ABB ACS320 Supplemental Manual page 3

"ON" AND "SPEED" SIGNALS
VFD operation in this unit is dependent on two signals: an ON signal and a SPEED (or REFERENCE) signal.
The sources and types of these signals can vary. If the ERV is equipped with dampers the ON signal to the
VFD comes from the end switch on the damper. If the ERV is not equipped with dampers, the ON signal
comes from an external control connected directly to the VFD. When an ON signal is received by the VFD,
it starts the motor. The VFD then operates the blower at the speed established by the SPEED signal. The
SPEED signal is often provided by an external control, but in some applications "pre-set" speeds are set
inside the VFD and are selected by external switches or relays.
PRINCIPLES OF EXTERNAL CONTROL
This ERV can be operated by various external
control devices including remote switch or relay,
digital time clock with relay, occupancy sensor
with relay, and carbon dioxide sensor with relay
and analog output. These devices are commonly
known as 2-wire, 3-wire, and 4-wire devices.
A Building Management System (BMS) can control
this ERV through relay contacts and with 0-10vdc
or 4-20mA analog inputs.
The external control devices can be connected to
this ERV to operate each blower independently or
CONNECTING EXTERNAL CONTROLS
If this ERV is equipped with damper(s), the ON signal is connected to the terminal strip in the electrical
enclosure ("E-box"). If this ERV is not equipped with damper(s), and has 2 VFDs, the ON signal is
connected directly to the VFDs. The SPEED signals are always connected directly to the VFD(s).
WIRE ROUTING
Route input power cables, motor cables and control
cables separately to decrease electromagnetic
interference caused by the rapid changes in
the drive output voltage. Where control cables
must cross power cables make sure that they
are arranged at an angle as near to 90 degrees
as possible. See the ABB VFD manual for more
detailed wire routing instructions.
Power cables and control cables can be brought
into the bottom of the electrical box attached to the
ERV unit or through the bottom of the unit itself.
There are plugged holes to run control wires and
power wires between the electrical box and the
unit interior, marked on the interior of the ERV unit
and another plugged hole in the unit compartment
divider to run wires to VFDs in the other airstream
compartment if needed.
ABB VARIABLE FREQUENCY DRIVES
for one blower to act as leader and the other
blower to act as follower. In leader-follower
mode, a single external switch or relay calls for
operation and the leader VFD sets SPEED to internal
presets, or in response to an analog input signal.
The follower VFD then operates at either exactly
the same speed, at an offset above or below the
leader's speed, or at a scaled speed.
The VFD's are pre-programmed at the factory so
only a few parameters need change for a
specifi c installation.
In some confi gurations the VFD and/or VFD
protective guard may need to be removed to
access the control wire hole plug to run wires.
A label is located in the ERV on the left interior
wall indicating the power and control wire hole
plug locations. Bring wires out from the top or
bottom of the VFD mounting bracket and not
through the mounting bracket window when
routing wires if |the VFD is mounted over the
hole plug.
After the wires are run, apply caulk around the
wires at wire bushings used between the electrical
box and ERV unit and between compartments
in the unit to prevent air leakage between these
compartments.
1.800.627.4499
INSTALLATION
PLANNING YOUR
INSTALLATION
ABB VFD SUPPLEMENTAL MANUAL RENEWAIRE.COM 3