Installation Sheets Manual 121
Temperature Controls Section
Technical Bulletin A11
Issue
Date
0790
© 1990 Johnson Controls, Inc.
1
Code No. LIT-121010
Part No. 997-358
A11 Series
Low Temperature Cutout Control
Application
A11 Series low temperature
cutout controls are available with
SPDT or SPST contact action.
Typical applications include the
sensing of low temperature
conditions to avoid overcooling
or icing of hydronic coils, cooling
coils and liquid handling pipes.
The controls are compact and
sturdy, and have an adjustable
temperature set point range with
a fixed differential. The range
adjustment screw is accessible
at the bottom of the control, and
at the top of the control when the
cover is removed.
All Series A11 temperature
controls are designed for use
only
as operating controls.
Where an operating control
failure would result in personal
injury and/or loss of property, it is
the responsibility of the installer
to add devices (safety, limit
controls) or systems (alarm,
supervisory systems) that protect
against, or warn of, control
failure.
Operation
The A11D and A11E models
have SPDT contact action;
models A11A and A11B have
SPST contacts. When
16 inches (406 mm) or more of
an A11’s sensing bulb senses a
temperature equal to or lower
than the set point, the contacts
will open on SPST controls, or
the circuit between the Red and
Yellow terminals will open on
SPDT controls. The A11A and
A11D models lock out when the
temperature decreases below
the control’s temperature set
point and must be manually
reset by depressing the trip free
reset lever (which must be
pressed and released before
power will be restored) when the
temperature increases 12F
°
(6.7C
°
) or more above the set
point. The A11B and A11E will
automatically recycle on an
increase in temperature.
Installation
Mounting
The bulb is usually located on
the downstream side of the coil
with the bulb exposed to all
areas where low temperatures
are likely to be encountered.
The sensing element is 20 feet
(6.1 m) long and should be
horizontally serpentined across
the face of the coil to sense
temperatures in all areas. (See
Fig. 2.) Do not install A11 Series
controls where the ambient
temperature at the control
exceeds 140
°
F (60
°
C), or falls
below 0
°
F (-18
°
C). The
maximum temperature at the
sensing bulb should not exceed
250
°
F (121
°
C).
Wiring
!
CAUTION: Disconnect the
power supply before wiring
connections are made to
avoid possible electrical
shock or damage to the
equipment.
Make all wiring connections using
copper conductors only, and in
accordance with the National
Electrical Code and local
regulations. For maximum
electrical rating of the control, see
the cover label on the inside of the
control cover. Loads exceeding
the rating of the control can be
handled with a relay or motor
starter. On the SPDT models the
Red terminal is the common
terminal. See Fig. 3 for terminal
identifications.
Note
: Use terminal screws
furnished (8-32
×
1/4 in. binder
head). Substitution of other
screws may cause problems in
making proper connections.
Fig. 1 -- Interior view of a Low
Temperature Cutout Control with
manual reset.
