Bryant Preferred 581J04-14, Service And Maintenance Instructions, Page: 50 / 148

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enthalpy to the return air enthalpy to determine EconoMi$er IV
use. The controller selects the lower enthalpy air (return or out-
door) for cooling. For example, when the outdoor air has a
lower enthalpy than the return air, the EconoMi$er IV opens to
bring in outdoor air for free cooling.
Replace the standard outside air dry bulb temperature sensor
with the accessory enthalpy sensor in the same mounting loca-
tion. See Fig. 75. Mount the return air enthalpy sensor in the
return air duct. See Fig. 74. Wiring is provided in the
EconoMi$er IV wiring harness. See Fig. 67. The outdoor en-
thalpy changeover set point is set with the outdoor enthalpy set
point potentiometer on the EconoMi$er IV controller. When
using this mode of changeover control, turn the enthalpy set
point potentiometer fully clockwise to the D setting.
Fig. 76 — Enthalpy Changeover Set Points
INDOOR AIR QUALITY (IAQ) SENSOR INPUT
The IAQ input can be used for demand controlled ventilation
control based on the level of CO
2
measured in the space or re-
turn air duct.
Mount the accessory IAQ sensor according to manufacturer
specifications. The IAQ sensor should be wired to the AQ and
AQ1 terminals of the controller. Adjust the DCV potentiome-
ters to correspond to the DCV voltage output of the indoor air
quality sensor at the user-determined set point. See Fig. 77.
Fig. 77 — CO
2
Sensor Maximum Range Settings
If a separate field-supplied transformer is used to power the
IAQ sensor, the sensor must not be grounded or the
EconoMi$er IV control board will be damaged.
When using demand ventilation, the minimum damper position
represents the minimum ventilation position for VOC (volatile or-
ganic compounds) ventilation requirements. The maximum de-
mand ventilation position is used for fully occupied ventilation.
When demand ventilation control is not being used, the mini-
mum position potentiometer should be used to set the occupied
ventilation position. The maximum demand ventilation posi-
tion should be turned fully clockwise.
EXHAUST SET POINT ADJUSTMENT
The exhaust set point will determine when the exhaust fan runs
based on damper position (if accessory power exhaust is in-
stalled). The set point is modified with the Exhaust Fan set
point (EXH SET) potentiometer. See Fig. 71. The set point rep-
resents the damper position above which the exhaust fans will
be turned on. When there is a call for exhaust, the EconoMi$er
IV controller provides a 45 ± 15 second delay before exhaust
fan activation to allow the dampers to open. This delay allows
the damper to reach the appropriate position to avoid unneces-
sary fan overload.
MINIMUM POSITION CONTROL
There is a minimum damper position potentiometer on the
EconoMi$er IV controller. See Fig. 71. The minimum damper
position maintains the minimum airflow into the building
during the occupied period.
When using demand ventilation, the minimum damper position
represents the minimum ventilation position for Volatile Or-
ganic Compound (VOC) ventilation requirements. The maxi-
mum demand ventilation position is used for fully occupied
ventilation.
When demand ventilation control is not being used, the mini-
mum position potentiometer should be used to set the occupied
ventilation position. The maximum demand ventilation posi-
tion should be turned fully clockwise.
Adjust the minimum position potentiometer to allow the mini-
mum amount of outdoor air, as required by local codes, to enter
the building. Make minimum position adjustments with at least
10°F temperature difference between the outdoor and return-
air temperatures.
To determine the minimum position setting, perform the fol-
lowing procedure:
1. Calculate the appropriate mixed air temperature using the
following formula:
T
O
= Outdoor-Air Temperature
OA = Percent of Outdoor Air
T
R
= Return-Air Temperature
RA = Percent of Return Air
T
M
= Mixed-Air Temperature
As an example, if local codes require 10% outdoor air during
occupied conditions, outdoor-air temperature is 60°F, and re-
turn-air temperature is 75°F.
(60 x 0.10) + (75 x 0.90) = 73.5°F
2. Disconnect the supply air sensor from terminals T and T1.
3. Ensure that the factory-installed jumper is in place across
terminals P and P1. If remote damper positioning is being
used, make sure that the terminals are wired according to
Fig. 71 and that the minimum position potentiometer is
turned fully clockwise.
4. Connect 24 vac across terminals TR and TR1.
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
14
16
1
8
20
2
2
2
4
2
6
28
30
32
3
4
3
6
38
40
42
4
4
46
9
0
1
0
0
80
7
0
60
50
40
30
20
10
E
NTHALPY
BTU PER
POUN
D DRY
AI
R
85
(29)
90
(32)
95
(35)
100
(38) 105
(41) 110
(43)
3 5
(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
RELA
TI
VE HUMI
DI
TY (
%
)
HIGH LIMIT
CURVE
APPROXIMATE DRY BULB TEMPERATURE--degree s F (degree s C)
0
1000
2000
3 000
4000
5000
6000
2 3 4 5 6 7 8
RANGE
C
ONFIGURA
TION
(ppm)
DAMPER VOLTAGE FOR MAX VENTILATION RATE
CO S EN S OR MAX RANGE S ETTING
2
8 00 ppm
900 ppm
1000 ppm
1100 ppm
(T
O
OA
) + (T
R
x
RA
) = T
M
100 100
x