Johnson Controls A99B Series Catalog Page
FANs 125, 121, 930, 930.5
Product/Technical Bulletin A99
Issue Date 0615
A99B Series Temperature Sensors
The A99B Series Temperature Sensors are passive
PTC (Positive Temperature Coefficient) sensors.
The A99B sensors are splashproof and are
designed to measure temperature in a variety of
refrigeration applications. Several accessories allow
easy tailoring of the temperature sensor to various
mounting configurations.
Applications include temperature sensing for
freezers and coolers, as well as in defrost
termination sensing, space and return air
temperature sensing, and condenser fan cycling.
Figure 1: A99B Temperature Sensors
Features and Benefits
Variety of Lead Lengths Encompasses most application requirements
and simplifies wiring sensors
Assortment of Mounting
Hardware Available
Very Accurate Sensing
Element
Stainless Steel Sensor Bulb Allows use in more applications than other
Provides configuration for many
applications—customizable
Provides excellent performance in a wide
variety of control applications
types of bulbs; no corrosion
© 2015 Johnson Controls, Inc. 1
Part No. 24-7664-1636, Rev. A www.johnsoncontrols.com
Code No. LIT-125186
pplication Overview
A
IMPORTANT: All A99B Series Sensors are
designed for use only with
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)
that protect against, or warn of,
control failure.
The A99B temperature sensor line offers an
economical solution for a wide variety of
temperature sensing needs in refrigeration and
HVAC applications. Typical temperature sensing
applications and environments include:
Sensor
Sensor
Sensor
Sensor
To Controller
Figure 2: 4-Sensor Averaging Wiring
SensorSensorSensor
freezers
display cases
walk-in coolers
reach-in coolers
defrost termination temperature sensing
condenser fan cycling
space and return air temperature sensing
outdoor air sensing
process cooling and heating
ensor Temperature Averaging
S
Multiple sensors may be wired in a series parallel
arrangement to provide an average temperature
reading in an area when one sensor cannot provide
a representative temperature reading. This can be
accomplished with 4, 9, 16, etc., (2
2
, 32, 42, etc.)
sensors.
In a series parallel arrangement, there must always
be the same number of parallel-connected sensors
as there are series connected sensors.
In Figures 2-4, each parallel leg is represented as a
column of sensors and each series leg as a row of
sensors.
Sensor Sensor Sensor
SensorSensorSensor
To Controller
Figure 3: 9-Sensor Averaging Wiring
Sensor
Senso
Sensor
Sensor
Sensor
Senso
r
Sensor
Sensor
Sensor
Senso
r
Sensor
Sensor
Sensor
Senso
r
r
Sensor
Sensor
2 A99B Series Temperature Sensors Product/Technical Bulletin
To Controller
Figure 4: 16-Sensor Averaging Wiring
imensions
D
1/4 (6)
2 (50)
Figure 5: A99B Sensor, in. (mm)
Accessories
A99B series accessories include the following:
1 1 1/16
9 1/8
(229)
4 5/16
(110)
1/4 (6)
Surface M ount Clip
1/2
(13)
(25.4)
A99-CLP-1
Sun Shield
SHL10A-603R
ADP11A-600R
(25.4)
1
EMT
Conduit
Adapter
1
1 3/4
(44)
4 3/4
(119)
7/8
(23)
Figure 6: Available Accessories, in. (mm)
(42)
4 1/2
(113.5)
PVC Enclosure
BOX10A-600R
3
(76)
1 3/8
(35)
Dia.
3/8
(9.3)
peration
O
The A99B sensor incorporates a PTC silicon sensing
element whose resistance increases with an increase in
temperature. The sensor has a reference resistance of
1,035 ohms at 77F (25C). Each element is calibrated
according to a standard graph, as shown in Table 2.
The A99B series sensors are typically used with
Johnson Controls/PENN System 450™ controls,
MR Defrost controls, MS Multi-Stage controls, and
A421 Electronic Temperature Controls.
The A99B sensors can also be used with
Johnson Controls System 27 NOVA; A255 fan speed
control modules; and R78, DX-9100, XP-9102, XPA-4x1,
System 350™ controls, A419 Electronic Temperature
controls, and XPA-8x1 products.
ounting
M
Mounting Considerations
The A99B sensor may be mounted in virtually any
position. To ensure proper operation of the A99B Series
sensors, observe the following guidelines:
Mount sensors in areas where they are exposed to
representative temperature conditions and sufficient
air mixing. Avoid mounting the sensors where air
stratification exists.
Avoid areas subject to excessive mechanical
vibration or electrical noise.
For outdoor applications, avoid areas where the
sensor will be exposed to direct sunlight because
this causes the sensor to read a higher temperature.
The north side of the building is preferred for outdoor
sensors. If not possible, install a sun shield.
Use a thermally conductive paste where appropriate
to improve the thermal contact with the sensor.
Do not subject silicon cable (A99BC) to any
silicon-based fluids, as this will degrade the cable.
A99B Series Temperature Sensors Product/Technical Bulletin 3
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