Emerson EVH Series, Installation Manual

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Bypass setup/operation
This section describes the basic operation allowing the unit to start/stop the motor in bypass and under VFD control. Refer to
the Application Manual to become familiar with the VFD Keypad operation and VFD Menu Structures.
Bypass options
There are several bypass power and control options that are defined by the catalog number nomenclature: 2 Contactor
Bypass, VFD Isolation Contactor and VFD Isolation Switch and Manual Bypass Switch. See options sections for
description/operation.
VFD parameter settings
Bypass Designs have several parameters that were reset to operate the bypass controls correctly. If these parameters are
changed either Manually or Automatically (using the “Load Parameter Set” function P13.1.3), the bypass control circuit may
not operate properly!
The key bypass design parameters are:
P2.2.3 IO terminal 1 Start Signal 2 must be set to DigIN:NormallyOpen
P2.2.6 IO terminal 2 Start Signal 2 must be set to DigIN:NormallyOpen
P2.2.9 Ext Fault 1 NO must be set to DigIN 3
P2.2.19 Run Enable must be set to DigIN 2
P2.2.34 Bypass Start must be set to DigIN 7
P3.1.2 RO1 Function must be set to BYPASS Run
P3.1.5 RO2 Function must be set to RUN
P3.1.8 RO3 Function must be set to FAULT
P10.1.1 Bypass Enable is set to ENABLE
P10.1.2 Bypass Start Delay is set to 1 sec
P10.1.3 Auto Bypass Start is set to DISABLE
Bypass modes of operation
Bypass designs have three modes of operation: VFD, OFF or BYPASS.
VFD mode, the motor is powered by the VFD and motor speed is adjustable. The motor may or may not be running depending
on the controls.
BYPASS mode, the motor connected across the line and motor speed is fixed at base speed.
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