The controller is designed to modulate the AMD-xx-
TD series damper such that it maintains a desired
cfm setpoint. The setpoint is supplied via a 0-10 VDC
analog input (terminals 5 and 6) that is proportional to
that setpoint. The Vari-Green transmitter will output
a 0-10 VDC signal (terminals 3 and 4) proportional to
the actual cfm being measured by the unit. For both
the desired cfm setpoint and the cfm output, a voltage
reading of 10 VDC represents the
maximum
velocity
that was selected at the time the product was ordered.
The selected maximum velocity and the area of the
AMD-xx-TD are listed on a label adjacent to the terminal
block. Example 2 shows how to determine the voltage
corresponding to the desired cfm setpoint.
Example 2:
Determine the voltage setpoint that should be sent to
terminals 5 & 6 to achieve a flow of 4,800 CFM on a 24
in. x 24 in. AMD-xx-TD (area of 4 ft
2
) with a selected
maximum velocity of 2,000 fpm.
Maximum CFM =
4
ft2 * 2,000 fpm = 8,000 cfm
Voltage Setpoint =
10 * (Desired CFM Setpoint /
Maximum CFM)
Voltage Setpoint =
10 *(4,800 / 8,000) = 6.0 VDC
See example 1 on how to convert the transmitter
voltage output (terminals 3 & 4) to cfm.
AMD-xx-TD Series Damper with a BACnet
Enabled Factory Supplied Controller
Figure 3
shows field wiring for an AMD-xx-TD ordered
with a factory supplied controller configured for BACnet
MS/TP connection.
1 2 3 4 5 6
9
7 8
~
D
+ -
24VAC
Factory Installed
Terminal Block
Factory
Installed
Jumper
BACnet
MS/TP
AMD-XX-TD w/BACnet
MS/TP Factory
Supplied Controller
Figure 3
This controller is designed to modulate the AMD-xx-
TD series damper such that it maintains a desired
cfm setpoint. The setpoint is established by the
BACnetSetpoint
datapoint. Table 1 lists all of the BACnet
datapoints. The
BACnet Setpoint
is a percentage of the
MaxCFMSetpoint
datapoint, which is set at the factory
based on the maximum velocity which is selected at the
time the unit is ordered.
Example 3:
Determine the BACnet setpoint for a 24
in. x 24 in. AMD with a maximum velocity of 2,000 fpm
and a target flow of 6,000 cfm.
MaxCFMSetpoint =
8,000 cfm (4 ft2 x 2,000 fpm)
BACnet Setpoint =
(Target CFM / Maximum CFM)
BACnet Setpoint =
(6,000 / 8,000) = 75%
With a
BACnet Setpoint
of 75% the actuator/controller
will position the damper to allow 6,000 cfm through it.
Position Control Mode
Example 3 applies when the actuator/controller is
in its factory default operating mode called “Flow
Control Mode”. However, for certain applications it may
be desirable to operate the AMD-TD as a standard
modulating damper. This can be accomplished by
changing the
DamperMode
BACnet data point (see
Table 1
) from
CurrentAirflow
to
DamperPosition
. In
“Position Control Mode” a
BACnet Setpoint
of 75% will
drive the damper 75% open instead of finding a position
that supplies 75% of the maximum airflow.
Safety Override of the BACnet Setpoint
If your application requires the ability to locally close
the damper, the factory installed jumper wire should be
removed and replaced with a normally closed “safety
switch”. When the safety switch is closed the damper
will track the
BACnet Setpoint
as if the jumper wire was
left in place. When the safety switch is open the actuator
will power the damper closed. Interlocking the damper
with a fan such that the damper closes when the fan
shuts down is an example of when the safety switch
feature may be utilized.
AMD-xx-TD Series
5
