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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-59
A28 Series Two-Stage Temperature Control
Description
The A28 Series are two-stage temperature controls that incorporate a
liquid-filled sensing element.
Refer to the A28 Series Two-Stage Temperature Controls with
NEMA 1 Enclosure Product Bulletin Product Bulletin (LIT-125130) for
important product application information.
Features
• wide temperature ranges available
• constant differential throughout the entire range
• single-pole, double-throw (SPDT) snap-acting switches
• unaffected by changes in barometric pressure
• unaffected by cross ambient conditions
• compact enclosure
• variety of sensing element styles
Action on Increase
of Temperature
Y
B
R
Y
B
R
A28 Series
Low Stage High Stage
A28 Action Diagram
a28.eps
Applications
Use for temperature sensing applications requiring two-stage control of
HVAC/R equipment.
Accessories
• packing nut assembly available for direct immersion applications
(Code No. FTG13A-600R)
• remote bulb models include 5/8 in. mounting clip
Selection Charts
Product Code
Number
Switch
Action
Range
°F (°C)
Differential
F° (C°)
Bulb and
Capillary
Bulb Well No.
(Order Separately)
Range
Adjuster
Coiled Bulb-Fixed Differential
A28AA-4C Two-SPDT 30 to 110
(-1 to 43)
3-1/2 (1.9) each stage
3 (1.7) fixed between stages
1-3/8 in. x 2-1/4 in.
coiled
–Convertible
Case Compensated-Fixed Differential
A28AA-9C Two-SPDT 20 to 80
(-7 to 27)
3-1/2 (1.9) each stage
3 (1.7) fixed between stages
3/8 in. x 5 in.
6 ft capillary
1
1. Packing nut assembly available for direct immersion applications (Code No. FTG13A-600R).
WEL14A-603R Knob
Wide Range-Adjustable Interstage Differential
A28AA-28C Two-SPDT 30 to 110
(-1 to 43)
3-1/2 (1.9) each stage
2 to 7 adjustable between stages
12 ft averaging bulb
6 ft capillary
– Screwdriver
slot
A28AA-29C Two-SPDT -30 to 100
(-34 to 38)
5 (2.8) each stage
2 to 7 adjustable between stages
3/8 in. x 4 in.
8 ft capillary
1
WEL14A-602R Convertible
A28AA-36C Two-SPDT 40 to 90
(4 to 32)
3 each stage
2 to 7 adjustable between stages
3/8 in. x 5-3/4 in.
6 ft capillary
– Knob
A28AA-37C Two-SPDT 60 to 140
(16 to 60)
5 each stage
2 to 7 adjustable between stages
3/8 in. x 4 in.
6 ft capillary
WEL14A-602R Knob
A28AJ-4C Two-SPDT 20 to 80
(-7 to 27)
2 each stage
2 to 7 adjustable between stages
3/16 in. x 22 in.
6 ft capillary
– Knob
Changeover Control
A28AB-1C Two-SPDT
2
2. Switches within 1 F° (0.6 C°) of each other.
20 to 80
(-7 to 27)
3-1/2
(1.9)
3/8 in. x 5 in.
6 ft capillary
WEL14A-603R Screwdriver
slot
A28AA-4
Temperature
Control
A28AB-29
Temperature
Control
Multi-Stage Electromechanical Temperature Controls
Code No. LIT-1927110