Johnson Controls System 350 A350A Service manual

FANs 930, 930.5, 125, 121
Product/Technical Bulletin A350
Issue Date 0899
© 1999 Johnson Controls, Inc. 1
Part No. 24-7664-44, Rev. C www.johnsoncontrols.com
Code No. LIT-930010
The A350A/B Series is an on/off electronic
temperature control with a Single-Pole, Double-Throw
(SPDT) relay output and a Light-Emitting Diode (LED)
relay status indicator. Designed to operate with both
heating and cooling equipment, this control includes an
adjustable differential and an interchangeable
temperature sensor.
As are all System 350™ products, the A350A/B is
housed in a NEMA 1, high-impact plastic enclosure.
The modular design provides easy, plug-together
connections for quick installation and future
expandability.
Figure 1: A350 Series Electronic
Temperature Control
Features and Benefits
❑Modular Design Enables stage, display, and power modules to
be purchased and installed as needed
❑
❑❑
❑Plug-together Connectors
and 35 mm DIN Rail
Mounting
Eliminates wiring between modules and
reduces installation costs
❑Two Standard Models
Cover Wide Setpoint
Ranges
-30 to 130°F (-34 to 55°C) or
90 to 250°F (32 to 121°C)
Reduces inventory by encompassing
temperature ranges required to support the
majority of Heating, Ventilation, Air
Conditioning, and Refrigeration (HVAC/R)
applications
❑Wide Adjustable Differential
of 1 to 30F° (0.6 to 16.7C°)
Enables the user to match equipment cycle
rate and/or sequencing for a given application
❑
❑❑
❑Field-Selectable Mode
Jumpers
Operates in both heating and cooling
applications
❑
❑❑
❑Available with Either
External or Concealed
Setpoint
Helps deter accidental and unauthorized
adjustments
❑
❑❑
❑Interchangeable
Temperature Sensors
Increases versatility and serviceability
System 350™
A350A/B Electronic Temperature Control

2 System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin
Application
The A350A/B Temperature Control can be used as
a standalone device or in conjunction with other
System 350 plug-together modules to control single or
multiple-stage HVAC or refrigeration equipment.
Typical applications include:
•frozen/refrigerated food cases
•cooling tower control
•beverage/milk coolers
•chiller staging
•space temperature control
A typical System 350 Temperature Control
arrangement includes the following:
•A350A/B Temperature Control
•S350 Stage Modules
•D350 Digital Temperature Sensor/Setpoint Display
Module
•Y350R Power Module (or Class 2
24 VAC transformer)
•A99B Series Temperature Sensor
Operation
The A350A/B Temperature Control operates on
24 VAC and provides an SPDT relay output. A front
panel LED lights to indicate when the relay is
energized. Adjustable features include:
•setpoint
•differential
•heating/cooling mode
IMPORTANT: All System 350 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) that
protect against, or systems
(alarm, supervisory systems) that
warn of, control failure.
Setpoint Adjustment
Setpoint is defined as the temperature at which the
A350A/B’s relay de-energizes. Use the Setpoint Dial on
the front of the A350A/B to adjust setpoint. See
Figure 2.
Differential Adjustment
Differential is defined as the change in sensor
temperature between energization and de-energization
of the relay. Adjustment of the A350A/B differential is
made using the potentiometer marked DIFF. See
Figure 2 for its location. Refer to Table 5 for
adjustment ranges.
Relay
Module
Connector
Relay
LED Indicator
Setpoint
Dial
DIFF
(Differential
Potentiometer) Jumper Block
Position
Heating
Cooling
24V
COM
VDC
SEN
NC NO
Figure 2: A350A/B Board Layout and
Terminal Locations
Heating/Cooling Mode Adjustment
With Heating mode selected, the differential is below
setpoint. The relay and LED indicator will de-energize
as the temperature rises to the setpoint. As the
temperature drops to the setpoint minus the differential
setting, the relay will energize and the LED illuminates.
Refer to Figure 6.
With Cooling mode selected, the differential is above
setpoint. The relay and LED indicator will de-energize
as the temperature drops to setpoint. As the
temperature rises to the setpoint plus differential
setting, the relay will energize and the LED illuminates.
