How to Guide

Commercial Pressure and Float Switches for Power Circuits
Float Switches—Class 9036, 9037, and 9038
59
03/2011
© 2011 Schneider Electric
All Rights Reserved
Class 9038 Type A Mechanical Alternators
Class 9038 mechanical alternators provide a simple, positive means of mechanically alternating two
pumps or motors. These alternators are used on devices that are installed in a duplex system with a
common tank. There are three types of Class 9038 mechanical alternators:
• Type A (open tank and sump)
• Type C (with bushing)
• Type D (flange mounted, vertical)
When liquid level rises to the first level, one pump turns on. Both pumps automatically turn on when a
peak condition occurs and the liquid level continues to rise. If Form N5 or N25 is present, and the water
level continues to rise, a high water alarm is activated.
Mechanical alternators can be ordered with a manual transfer selector switch (Form N3), which allows
the operator to select which pump cuts in first. The second pump only operates under peak demand
conditions or if the first pump fails. When the switch is disengaged, the alternator reverts to normal
operation. Another option (Form N4) allows the alternator to be used as a two-level non-alternating unit.
Class 9038 Type A Open and Sump Tank Mechanical Alternators
Table 21 contains ordering information for Class 9038 Type A mechanical alternators, including factory
installed modifications. Order float accessories separately. Contact the Sensor Competency Center
when using Class 9038 alternators in liquids with a different specific gravity than water (1.0).
When ordering a factory modification, add the Form number to the end of the mechanical alternator
catalog number. For example, to select a 9038AG1 alternator with reverse action, order 9038AG1R.
Table 21: Class 9038 Type A Mechanical Alternators
Specifications
Application Open and sump tanks using duplex pumps
Float Movement Float operated
Ambient Temperature –22 to +200 °F
Contact Operation
Close on liquid rise (standard)
Open on liquid rise (Form R)
Catalog Numbers
NEMA 1 9038AG1
NEMA 4 (compensating spring standard) 9038AW1
NEMA 7, 9 (compensating spring standard) 9038AR1
Modifications
NOTE: Factory installed only.
Form
Compensating spring (Type AG) C (field installable)
Two-level, non-alternating unit N4
High water alarm circuit (single pole) N5
High water alarm circuit (two pole) N25
Reverse action: contacts open on liquid rise R
Accessories Catalog Number
Compensating spring (Type AG) 9049A15
9038AG1