—
16
—
F. Mechanical Cooling Lockout
Determine the outdoor-air temperature at which the
mechanical cooling (compressors) will be disabled. Locate the
mechanical cooling lockout (MECH CLG LOCKOUT) poten-
tiometer. 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 outdoor air temperature is below this
value. See Fig. 17.
G. 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 potenti-
ometer and set the dry bulb changeover set point. See
Fig. 17. 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.
H. Ventilation Air (Minimum Position Set Up)
If ventilation air is not required, skip this section. If ventila-
tion air is required, perform the following:
1. The indoor fan must be on to set the ventilation air.
Either put the thermostat in the continuous fan mode
or jumper the R and G terminals at the rooftop unit
connection board.
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 A B C D
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. 24 — Typical EconoMi$er Sensor Wiring
CLG —
Cooling
OAH —
Outdoor-Air Enthalpy Sensor
COM —
Common
OAT —
Outdoor-Air Temperature Sensor
DAT —
Discharge Air Thermistor
POT —
Potentiometer
DM —
Damper Motor
RAH —
Return-Air Enthalpy Sensor
GND —
Ground
RAT —
Return-Air Temperature Sensor
LED —
Light-Emitting Diode
REM —
Remote
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