As shipped from the factory, the heating/cooling
jumper blocks are installed in the horizontal (cooling)
position. See Figure 2.

System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin 3
Add-On Modules
The S350 Stage Modules, D350 Digital Temperature
Display Module, and Y350R Power Module connect
together and plug into the A350 via a connector on its
right side. The maximum number of add-on modules is
listed in Table 1.
Table 1: Maximum Number of S350 Stage
Modules per A350A/A350B
Power
Source
Number
of S350A
or S350C
Modules
Allowed
Number
of S350A
or S350C
Modules
(with
1 S350P)
Allowed
Number of
S350A or
S350C
Modules
(with
2 S350P)
Allowed
Y350R 96 4
External
Class 2
Transformer
98 7
Note: For each S350P added, the number of S350A
or S350C Stage Modules that can be used
with a Y350R decreases by two. If an external
transformer is used, the number of S350A and
S350C Stage Modules used decreases by
one for each additional S350P.
S350A On-Off Stage Modules
S350A On-Off Stage Modules receive power, setpoint,
and sensor input from the A350 control. S350A Stage
Modules perform switching functions based upon the
A350’s setpoint and sensor information, with the offset
and differential selected at the S350A.
For more information on these modules, refer to the
System 350 S350 Temperature, S351 Humidity, and
S352 Pressure On/Off Stage Modules
Product/Technical Bulletin (LIT-930080).
S350C Slave Stage Modules
S350C Slave Stage Modules receive power and
sensor input from the A350 control. S350C Slave
Stage Modules perform switching functions based
upon the A350’s sensor information. (Setpoint and
differential are selected independently at the S350C.)
For more information on these modules, refer to the
System 350TM S350C Temperature Slave Stage
Module Product/Technical Bulletin (LIT-930084).
S350P Proportional Stage Modules
S350P Proportional Stage Modules receive power,
setpoint, and sensor input from the A350 control.
The S350P responds with an analog 0-10 VDC and
0-20 mA output signal. This is based upon the A350’s
setpoint and sensor information, with the offset,
throttling range, and minimum output selected at the
S350P.
For more information on these modules, refer to the
System 350TM S350P Proportional Plus Integral
Temperature Stage Module Product/Technical Bulletin
(LIT-930086).
D350 Temperature Sensor/Setpoint
Display Module
The D350 receives power, sensor, and setpoint
information from the A350. A 3-digit Liquid Crystal
Diode (LCD) gives continuous read-out of the sensed
temperature. Pushing the PRESS FOR SETPOINT
button on the front of the D350 causes the setpoint of
the adjoining A350 to be displayed.
Y350R Power Module
The Y350R provides a convenient method of powering
System 350 modules from a 120 or 240 VAC power
source. The Y350R supplies power to the modules.
See Figure 5 for a typical wiring diagram where a
Y350R is used to power the A350.
For more information on this module, refer to
System 350TM Y350R Power Module
Product/Technical Bulletin (LIT-930090).

4 System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin
Dimensions
Mounting Slots
for No. 6 Screws
DIN Rail
Mount
Conduit
Hole
(75)
3/16 (4)
1/2 (13)
2 15/16
1 9/16
(40)
2 3/8 (61)
1 3/16 (31)
7/8
(22)
7/16 (11)
9 3/4 (248)
Sensor
1/4 (6)
7/8
(22)
3 (76)
2 3/8 (61)
5 (127)
4 (102)
Figure 3: A350A/B Control Dimensions, in. (mm)
Installation and Wiring
The A350A/B Temperature Control is housed in a
compact NEMA 1 plastic enclosure designed for
standard 35 mm DIN rail mounting. The A350A/B is not
position sensitive but should be mounted for convenient
wiring and adjustment. Four key-slot mounting holes on
the back of the control case are provided for surface
mounting. Add-on modules must plug into the right side
of the A350A/B control.
Note: When mounting the System 350 modules to rigid
conduit, attach the hub to the conduit before
securing the hub to the control enclosure.
!
WARNING: Risk of Electrical Shock.
Disconnect power supply before
wiring connections are made to
avoid electrical shock or damage
to equipment.
