Bryant 548J Service And Maintenance Instructions page 51

30
25
20
15
10
5
0
0.13 0.20 0.22 0.25
STATIC PRESSURE (in. wg)
Fig. 74 - - Outdoor- - Air Damper Leakage
Differential Dry Bulb Control
For differential dry bulb control the standard outdoor dry
bulb sensor is used in conjunction with an additional
accessory dry bulb
CRTEMPSN002A00). The accessory sensor must be
mounted in the return airstream. (See Fig. 75.) Wiring is
provided in the EconoMi$er IV wiring harness.
Outdoor Enthalpy Changeover
For enthalpy control, accessory enthalpy sensor (part
number HH57AC078) is required. Replace the standard
outdoor dry bulb temperature sensor with the accessory
enthalpy sensor in the same mounting location. (See
Fig. 66.) When the outdoor air enthalpy rises above the
outdoor enthalpy changeover setpoint, the outdoor-air
damper moves to its minimum position. The outdoor
enthalpy changeover setpoint is set with the outdoor
enthalpy setpoint potentiometer on the EconoMi$er IV
0.30 0.35 0.40 0.45 0.50
C06031
sensor (part number
CONTROL
CONTROL POINT
CURVE
APPROX. deg. F (deg. C)
AT 50% RH
A 73 (23)
B
70 (21)
C 67 (19)
D 63 (17)
(18)
60
(16)
A
55
(13)
B
50
C
(10)
D
45
(7)
40
(4)
35
(2)
35 40 45 50 55 60
(2) (4) (7) (10) (13) (16)
APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)
Fig. 76 - - Enthalpy Changeover Setpoints
controller. The setpoints are A, B, C, and D. (See Fig. 76.)
The factory-installed 620-ohm jumper must be in place
across terminals S
controller (see Fig. 68).
In this mode of operation, the outdoor-air temperature is
compared to the return-air temperature and the lower
temperature airstream is used for cooling. When using this
mode of changeover control, turn the enthalpy setpoint
potentiometer fully clockwise to the D setting. (See
Fig. 72.)
ECONOMI$ERIV
Fig. 75 - - Return Air Temperature or Enthalpy Sensor
85 90 95 100 105
(29) (32) (35) (38) (41)
80
(27)
75
(24)
70
(21)
65
A
B
C
D
65 70 75 80 85 90 95 100 105
(18) (21) (24) (27) (29) (32) (35) (38) (41)
51
and SR+ on the EconoMi$er IV
R
ECONOMI$ERIV
CONTROLLER
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
Mounting Location
110
(43)
HIGH LIMIT
CURVE
110
(43)
GROMMET
C07085
C06037