17
Setting Fan Air Flow with ECM Motors
Several terminal unit models are available with ECM motors for
easy balancing. These motors supply a determined amount of air
regardless of static pressure from ductwork layout or air distribu
-
tion. The ECM motors are programmed to provide a maximum
cfm depending on model and unit size. The motors are then set to
provide the desired cfm as a proportional amount of the maxi
-
mum. The proportion can be set by several options:
VCU (CONTROL OPTION 6)
VCU controlled units are manually operated with a digital readout
on the ECM controller (see Fig.
12). The digital readout provides a
percent of maximum. A fan adjustment knob is rotated until the
desired percent is displayed. After 20 seconds from final adjust-
ment, the controller display will alternate between percent and
motor RPMs. See Tables
15-29 for the percent required for desired
CFM.
Fig. 12 — VCU ECM Controller
ACU-O, 0-10VDC (0-20MA) INPUT
(CONTROL OPTION 7)
The board is factory set to accept a 0-10 Vdc signal to control the
airflow between 0% and 100% as shown in the chart in Fig.
12.
This option does not allow for on/off control. Setting the jumper to
the “Opt” position as shown in the “Jumper Setting” in Fig.
13 sets
the control signal to 0-10 Vdc signal.
Fig. 13 — ACU ECM Controller
ACU-P, 2-10VDC (4-20MA) INPUT (CONTROL OPTION 8)
Another option is to have the board factory set to allow for on/off
control by setting the jumper on to the “P” position. This setting
uses a 2-10 Vdc control signal range with a voltage signal under
2
Vdc turning the motor off. See Fig. 13 for graph of operating
range.
NOTE: Both ACU Options provide a manual Override
for field setting the ECM motor without being connected
to a DDC controller. If a DDC controller is connected,
adjusting the manual override with lock out the
automation signal for 15 minutes.
Volts
0-10Vdc 2-10Vdc with
On/Off
“Opt” Jumper
“P” Jumper
10
9
8
7
6
5
4
3
2
1
0
0 10 20 30 40 50 60 70 80 90 100
Flow Index
JUMPER SETTING
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