•All wiring must conform to the National Electrical
Code and/or local regulations.
Note: For maximum electrical rating of control, see
label inside the control cover or Specifications
section. Use copper conductors only.
•Consult the typical wiring diagrams (Figures 4 and 5)
for proper wiring and terminal designations.
A350A/B D350 S350A
Sensor
Load Load
L
L24
VAC
1
1
2
2
24V
COM
VDC
SEN
Note: If sensor is mounted less than 50 ft
(15.2 m) from the A350A/B,
shielded cable is not required.
Figure 4: Typical Wiring Diagram for A350A/B
Powered by an External 10 VA Transformer

System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin 5
Sensor Connection
Shielded cable is not generally required for sensor
wiring on runs of less than 50 ft (15.2 m), but is
recommended for lengths greater than 50 ft (15.2 m).
When using shielded cable, isolate and tape the shield
at the sensor. Connect the shield to the COM sensor
terminal on the A350A/B. (See Figure 2 for terminal
location.) The A99BA-200C sensor, which includes
shielded cable, is available if needed.
Note: At the maximum cable lengths listed in Table 2,
no more than 1F° (0.6C°) error in the sensed
temperature will result due to wire resistance.
Table 2: Recommended Maximum Sensor
Cable Lengths
Wire Shielded Cable Length*
Gauge Feet Meters
14 AWG 800 244
16 AWG 500 152
18 AWG 310 94
20 AWG 200 61
22 AWG 124 38
* Values provided are for 2-wire stranded cable.
•Various A99B Series Temperature Sensors and
mounting hardware are available for use with A350
Series Controls. See Tables 3 and 6. The sensor
must be connected to the COM and SEN terminals
on the four-position terminal strip located at the top
left of the printed circuit board (Refer to Figures 2,
4, and 5.). The sensors are not polarity sensitive.
•The sensor must be mounted so that it can
accurately sense the temperature of the controlled
medium.
Table 3: Sensors Included With A350A/B
Controls
Control Sensor Included
Sensor lead length is 9-3/4 in. (0.25 m)
A350AA-1C A99BB-25C; Range: -40 to 212°F
(-40 to 100°C)
A350AA-2C A99BC-25C; Range: -40 to 248°F
(-40 to 120°C)
A350AA-3C A99BB-25C; Range: -40 to 212°F
(-40 to 100°C)
A350AB-1C No Sensor Included
A350AB-2C No Sensor Included
A350AB-5C No Sensor Included
A350BA-1C A99BB-25C; Range: -40 to 212°F
(-40 to 100°C)
A350BA-2C A99BC-25; Range: -40 to 248°F
(-40 to 120°C)
A350BB-1C No Sensor Included
•For more information regarding sensor options and
installation, refer to the A99B Series Temperature
Sensors Product/Technical Bulletin (LIT-125186).
A350A/B S350A S350A D350S350A
Load Load Load Load
Y350R
120 VAC
Shield (Connect
to COM on A350)
Sensor
Figure 5: System 350 Powered by Y350R Module

6 System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin
Adjustments
Follow this procedure to set up the A350A/B for the
desired operation.
1. Remove the A350 cover by loosening the
four captive cover screws.
2. Set the heating/cooling jumper blocks to the
desired mode of operation. Position the jumper
blocks vertically for heating or horizontally for
cooling. (See Figure 2.)
IMPORTANT: Verify that the heating/cooling
jumper blocks are in the proper
position before powering the
System 350 modules. If the
jumper blocks on the control or
staging modules are installed in
the wrong position, the device will
activate the relay in response to
the opposite signal. The heating
or cooling equipment will remain
energized until the error is
corrected.
3. Adjust the differential potentiometer (DIFF) on the
A350 as needed. (Figure 6 is an example of a
multistage application.) The stage module’s offset
and differential can be set independently.
ON
OFF
Differential
ON
OFF
S350A
Stage 2
A350
Stage 1
Setpoint
Temperature
(+)
(-)
Differential
ON
OFF
Differential
ON
OFF
S350A
Stage 4
S350A
Stage 3
Differential
ON
OFF
Differential
ON = Energized
OFF= De-energized
Stage 5
S350A
HeatingCooling
Jumper Set To
OFFSET
OFFSET
OFFSET
OFFSET
Figure 6: Typical Multistage
Heating/Cooling Application
4. Replace the cover, and secure in place with the
four captive screws. Move the setpoint dial to the
desired position.
