Installation Instructions A19BAC, A28AA
Issue Date September 2018
© 2018 Johnson Controls 1
Part No. 996-238, Rev. F
A19BAC, A28AA Single and Two-Stage Space Thermostats
for Farm and General Purpose Applications
Application
The single-stage A19BAC and the
two-stage A28AA thermostats
incorporate single-pole double-
throw (SPDT) switches for
controlling automatic ventilation or
heating in livestock barns, poultry
houses, milk houses, brooder
houses and other buildings. The 30
to 110F (0 to 43C) and 0 to 140F
(-15 to 60C) temperature ranges
permit use for many space
applications.
IMPORTANT: The single stage A19
and A28 thermostat is intended to
provide an input to equipment
under normal operating conditions.
Where failure or malfunction of the
thermostat could lead to personal
injury or property damage to the
controlled equipment or other
property, additional precautions
must be designed into the control
system. Incorporate and maintain
other devices, such as supervisory
or alarm systems or safety or limit
controls, intended to warn of or
protect against failure or
malfunction of the thermostat.
IMPORTANT : Le single stage A19
and A28 thermostat est destiné à
transmettre des données entrantes
à un équipement dans des
conditions normales de
fonctionnement. Lorsqu'une
défaillance ou un
dysfonctionnement thermostat
risque de provoquer des blessures
ou d'endommager l'équipement
contrôlé ou un autre équipement, la
conception du système de contrôle
doit intégrer des dispositifs de
protection supplémentaires. Veiller
dans ce cas à intégrer de façon
permanente d'autres dispositifs,
tels que des systèmes de
supervision ou d'alarme, ou des
dispositifs de sécurité ou de
limitation, ayant une fonction
d'avertissement ou de protection en
cas de défaillance ou de
dysfonctionnement du thermostat.
WARNING: Risk of Property
Damage.
Do not install the A19 or A28
temperature controls with general
purpose enclosures in any type of
agricultural environment defined in
NEC Art. 547 where dust or dust
with water may accumulate or
where corrosive atmospheres exist.
Failure to comply with NEC Art. 547
may cause the A19 or A28 control
to fail and result in the loss of
temperature regulation and
damage to other property.
MISE EN GARDE : Risque de
dégâts matériels.
Ne pas installer les régulateurs de
température A19 or A28 équipés de
boîtiers à usage général dans tout
type d'environnement agricole, tel
que défini dans l'article 547 du
National Electrical Code (NEC, Code
électrique national des États-Unis),
dans lequel ils pourraient être
soumis à l'accumulation de
poussière ou de mélange
poussière/eau, ou à une atmosphère
corrosive. Le non-respect de l'article
547 du NEC risque d'entraîner une
défaillance du régulateur A19 or A28
et de provoquer l'interruption de la
régulation thermique et d'autres
dégâts matériels.
Operation
Figs. 4 and 5 illustrate the
operation of the A19. On a
temperature increase, the circuit
between R and Y closes.
Simultaneously the R and B circuit
opens.
Figure 6 illustrates the operation of
the A28AA. On a temperature
increase, the circuit between R and
Y of the low stage switch (RY
L
)
closes. Simultaneously, the circuit
between R and B (RB
L
) opens.
Fig. 1 -- Exterior view of Space
Thermostat
On a further increase in
temperature, the high stage switch
operates and closes RY
H
while
simultaneously opening RB
H
.
The reverse sequencing takes
place on a temperature fall.
Installation
Mounting
Mount control to a flat surface with
screws through holes provided in
back of frame.
IMPORTANT: On rough mounting
surfaces, use the top two
mounting holes only. When
these controls are mounted
on an uneven surface using
screws in all four holes, the
case can be twisted enough
to affect the thermostat’s
calibration and operation.
Mount the control where it is
exposed to the average
temperature of the controlled
space. Do not mount where it will
be affected by unusual heat or cold,
such as directly over an animal
stall, in sunlight, or on an outside
wall. Avoid locations near a door,
window or hay chute.
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