Bryant Durapac Plus Series 551a - Manual (Page 14)

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F. 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 potentiome-
ter 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. 16.
G. Dry Bulb Changeover Set Up
Determine the dry bulb changeover set point from Table 6.
The settings are A, B, C and D. Locate the ECON SP potenti-
ometer 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 7.
Table 5 — EconoMi$er Switchover Control Strategy
*Must be selected manually.
Table 6 — Changeover Set Points
*Field-installed accessory.
Table 7 — Default Potentiometer Settings
ECONOMI$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 X X
Differential Enthalpy* X X
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)
2 2 2 2
Differential Enthalpy*
(Btu/lb, Not Adjustable)
1 1 1 1
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 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