Page 24
Economizer (Damper) (Continued)
There are six options available to determine outdoor air
suitability (OAS) for free cooling. See table 6. Economizer
settings are shown for each mode in figure 4.
The appropriate sensors are provided when the economizer
is factory-configured. When the economizer is
field-configured, the ODE mode requires additional
field-provided sensor(s). See table 6. The TEMP mode uses
sensors provided with all units.
Table 6. Free Cooling Options
Free cooling mode
DIP SW
positions
MODE
Selection
CONTROL
Selection
OAS Setpoint Calculation
Older M2
Hardware
Newer M2 Hardware
Temperature offset 1,2 to TMP TEMP OFFSET OAT<RAT-OFFSET (0 to 40 F)
Temperature setpoint 1,2 to TMP TEMP OAT STPT OAT<OAT STPT (41 to 70 F)
Remote 1,2 to TMP TEMP ANY OAS sent by network.
Enthalpy differential (Potentiometer set to DIFF) for old
hardware, or ECTO 6.26 = 0 to 75 counts for OFFSET
in new hardware. Old hardware does not use an OFF
SET.
1,2 to ODE ENTH N/A
ODE<IDE (old hardware) or ODE
< IDE OFFSET (new hardware)
Enthalpy setpoint (Potentiometer set to A-D) for old
hardware, or ECTO 6.26 = 130 to 240 counts for new
hardware.
1,2 to ODE ENTH N/A
ODE<POT (old hardware) or
ODE < ECTO 6.26 (new hard
ware)
Global input 1,2 to GLO GLOBAL N/A GLO input
Mode Outdoor air is suitable for free cooling when:
TEMP OFFSET Outdoor air temperature (RT17) is less than return air temperature (RT16) by at least the OFFSET value.
TEMP OAT STPT Outdoor air temperature (RT17) is less than the OAT STPT value.
Remote
Either of the TEMP modes can be used when a network OAS signal is provided by an energy management or building
control system, via BACnet, LonTalk, or L Connection. The network can command OAS, NOT OAS, or AUTO. AUTO
returns to local control of OAS, which is the selected TEMP mode..
ENTH (differential)
Outdoor air enthalpy* (A7) is less than return air enthalpy (A62) by at least the OFFSET value. (There is no OFFSET
value in old hardware.)
ENTH (setpoint)
Outdoor air enthalpy (A7) is less than enthalpy setpoint potentiometer position A, B, C, or D (for old hardware), or less
than ECTO 6.26 STPT value (new hardware).
GLOBAL
Global input is energized by (P297-9). This setting is also used for outdoor air damper applications. Global input also
brings on the blower. (This mode is NOT used when OAS signal is provided via network connection. GLO is only used
when a 24VAC signal is used to energize the P297-9 GLO input.)
Enthalpy includes effects of both temperature and humidity.
To Next Page
Loading...
Need help?
General
