Bryant 549B - Manual (Page 167)

167
APPLICATION DATA (cont)
IAQ sensors — EconoMi$erIV can be utilized with any IAQ
(CO
2
) sensor that provides a 2 to 10 vdc output. The con-
troller will modulate the outdoor air damper to provide venti-
lation based on the sensor output and the IAQ setting of the
controller. When used, an IAQ sensor will modulate the
damper from the minimum position (base ventilation rate
based on CO
2
levels) to maximum position (full occupancy
ventilation rate).
Damper operation — The EconoMi$erIV allows the damper
to be configured for two adjustable damper positions includ-
ing maximum position and occupied minimum positions.
The two (2) position damper capability is a unique feature of
EconoMi$erIV and includes operation flexibility as follows:
1. Minimum Occupied Position: This adjustable position
allows a minimum ventilation airflow rate through the unit
during occupied periods (base ventilation rate).
2. Demand Control Ventilation (DCV) Maximum Position: A
DCV maximum occupied position is provided when using
an IAQ sensor for DCV. See DCV and Control sections
for sequence. The DCV Maximum Position limits outdoor
airflow into the rooftop when the DCV routine overrides
the mixed air sensor. Setting the DCV Maximum Position
of the outdoor-air damper prevents large amounts of hot
or cold air into the space.
IMPORTANT: When the DCV Maximum Position is set
below the minimum position, the minimum position over-
rides the maximum position, negating most DCV functions.
Compressor staging — The EconoMi$erIV is an integrated
economizer and has the ability to utilize simultaneous out-
door air and compressors. The EconoMi$erIV can be con-
figured to support economizer and compressor operation
for up to 4 compressors. Only one or two compressor oper-
ation is available with 3 to 12
1 /
2
ton units.
CHANGEOVER STRATEGIES — The EconoMi$erIV con-
troller can be configured to accommodate all available
economizer control strategies that place the rooftop unit in
economizer mode including:
Switch — Used when a remote signal from an energy man-
agement system will enable and disable the EconoMi$erIV
(remote enable control).
Outdoor dry bulb — EconoMi$erIV will be enabled based
on the outside air temperature. This is provided standard
with the EconoMi$erIV.
Differential dry bulb — EconoMi$erIV will be enabled when-
ever the outside air temperature is lower than the return-air
temperature.
CONTROL
CURVE
A
B
C
D
CONTROL POINT
APPROX. °F (°C)
AT 50% RH
73 (23)
70 (21)
67 (19)
63 (17)
12
14
1
6
18
20
2
2
24
26
28
30
32
34
36
38
40
42
44
46
90 10
0
80
70
60
50
40
30
20
10
ENT
HA
LP
Y—
BTU
P
ER
PO
UN
D DR
Y A
IR
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)
APPROXIMATE DRY BULB TEMPERATURE— °F (°C)
A
A
B
B
C
C
D
D
REL
AT
IVE HU
M
IDIT
Y
(%
)
HIGH LIMIT
CURVE
Economizer Changeover Curves
a50-7751