Selecting Door-Mounted Control Devices for

Application Bulletin
Altivar 66 AC Drive
This Application
Note explains when
to select doormounted control
devices without a
manual speed
potentiometer for
Class 8839 Enclosed
ALTIVAR 66 drives.
Selecting Door-Mounted Control Devices
Door-Mounted Control Devices
Without Manual Speed Potentiometer
Mod Number
Start/Stop Push Buttons
Start/Stop Push Buttons and Hand-Auto Switch
Stop Push Button and Forward/Reverse Push Buttons
Run/Stop Switch
Forward/Off/Reverse Switch
Hand/Off/Auto Switch
When should you select door-mounted control devices without a
manual speed potentiometer for Class 8839 Enclosed ALTIVAR 66
drives? Before choosing a general purpose device, ask yourself,
“How will the speed of the drive be controlled without a local manual
speed potentiometer?”
Correct Reasons:
• Manual speed potentiometer will be remote mounted from the
• Increase/decrease speed switches will be remote mounted from
the drive.
Incorrect Reasons:
• Manual speed is controlled with a keypad, eliminating the need
for the manual speed potentiometer. (See “Keypad versus
Terminal” mode below.)
• Manual speed potentiometer is assumed to be standard on the
• Perceived cost savings of a manual speed potentiometer is offset
by expensive field rework costs.
Keypad Versus Terminal Mode
The Class 8839 Enclosed ALTIVAR 66 AC Drives are configured from
the factory to operate in the Terminal mode. This mode activates the
logic and analog inputs for interfacing with isolation/bypass
contactors, process sequencing, and analog speed reference signals.
NOTE: Switching from Terminal mode to Keypad mode disables all the I/O
wired to the terminal strips, making external sequence logic inoperable.
Application Bulletin
Altivar 66 AC Drive
Selecting Door-Mounted Control Devices (continued)
The keypad is used primarily to program drive parameter functions
and to display operational diagnostics.
For example, a field sales representative specifies Mod “L09-Hand/
Off/Auto Selector Switch” for an enclosed AC Drive that has an
isolation and bypass scheme. Hoping to save on unit cost, the keypad
is used to adjust the speed instead of a door-mounted manual speed
The Bill of Material consists of:
Class 8839 Type 66UHG4VC (10HP @ 460 V)
LO9-Hand/Off/Auto Selector Switch
A11-24 V I/O Extension Module
The right reason to specify this configuration:
The end user plans to wire a remote 2.5kΩ speed potentiometer to
control the drive in the Hand position.
The wrong reason to specify this configuration:
Using the keypad mode to control the drive will disable all external
I/O required by the drive to operate. In this mode, neither isolation
and bypass sequencing nor any remote interlocks will operate.
July, 1996
Raleigh, NC, USA
ALTIVAR is a trademark of Telemecanique S.A. or its successor-in-interest, Schneider Electric S.A.
© 1996 Square D All Rights Reserved
Electrical equipment should be serviced only by qualified electrical maintenance personnel. No
responsibility is assumed by Square D for any consequences arising out of the use of this material.