Installation Sheets Manual 121
Temperature Controls Section
Technical Bulletin A19K, A28K
Issue Date 0119
© 2019 Johnson Controls 1
Code No. LIT-121078
Part No. 996-241, Rev. A
A19K, A28K Series
Industrial Controls
Application
These controls are for
refrigeration, air conditioning
and heating applications.
Control ranges are available to
cover working temperatures
from -30 to 550°F (-35 to
288°C). Controls have NEMA
3R rainproof enclosure for a
broad range of industrial and
general purpose applications.
The A19 single-stage controls
are available with open low,
open high or SPDT contact
action. The A28 two-stage
controls have SPDT contact
action on both switches.
All Series A19K and A28K
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
When the temperature increases
to the control dial setting on the
single-pole, double-throw model,
the circuit between “R” and “Y”
closes. Simultaneously the
circuit between “R” and “B”
opens.
Figure 3 illustrates the two-stage
operation of the A28KA and
A28KJ. On a temperature
increase to the dial setting, the
circuit between “R” and “Y” of
the low stage switch (RYL)
closes. Simultaneously the
circuit between “R” and “B” (RBL)
opens. On a further increase in
temperature the high stage
switch operates and closes RYH
while simultaneously opening
RBH. The reverse sequencing
takes place on a temperature
fall.
Installation
Mounting
Mount the control with the
conduit connector pointing
down. Mount to any flat surface
with screws or bolts through the
rubber bushing in the three
mounting feet. (See Fig. 1.)
CAUTION: Do not dent or
deform the sensitive bulb
(element) of this control. A
dent or deformation will
change the calibration and
cause the control to cycle
at a temperature lower
than the dial setting.
When installing the bulb in a
closed tank, turn off liquid
supply, relieve pressure and
lower liquid level below the
opening before installing or
removing the bulb or bulb well.
For closed tank applications
without well assembly Part
No. FTG13A-600R packing nut
assembly may be supplied. This
packing nut is for applications
where the temperature does not
fall below -35°F (-37°C) or
exceed +250°F (121°C).
Maximum liquid pressure limit is
150 PSIG (1034 kPa). See Fig.
4 for sequence of installation.
Put parts over support tube
section of element, placing bulb
into tank. Tighten 1/2 in. NPT
adapter. Screw packing nut into
adapter with the retaining
washers and packing in place as
shown.
To install models supplied with
bulb well, first install bulb well
into tank. Remove bushing from
bulb well and slide bushing over
capillary. Push bulb into position
in bottom of well. Replace
bushing into bulb well.
Tighten set screw in end of
adapter to hold bulb in position.
See Fig. 5 for bulb well
illustration.
Wiring
WARNING: Disconnect
power supply before
wiring connections are
made to avoid electrical
shock or possible
damage to equipment.
Fig. 1 -- Industrial control with
remote bulb.
