / (50 – OAT Lockout
Setpoint)) * (80% – MIN POS) + MIN POS
NOTE: When both free cooling and mechanical cooling are
on, damper remains fully open regardless of the modulating
logic.
LOCATION-BASED SHUTOFF SETPOINTS
The economizer controller can get location-based temperature and
enthalpy shutoff setpoints automatically if it is connected to the
Climatix
™1
mobile application. Once a Wi-Fi/WLAN stick is
plugged in, the economizer controller can establish network con-
nection with the mobile application. The temperature and enthalpy
shutoff setpoints obtained via the phone or tablet’s GPS function
-
ality can then be synchronized to the economizer controller.
COOLING STAGE OPERATION
The economizer controller accepts inputs for 1, 2 and 3-stage
cooling inputs, and reroutes to the RTU through the relay connec
-
tion Y1, Y2 and AUX1/AUX2.
The operation of the cooling stages is determined by the availabil-
ity of Free Cooling provided by the economizer operation mode.
See Cooling Stage I/O Logic Tables
11-12. Based on the use of
Free Cooling, the operating modes are as follows:
• Y1 is Stage 1 Cooling Demand.
• Y2 is Stage 2 Cooling Demand.
• Y3 is Stage 3 Cooling Demand.
• Free Cooling is always the first cooling stage.
• Cooling Stage 1 call from the Commercial Thermostat
(Y1) energizes the Y1 input to the economizer controller.
• Cooling Stage 2 call from the Commercial Thermostat
(Y2) energizes the Y2 input to the economizer controller.
• Cooling Stage 3 call from the Commercial Thermostat ener-
gizes the AUX1/AUX2 input to the economizer controller.
1. Third-party trademarks and logos are the property of their respective
owners.
Table 10 — Free Cooling Functions
CONTROL MODE SENSORS USED ENABLE FREE COOLING?
Control Mode 1
• Fixed Dry bulb
OA (outside air) temperature sensor
and
MA (Mixed Air) temperature sensor
The outside air dry bulb temperature is compared with the set temperature
shutoff setpoint.
If the outside air dry bulb temperature is below the temperature shutoff
setpoint, then the outside air is used to meet all or part of the cooling demand.
Control Mode 2
• Differential Dry bulb
(Dual Dry bulbs)
OA temperature sensor, RA (Return Air)
temperature sensor and MA temperature
sensor
The outside-air dry bulb temperature is compared with the return air dry
bulb temperature.
If both OAT and RAT are higher than the temperature high limitation, then
free cooling is prohibited.
If OAT or RAT is lower than the temperature high limitation, and the outside
air dry bulb temperature is lower than the return air dry-bulb temperature,
then the outside air is used to meet all or part of the cooling demand.
Control Mode 3
• Combination Fixed
Enthalpy and Fixed
Dry bulb Control
OA temperature and humidity sensor, and MA
temperature sensor
The outside air dry bulb temperature and enthalpy are compared with the
set temperature and enthalpy shutoff setpoints.
If the outside air enthalpy is lower than the set enthalpy shutoff setpoint,
and the outside air dry bulb temperature is lower than the temperature
shutoff setpoint, then the outside air can be used for economizing.
Control Mode 4
• Combination of
Differential
Enthalpy and Fixed
Dry bulb
OA temperature and humidity sensor, RA
temperature and humidity sensor,
and MA temperature sensor
The outside air dry bulb temperature and enthalpy are compared with the
temperature shutoff setpoint and return air enthalpy.
If both OA enthalpy and RA enthalpy are higher than the enthalpy high
limitation, then free cooling is prohibited.
If OA enthalpy or RA enthalpy is lower than the enthalpy high limitation,
outside air enthalpy is lower than the return-air enthalpy, and the outside
air dry bulb temperature is lower than the set temperature shutoff setpoint,
then outside air can be used for economizing.
To Next Page
Loading...
