Bryant 548J User Manual
Page 51
51
0
5
10
15
20
25
30
0.13 0.20 0.22 0.25 0.30 0.35 0.40 0.45 0.50
STATIC PRESSURE (in. wg)
FLOW
IN
CUBIC
FEET
PER
MINUTE
(cfm)
C06031
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
sensor
(part
number
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
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
R
and SR+ on the EconoMi$er IV
controller (see Fig. 68).
In this mode of operation, the outdoor-air temperature is
compared to the return-air temperature and the lower
temperature airstream is used for cooling. When using this
mode of changeover control, turn the enthalpy setpoint
potentiometer fully clockwise to the D setting. (See
Fig. 72.)
ECONOMI$ERIV
ECONOMI$ERIV
CONTROLLER
GROMMET
RETURN AIR
SENSOR
RETURN DUCT
(FIELD-PROVIDED)
C07085
Fig. 75 -- Return Air Temperature or Enthalpy Sensor
Mounting Location
CONTROL
CURVE
A
B
C
D
CONTROL POINT
APPROX.
deg. F (deg. C)
AT 50% RH
73 (23)
70 (21)
67 (19)
63 (17)
12
1
4
1
6
18
20
2
2
24
26
28
30
32
3
4
36
38
40
42
44
46
90
10
0
80
70
60
50
40
30
20
10
ENTHALPY BTU PER POUND DRY AIR
85
(29)
90
(32)
95
(35)
100
(38)
105
(41)
110
(43)
35
(2)
35
(2)
40
(4)
40
(4)
105
(41)
110
(43)
45
(7)
45
(7)
50
(10)
50
(10)
55
(13)
55
(13)
60
(16)
60
(16)
65
(18)
65
(18)
70
(21)
70
(21)
75
(24)
75
(24)
80
(27)
80
(27)
85
(29)
90
(32)
95
(35)
100
(38)
A
A
B
B
C
C
D
D
RELATIVE HUMIDITY (%)
HIGH LIMIT
CURVE
APPROXIMATE DRY BULB TEMPERATURE--degrees F (degrees C)
C06037
Fig. 76 -- Enthalpy Changeover Setpoints
548J