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Table 118 — VFD Terminal Designations
TERMINAL
U1 / L1
V1 / L2
Three-phase main circuit input power supply
W1 / L3
U2 / T1/U
Three-Phase AC Output to Motor,
V2 / T2/V
0-v to Maximum Input Voltage Level
W2 / T3/W
X1-11 (GND)
Factory-supplied jumper
X1-12 (D-COM)
X1-10 (+24 V)
Factory-supplied jumper
X1-13 (DI-1)
X1-10 (+24 V)
Start Enable 1 (Factory-supplied jumper).
When opened the drive goes to emergency stop.
X1-16 (DI-4)
X1-28 (SCR)
X1-29 (B+)
Factory wired for local equipment network LEN
X1-30 (B-)
communication
X1-31 (AGND)
X1-32 (SCR)
VFD POWER EXHAUST
On units equipped with VFD power exhaust, both power exhaust
fan motors are controlled by a single VFD. Fans are turned on by
the ComfortLink controls based on building pressure sensed by
the building pressure transducer. The VFD fan speed is controlled
by the ComfortLink controls. The power exhaust fan motors are
each protected by a motor starter protector located in an enclosure
below the power exhaust VFD. The required motor starter protec-
tor settings are shown on a label on the cover of the enclosure.
HIGH CAPACITY POWER EXHAUST (SIZES 075-100
ONLY)
The power exhaust fans are two belt-driven forward-curved fans.
Operation of the power exhaust is a combination modulating/
staged control. The lead fan is controlled by a VFD and provides
0 to 50% of total exhaust capability. The second fan is staged
On/Off (for a step of 50% of total exhaust capability) according
to the VFD output level on fan no. 1.
RETURN FAN
The return fan power exhaust assembly consists of one belt-drive
plenum fan. The plenum fan pressurizes the plenum fan section so
that air can either be discharged horizontally out the back of the
unit or discharged through the return air section of the economizer.
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14
15
Fig. 36 — VFD Wiring
FUNCTION
Terminal X1
16
17
18
LEN connection from ComfortLink
ECONOMIZER MOTOR(S)
The economizer outside air and return air dampers are gear-driven
dampers without linkages. A communicating economizer mo-
tor(s) controls their position. The motor position is controlled by
the MBB through the communication bus. This allows for accu-
rate control of the motors as well as feedback information and di-
agnostics information. The control has a self-calibration routine
that allows the motor position to be configured at initial unit start-
up. The motor(s) is located on the economizer and can be reached
through the filter access door.
THERMISTORS AND PRESSURE TRANSDUCERS
The unit is equipped with several thermistors for measurement of
temperatures. The thermistors are summarized in Table 119.
The units have two pressure transducers that are connected to the
low side of the system. These two pressure transducers measure
the low side pressure and are used for low pressure protection and
coil freeze protection.
The units also have two pressure transducers that are connected to
the high side of the system. These two pressure transducers mea-
sure the discharge pressure and are used to cycle the condenser
fans to maintain head pressure.
By using the high and low side pressure transducers, the
ComfortLink controls display the high and low side pressures and
saturation temperatures and a normal gauge set is not required.
SMOKE DETECTOR
The units can be equipped with an optional smoke detector lo-
cated in either the return air or supply air, or in both. The detec-
tor is wired to the ComfortLink controls and, if activated, will
stop the unit by means of a special fire mode. The smoke detec-
tor can also be wired to an external alarm system through TB201
terminals 1 and 2. The sensor is located in the air section.
FILTER STATUS SWITCH
The units can be equipped with an optional filter status switch.
The switch measures the pressure drop across the filters and closes
when an adjustable pressure set point is exceeded. The sensor is
located in the return air section behind the filter access door.
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