Note: The A350A/B setpoint is factory calibrated at
midscale to a tolerance of +/- 1F° (0.6C°).
Setpoint tolerance at the extreme ends of the
setpoint ranges in relation to the printed scale
can be +/- 3F° (1.7C°). The D350 Display
Module is unaffected by this tolerance shift.
Use the D350 for the most accurate setpoint
selection.
Checkout Procedure
Follow this procedure to verify that the A350A/B is
connected and functioning properly.
1. Make sure installation and wiring connections are
according to job specifications before applying
power. (Refer to Figure 6 for an example of a
multistage application.)
2. Make the necessary adjustments and electrical
connections.
3. Put the system in operation and observe at least
three complete operating cycles before leaving the
installation.
Troubleshooting
If the control system does not function properly, verify
that the proper mode is selected on each module
(Heat/Cool, Direct Acting/Reverse Acting). Proceed as
follows to determine the cause of the problem:
1. Make sure proper voltage is applied to the A350
control.
a. Connect a digital voltmeter (DVM) between
the 24V and COM terminals located on the
control’s left side terminal block (See Figure 2.)
If an external transformer is used, select AC
volts on the DVM and verify that the voltage is
between 20 and 30 VAC.
If a Y350R Power Module is used, select DC
volts on the DVM and verify that the voltage is
between 16 and 38 VDC.
b. If the DVM reading is within the indicated
voltage range, proceed to Step 2.
c. If the DVM reading is not within the indicated
voltage range, correct the wiring, replace the
Y350R, or replace the external transformer.

System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin 7
2. Check temperature sensor for proper resistance.
a. Take an accurate, independent temperature
reading at the sensor location.
b. Disconnect the sensor from the control. Using
an ohmmeter, measure the resistance across
the two sensor leads. Consult Figure 7 to verify
sensor conformance.
°F Tempera ture
260
240
220
200
180
160
140
120
100
80
60
40
20
0
-20
-40
500 700 900 1100
Resistance (Ohms)
1300 1500 1700 1900 2100
°C
120
100
80
60
40
20
0
-20
-40
Figure 7: Temperature vs. Resistance
Chart for the A99B Series Sensor
c. If the resistance varies substantially from the
optimal resistance for that temperature, the
sensor or wiring must be replaced.
Note: The sensor reading indicated by the D350 may
differ from thermometer readings due to sensor
tolerances, time constants, accuracy of
thermometer, and other factors.
3. Check the A350 for proper operation.
Note: Steps 1 and 2 must be performed first.
a. Adjust the setpoint dial to at least 40°F (22°C)
below the sensor temperature determined in
Step 2.
b. Increase setpoint by slowly turning the dial until
the control relay and LED turn On and Off.
c. If the relay does not perform as indicated in
Table 4, replace the A350.
Table 4: A350 Relay Troubleshooting
Action LED N.O. Contact
Status
Setpoint
Dial Setting*
Heating On Closed (Ts) = Sp - Diff
Heating Off Open (Ts) = Sp
Cooling On Closed (Ts) = Sp + Diff
Cooling Off Open (Ts) = Sp
*(Ts) is sensed temperature, and (Sp) is setpoint
temperature.
Repairs and Replacement
Do not make field repairs or perform calibration.
Replacement controls and A99B Temperature Sensors
are available through the nearest Johnson Controls
representative. See Tables 5 and 6 for ordering
information.
