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The performance specifications are nominal and conform to acceptable industry standards. For applications at conditions beyond these specifications, consult the local Johnson Controls office.
Johnson Controls, Inc. shall not be liable for damages resulting from misapplication or misuse of its products. © 2015 Johnson Controls, Inc. www.johnsoncontrols.com
R-61
A28 Series Two-Stage Flange Mounted Duct Thermostat
Description
The A28AK is a two-stage temperature
control with special air coil sensing element
and adjustable mounting flange.
Refer to the A28 Series Two-Stage
Temperature Controls with NEMA 1
Enclosure Product Bulletin (LIT-125130) for
important product application information.
Action on Increase
of Temperature
Y
B
R
Y
B
R
A28 Series
Low Stage
High Stage
a28.eps
A28 Action Diagram
Features
flat flange mounting with special coil
element permits positioning of sensing bulb
in the appropriate portion of the air stream
two single-pole, double-throw (SPDT)
snap-acting switches
unaffected by barometric pressure or cross
ambient temperatures
Applications
These duct thermostats are used on roof top
units, make-up heaters, duct heaters, and air
handling systems of all types.
Selection Chart
Technical Specifications
Note: When used as a two-circuit control, the total connected load must not exceed 2,000 VA.
Product Code
Number
Number
of Stages
Switch
Action
Range °F (°C) Differential F° (C°) Fixed Maximum Allowable
Temperature at Bulb
°F (°C)
Each
Stage
Between
Stage
A28AK-1C Two Two-SPDT switches 30 to 110
(-1 to 43)
2 (1.1) 3 (1.7) 140 (60)
A28AK-2C Two Two-SPDT switches 60 to 130
(16 to 54)
2 (1.1) 3 (1.7) 200 (93)
Electrical Ratings
Motor Ratings VAC 120 208 240 277
AC Full Load A 6.0 3.4 3.0
AC Locked Rotor A 36.0 20.4 18.0
Non-Inductive or Resistance Load A
(Not Lamp Loads)
10.0 9.2 8.0 7.2
Pilot Duty 125 VA, 24 to 277 VAC
A28AK Thermostat
Multi-Stage Electromechanical Temperature Controls
Code No. LIT-1927115
Repair Information
If the A28 Series Two-Stage Flange Mounted
Duct Thermostat fails to operate within its
specifications, replace the unit. For a
replacement thermostat, contact the nearest
Johnson
Controls®
representative.