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*N = Quantity of Registers
Response
Function code
1 Byte
Starting Address
2 Bytes
Quantity of Registers
2 Bytes
Error
Error code
1 Byte
Exception code
1 Byte
0x01 = Unsupported Function Code
0x02 = Invalid Register Address
0x03 = Register Value Outside Specified Range
0x04 = Register Write Failed. This will occur if the
incorrect access level password was applied in register
200.
Minimum Communication Requirement
If no Modbus communication is received by the drive
f or 30 seconds the drive will issue a Modbus
Communications Lost error. A best practice is to
provide a "heartbeat" signal every 100ms. An example
of this would be a read command of drive status
register #5 every 100ms. Bit #2 will give you the status
of the drive. 0: Ok | 1: Faulted
Special Function
This f unction is used to perform special functions on
the drive. See the Modbus Map section in the
Addendum for additional details.
Input Voltage and Input Current
The drives are designed f or an input power supply of
208 to 240 volts 50/60 Hz. Published performance of the
drive and compressor combination will have a
perf ormance tolerance specified on the compressor
perf ormance data sheet when the drive input voltage is
in the range of 208 to 240 volts.
Emerson Classification:
Internal
6
© 2023 Emerson Climate Technologies, Inc.
0x10
Power Factor Correction
0x0000 to
0xFFFF
The drive incorporates active power f actor correction.
There are 3 states of power factor correction, off, partial,
0x0000 to
and on. The drive will automatically switch between the
0x007B
various states in order to maximize system efficiency.
Contact Application Engineering for additional details.
Compressor & Fan Motor Speed Control
0x90
The EVA3 drive controls both the compressor &
condensing f an speed. Both speeds are controlled by
0x01
writing the speed demand to the appropriate Modbus
register. The compressor and f an may be operated
0x02
independent of each other. The maximum and minimum
allowed speeds f or the compressor can be read from
0x03
registers 3 & 4 respectively. These speeds may vary
0x04
based upon the selected compressor. Similarly, the
maximum and minimum allowed speeds for the selected
condensing fan can be read from registers 1003 & 1004.
Start-up
The drive will not start with f aults present. Modbus
registers 78 through 85, and 1078 to 1081 should all be
equal to 0, this can also be verified by checking register
5, bit 2. To clear f aults, see the Fault Clearing section.
Use the steps below in order to start the compressor /
condensing fan.
Start-up control is divided into 3 stages. For a detailed
description, refer to Addendum for start-up procedures
and requirements. Af ter successful start-up, the
compressor and fan will run at the demanded speed.
The condenser f an to be always started f irst before
compressor start-up. Register 1005, bit-8 can be
monitored to ensure condenser f an has reached
demanded speed before starting the compressor.
Drive
Max AC Input Current
EVA3042B
18.5A RMS
EVA3071B
31.0A RMS
1. Enable drive by writing '1' to Modbus register
100.
2. Write compressor target RPM to Modbus
register 101.
3. Write the f an target RPM to register 1101 (if
applicable).
AE8-1435
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