Ordering
Table 5: System 350 Products
Item Product Code
Number
Description
A350 Temperature Controls
(With Temperature Sensors)
A350AA-1C
A350AA-2C
A350AA-3C
A350BA-1C
A350BA-2C
Range: -30 to 130°F; Adjustable Differential: 1 to 30F°
Range: 90 to 250°F; Adjustable Differential: 1 to 30F°
Range: -30 to 130°F; Adjustable Differential: 1 to 30F° (concealed setpoint)
Range: -35 to 55°C; Adjustable Differential: 0.5 to 17C°
Range: 30 to 120°C; Adjustable Differential: 0.5 to 17C°
A350 Controls Without
Sensors
A350AB-5C
A350AB-1C
A350AB-2C
A350BB-1C
Range: 90 to 150°F; Adjustable Differential: 1 to 30F°
Range: -30 to 130°F; Adjustable Differential: 1 to 30F°
Range: 90 to 250°F; Adjustable Differential: 1 to 30F°
Range: -30 to 130°F; Adjustable Differential: 1 to 30F°
Digital Temperature Setpoint
Display Modules
D350AA-1C
D350BA-1C
Fahrenheit Scale
Celsius Scale
On/Off Stage Modules S350AA-1C
S350AB-1C
Fahrenheit Scale
Celsius Scale
Slave Stage Modules S350CC-1C Dual Scale (°F and °C)
Proportional Stage Modules S350PQ-1C Dual Scale (°F and °C)
Power Module Y350R-1C 120/240 VAC, 50/60 Hz Input; Rectified Class 2, 24 VAC Output

8 System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin
Table 6: System 350 Accessories
Item Product Code
Number
Description
Enclosure BOX10A-600R Outdoor PVC sensor enclosure; includes wire nuts
Wall Mount Plate TE-6001-4 Includes sensor mounting clip
Cover T-4000-2644 For wall mount plate
Mounting Clip A99-CLP-1 Surface mounting clip for the A99B Temperature Sensor
Duct Mounting TE-6001-1 Duct-mounting hardware with handy box for A99B sensor
Duct Mounting TE-6001011 Duct-mounting hardware without handy box for A99B sensor
Conduit Adaptor ADP11A-600R 1/2 in. Snap-fit EMT conduit adaptor (box of 10)
Immersion Well WEL11A-601R For liquid sensing applications
Sun Shield SHL10A-603R For use with outside sensors in sunny locations
DIN Rail Sections BKT287-1R
BKT287-2R
12 in. (0.3 m) long
39-1/3 in.(1.0 m) long
DIN Rail End Clamp PLT344-1R Consists of two end clamps
Cables for Remote Mounting
of D350 Display Module
WHA29A-600R
WHA29A-603R
WHA29A-604R
3 ft (0.9 m) This can also be used to daisy chain S350 Stage Modules together.
25 ft (7.6 m)
50 ft (15.2 m)
Specifications
Product A350A/B Electronic Temperature Control
Supply Voltage Y350R Power Module: Input: 120/240 VAC 50/60 Hz
Output: 24 VDC, unfiltered, 10 VA, Class 2
External Source: 24 VAC, 50/60 Hz Class 2 (20-30 VAC)
Note: Only one supply voltage source may be used.
Power Consumption 1.4 VA
Ambient Temperatures Operating: -30 to 150°F (-34 to 66°C)
Shipping: -40 to 185°F (-40 to 85°C)
Humidity 0 to 95% RH non-condensing; maximum dew point: 85°F (29°C)
Setpoint Adjustment Range See Table 5.
Differential Adjustment Range See Table 5.
SPDT Relay Output 120V 208 to 240V
Horsepower: 1/2 1/2
Full Load: 9.8A 4.9A
Locked Rotor: 58.8A 29.4A
Non-Inductive: 10A at 24 to 240 VAC
Pilot Duty: 125 VA at 24 to 240 VAC
Sensor Replaceable positive temperature coefficient sensor
Reference resistance: 1035 ohms at 77°F (25°C)
Material Case and cover: NEMA 1 high-impact thermoplastic
Agency Listings UL Listed, CCN XAPX, File E27734
UL Listed for Canada, CCN XAPX7, File E27734
The performance specifications are nominal and conform to acceptable industry standards. For application at conditions beyond these
specifications, consult Johnson Controls Application Engineering at [phone]. Johnson Controls, Inc. shall not be liable for damages
resulting from misapplication or misuse of its products.
Controls Group
507 E. Michigan Street
P.O. Box 423 Printed in U.S.A.
Milwaukee, WI 53201 www.johnsoncontrols.com