Troubleshooting - Johnson Controls System 350 A350A Technical Bulletin

A
djustments
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
Setpoint
Temperature
OFF
ON = Energized
OFF= De-energized
(-)
A350 S350A
Stage 1 Stage 2
Cooling
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.
6
System 350 A350A/B Electronic Temperature Control Product/Technical Bulletin
ON
OFF
OFFSET
OFFSET
OFF
OFFSET
OFF
ON
OFF
ON
S350A S350A S350A
Stage 3 Stage 4 Stage 5
Heating
Jumper Set To
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.
C
heckout P
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.
T
roubleshooting
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.)
OFFSET
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
ON
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.
rocedure