Bryant 551B Installation Instructions Manual page 27

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. 21.) When the outdoor air enthalpy
rises above the outdoor enthalpy changeover set point, the
outdoor-air damper moves to its minimum position. The outdoor
enthalpy changeover set point is set with the outdoor enthalpy set
point potentiometer on the EconoMi$er IV controller. The set
points are A, B, C, and D. (See Fig. 36.) The factory-installed
620-ohm jumper must be in place across terminals SR and SR+
on the EconoMi$er IV controller. (See Fig. 21 and 37.)
Differential Enthalphy Control
For differential enthalpy control, the EconoMi$er IV controller
uses two enthalpy
CRENTDIF004A00), one in the outside air and one in the return
air duct. The EconoMi$er IV controller compares the outdoor air
enthalpy to the return air enthalpy to determine EconoMi$er IV
use. The controller selects the lower enthalpy air (return or
outdoor) for cooling. For example, when the outdoor air has a
lower enthalpy than the return air, the EconoMi$er IV opens to
bring in outdoor air for free cooling.
2500
2000
1500
1000
500
0
0.05
STATIC PRESSURE (in. wg)
Fig. 28 --- Barometric Flow Capacity
30
25
20
15
10
5
0
0.13 0.20 0.22 0.25
STATIC PRESSURE (in. wg)
Fig. 29 --- Outdoor- -Air Damper Leakage
sensors (HH57AC078
0.15 0.25
C06030
0.30 0.35 0.40 0.45 0.50
C06031
6000
5000
4000
3000
2000
1000
0
0.05
Fig. 30 --- Return- -Air Pressure Drop
and
Fig. 31 --- Enthalpy Sensor and Mounting Plate
SUPPLY AIR
TEMPERATURE
SENSOR
MOUNTING
LOCATION
SUPPLY AIR
TEMPERATURE
SENSOR
Fig. 32 --- Supply Air Sensor Location
27
0.10 0.15 0.20 0.25
STATIC PRESSURE (in. wg)
HH57AC078 ENTHALPY
SENSOR
MOUNTING PLATE
0.30 0.35
C06032
C 7 4 0 0
A 1 0 0 4
C06361
C06033