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VARIABLE SPEED FAN
The terminal unit fan speed will be controlled through
When initially powered up, or upon restoration of power after a power outage, the
executes a fan startup sequence to prevent reverse rotation. The fan startup sequence drives the primary air
damper closed, waits 30 seconds, and then sets the fan speed output to 100% for 2 seconds. The controller
will then set the fan speed output to the current fan setpoint,
Fan Speed Calculation
For variable speed fans,
demand percent to the range from min to max fan speed. For instance, with a Cooling demand of 50% and
a series fan with a min (deadband) fan speed setpoint of 20% and a maximum (cool stpt) fan speed setpoint
of 70%,
EffFanSpeedCmd
Fan Speed Setpoint Range: 70 % max – 20 % min = 50 %
Cool Demand = 50 %
50 % demand X 50 % range = 25% signal
EffFanSpeedCmd
EffFanSpeedCmd
PARALLEL VARIABLE SPEED FAN
The Parallel Variable Speed fan will be energized when the
not in the heat mode. Speed will modulate between the Minimum and Maximum Setpoints as shown below.
100
90
80
70
60
Max Heat
50
40
30
20
10
0
68 68.5 69 69.5 70 70.5 71 71.5 72 72.5 73 73.5 74
•
Max Heat Fan Speed Setpoint is
•
Min Heat Fan Speed Setpoint is
•
Min Fan Speed Setpoint is
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Subject to change without notice
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CBV-2U4-3T(-N) |
EffFanSpeedCmd
(A176) is determined by translating the current Cool or Heat
(A176) is calculated as follows:
(A176) = signal + min
(A176) = 25% + 20% = 45%
Occupied Fan Speed Stp %
Min
Heat
TABFanHtgMaxStpt
TabFanHtgMinStpt
TABFanDbandStpt
(A224)
Control Sequence Overview
(0
...
10 V dc, 2
...
10 V dc, or a custom range).
AO-15
EffFanSpeedCmd
(A176.)
CBV-2U4-3T(-N)
is in the heat mode and off when
Deadba
nd
(A226)
(A154)
CBV-2U4-3T(-N)
controller
Speed Stpt
59
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