Carrier WeatherMaster 50HC04 Service And Maintenance Instructions page 38

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. 74 — Enthalpy Changeover Set Points
INDOOR AIR QUALITY (IAQ) SENSOR INPUT
The IAQ input can be used for demand control ventilation con-
trol based on the level of CO
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. 75.
CO SENSOR MAX RANGE SETTING
2
6000
5000
4000
3000
2000
1000
0
2 3 4
DAMPER VOLTAGE FOR MAX VENTILATION RATE
Fig. 75 — CO Sensor Maximum Range Settings
2
If a separate field-supplied transformer is used to power the
IAQ sensor, the sensor must not be grounded or the
EconoMi$er IV control board will be damaged.
When using demand ventilation, the minimum damper position
represents the minimum ventilation position for VOC (volatile or-
ganic compounds) ventilation requirements. The maximum de-
mand ventilation position is used for fully occupied ventilation.
When demand ventilation control is not being used, the mini-
mum position potentiometer should be used to set the occupied
ventilation position. The maximum demand ventilation posi-
tion should be turned fully clockwise.
85 90 95 100 105 110
(29) (32) (35) (38) (41) (43)
80
(27)
75
(24)
70
(21)
65
A
B
C
D
65 70 75 80 85 90 95 100 105 110
(18) (21) (24) (27) (29) (32) (35) (38) (41) (43)
measured in the space or return
2
800 ppm
900 ppm
1000 ppm
1100 ppm
5 6 7 8
EXHAUST SET POINT ADJUSTMENT
The exhaust set point will determine when the exhaust fan runs
based on damper position (if accessory power exhaust is in-
stalled). The set point is modified with the Exhaust Fan set
point (EXH SET) potentiometer. See Fig. 69. The set point rep-
resents the damper position above which the exhaust fans will
be turned on. When there is a call for exhaust, the EconoMi$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$er IV controller. See Fig. 69. The minimum damper
position maintains the minimum airflow into the building
during the occupied period.
When using demand ventilation, the minimum damper position
represents the minimum ventilation position for Volatile Or-
ganic Compound (VOC) ventilation requirements. The maxi-
mum demand ventilation position is used for fully occupied
ventilation.
HIGH LIMIT
CURVE
When demand ventilation control is not being used, the mini-
mum position potentiometer should be used to set the occupied
ventilation position. The maximum demand ventilation posi-
tion should be turned fully clockwise.
Adjust the minimum position potentiometer to allow the mini-
mum amount of outdoor air, as required by local codes, to enter
the building. Make minimum position adjustments with at least
10°F temperature difference between the outdoor and return-
air temperatures.
To determine the minimum position setting, perform the fol-
lowing procedure:
1. Calculate the appropriate mixed air temperature using the
following formula:
(T
T
= Outdoor-Air Temperature
O
OA = Percent of Outdoor Air
T = Return-Air Temperature
R
RA = Percent of Return Air
T = Mixed-Air Temperature
M
As an example, if local codes require 10% outdoor air during
occupied conditions, outdoor-air temperature is 60°F, and re-
turn-air temperature is 75°F.
(60 x 0.10) + (75 x 0.90) = 73.5°F
2. Disconnect the supply air sensor from terminals T and T1.
3. Ensure that the factory-installed jumper is in place across
terminals P and P1. If remote damper positioning is being
used, make sure that the terminals are wired according to
Fig. 69 and that the minimum position potentiometer is
turned fully clockwise.
4. Connect 24 vac across terminals TR and TR1.
5. Carefully adjust the minimum position potentiometer until
the measured mixed air temperature matches the calcu-
lated value.
6. Reconnect the supply air sensor to terminals T and T1.
Remote control of the EconoMi$er IV damper is desirable
when requiring additional temporary ventilation. If a field-sup-
plied remote potentiometer (Honeywell P/N: S963B1128) is
wired to the EconoMi$er IV controller, the minimum position
of the damper can be controlled from a remote location.
To control the minimum damper position remotely, remove the
factory-installed jumper on the P and P1 terminals on the
EconoMi$er IV controller. Wire the field-supplied potentiometer
38
OA RA
) + (T ) = T
x
x
O
100 100
R
M