14
MECHANICAL COOLING LOCKOUT — Determine the
outdoor-air temperature at which you want the mechanical
cooling (compressors) to be disabled. Locate the mechanical
cooling lockout (MECH CLG LOCKOUT) potentiometer. To
disable this feature, turn the potentiometer counterclockwise
(CCW) to the OFF position. Otherwise, set the value between
10 and 60 F. Mechanical cooling will not operate when the out-
door air temperature is below this value. See Fig. 16.
DRY BULB CHANGEOVER SET UP — Determine the dry
bulb changeover set point from Table 5. The settings are A, B,
C and D. Locate the ECON SP potentiometer and set the dry
bulb changeover set point. See Fig. 16. When the OAT is above
this set point, the damper is limited to minimum position
setting.
If a potentiometer fails, its setting will default to the values
in Table 6.
Table 4 — EconoMi$er Switchover Control Strategy
*Must be selected manually.
Table 5 — Changeover Set Points
*Field-installed accessory.
Table 6 — Default Potentiometer Settings
ECONOMI$ER SWITCHOVER
STRATEGY
SENSORS REQUIRED
Outdoor Air Temperature Outdoor Air Enthalpy Return Air Temperature Return Air Enthalpy
Dry Bulb X
Single Enthalpy X
Differential Temperature XX
Differential Enthalpy* XX
SETTINGS ABCD
Dry Bulb (°F) 73 69 66 63
Single Enthalpy* (Btu/lb) 27 25 24 22
Differential Temperature*
(°F, Not Adjustable)
2222
Differential Enthalpy*
(Btu/lb, Not Adjustable)
1111
POTENTIOMETER DEFAULT SETTING
CO
2
SP (PPM) 1,000
MECH CLG LOCKOUT 50 F
ECON SP D
MIN POS (%) 20
LEGEND
*OAT sensor shipped with economizer option. OAH, RAT, RAH and CO
2
are field-installed accessories.
Fig. 23 — Typical EconoMi$er Sensor Wiring
COM —
Common
DAT —
Discharge Air Thermistor
DM —
Damper Motor
GND —
Ground
OAH —
Outdoor-Air Enthalpy Sensor
OAT —
Outdoor-Air Temperature Sensor
POT —
Potentiometer
RAH —
Return-Air Enthalpy Sensor
RAT —
Return-Air Temperature Sensor
REM —
Remote
