Product Overview

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. © 2009 Johnson Controls, Inc.
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A28 Series
Two Stage Temperature Control
Code No. LIT-1927110
Issued February 1, 2009
Description
The A28 Series are two stage temperature controls that incorporate a
liquid filled sensing element.
Features
• wide temperature ranges available
• constant differential throughout the entire range
• 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/Refrigeration equipment.
Accessories
• packing nut assembly available for direct immersion applications
(Part No. FTG13A-600R)
• remote bulb models include 5/8 in. mounting clip
Selection Charts
Code
Number
Switch
Action
Range
°F (°C)
Diff
F° (C°)
Bulb and
Capillary
Bulb Well No.
(order separately)
Range
Adjuster
COILED BULB–FIXED DIFFERENTIAL
A28AA-4C 2-SPDT 30 to 110
(-1 to 43)
3 1/2 (1.9) Ea. Stage
3 (1.7) Fixed Between Stages
1-3/8 in. x 2-1/4 in.
Coiled
–Convertible
CASE COMPENSATED–FIXED DIFFERENTIAL
A28AA-9C 2-SPDT 20 to 80
(-7 to 27)
3 1/2 (1.9) Ea. Stage
3 (1.7) Fixed Between Stages
3/8 in. x 5 in.
6 ft Cap.
1
1. Packing nut assembly available for direct immersion applications (Part No. FTG13A-600R).
WEL14A-603R Knob
WIDE RANGE–ADJUSTABLE INTERSTAGE DIFFERENTIAL
A28AA-28C 2-SPDT 30 to 110
(-1 to 43)
3 1/2 (1.9) Ea. Stage
2 to 7 Adj. Between Stages
12 ft averaging bulb
6 ft Cap.
– Screwdriver
Slot
A28AA-29C 2-SPDT -30 to 100
(-34 to 38)
5 (2.8) Ea. Stage
2 to 7 Adj. Between Stages
3/8 in. x 4 in.
8 ft Cap.
1
WEL14A-602R Convertible
A28AA-36C 2-SPDT 40 to 90
(4 to 32)
3 Ea. Stage
2 to 7 Adj. Between Stages
3/8 in. x 5-3/4 in.
6 ft Cap.
– Knob
A28AA-37C 2-SPDT 60 to 140
(16 to 60)
5 Ea. Stage
2 to 7 Adj. Between Stages
3/8 in. x 4 in.
6 ft Cap.
WEL14A-602R Knob
A28AJ-4C 2-SPDT 20 to 80
(-7 to 27)
2 Ea. Stage
2 to 7 Adj. Between Stages
3/16 in. x 22 in.
6 ft Cap.
– Knob
CHANGEOVER CONTROL
A28AB-1C 2-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 Cap.
WEL14A-603R Screwdriver
Slot
A28AB-2C
3
3. Maximum sensing element temperature is 250°F (121°C).
2-SPDT
4
4. Switches within 1.5 F° (0.9 C°) of each other.
60 to 90
(16 to 32)
5
(2.8)
Strap-on Grid Bulb
42 in. Cap.
– Screwdriver
Slot
A28AA-4
A28AB-29