Greenheck AMD-xx-TD Series Dampers (478799 IOM). - Manual (Page 5)

5
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.
Figure 3
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 Dampers with a BACnet Enabled Factory Supplied Controller
Figure 3 shows field wiring for an AMD-TD ordered with a factory supplied controller configured for a BACnet
MS/TP connection.
1 2 3 4 5 6 9 7 8
~

+ -
24VAC
Factory Installed
Terminal Block
Factory
Installed
Jumper
BACnet
MS/TP
AMD-XX-TD w/BACnet
MS/TP Factory
Supplied Controller
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 BACnetSetpoint 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)
BACnetSetpoint = (Target CFM / Maximum CFM)
BACnetSetpoint = (6,000 / 8,000) = 75%
With a BACnetSetpoint 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
BACnetSetpoint 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 BACnetSetpoint 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.