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100
80
60
100% CAPACITY AT 4 mA
40
20
0
0
2
TROUBLESHOOTING
Compressor
Protection
(CPCS) Board —
The compressor protection board con-
trols the compressor and compressor crankcase heater.
The ground current protection is provided by the compres-
sor board.
The large relay located on the board is used to provide a
feedback signal to the Main Base Board.
The operation of the compressor board can be checked us-
ing the Service Test procedure. When the Service Test step is
turned on, the compressor board is energized. All safeties are
continuously monitored. The crankcase heater will be turned
off and the compressor contactor will be turned on. The feed-
back contacts will close and the Main Base Board (MBB) will
read the feedback status.
If the board does not perform properly, use standard wiring
troubleshooting procedures to check the wiring for open cir-
cuits. Refer to Alarms and Alerts section on page 48 for alarm
or alert codes for possible causes for failure.
If a compressor short-to-ground exists, the compressor
board may detect the short before the circuit breaker trips. If
this is suspected, check the compressor for short-to-ground
failures with an ohmmeter. The ground current is sensed with a
current toroid (coil) around all 3 or 6 wires between the main
terminal block and the compressor circuit breaker(s).
Compressor Ground Current (CGF) Board
(30GTN,R and 30GUN,R 130-210, 230A-315A,
and 330A/B-420A/B) —
cuit of these units. Each board receives input from up to 4 tor-
oids wired in series, one toroid per compressor. With 24 v sup-
plied at terminals A and B, a current imbalance (compressor
ground current) sensed by any toroid causes the NC (normally
closed) contacts to open, shutting down the lead compressor in
the affected circuit. All other compressors in that circuit shut
down as a result. The NC contacts remain open until the circuit
is reset by momentarily deenergizing the board using the push-
button switch.
If the NC contacts open, it is necessary to remove toroids
from the T1-T2 circuit to determine which toroid is causing the
trip. The chiller circuit can then be put back on line after the
circuit breaker of the faulty compressor is opened. The com-
pressor problem can then be diagnosed by normal trouble-
shooting procedures.
EXV Troubleshooting —
not properly controlling operating suction pressure or super-
heat, there are a number of checks that can be made using
75% CAPACITY AT 12 mA
4
6
8
DEMAND LIMIT SIGNAL – 4 - 20 mA INPUT (VOLTS DC)
Fig. 23 — 4 to 20 mA Demand Limiting
Control
System
One board is used for each cir-
If it appears that the EXV is
50% CAPACITY AT 20 mA
10
12
14
the quick test and initialization features built into the
ComfortLink™ control.
Follow the procedure below to diagnose and correct EXV
problems.
STEP 1 — CHECK PROCESSOR EXV OUTPUTS —
Check EXV output signals at the J6 and J7 terminals of the
EXV board.
Turn unit power off. Connect the positive lead of the meter
to terminal 3 on connector J6 on the EXV board. Set meter for
approximately 20 vdc. Turn unit power on. Enter and enable
the Service Test mode. Locate the appropriate EXV under
'OUTS.' Select the desired percentage and press Enter to move
the valve. The valve will overdrive in both directions when
either 0% or 100% are entered. During this time, connect the
negative test lead to terminals 1, 2, 4, and 5 in succession. The
voltage should fluctuate at each pin. If it remains constant at a
voltage or at 0 v, replace the EXV board. If the outputs are cor-
rect, then check the EXV.
To test Circuit B outputs, follow the same procedure above,
except connect the positive lead of the meter to terminal 3 on
connector J7 on the EXV board and the negative lead to termi-
nals 1, 2, 4, and 5 in succession.
STEP 2 — CHECK EXV WIRING — Check
EXVs from J6 and J7 connectors on EXV board.
1. Check color coding and wire connections. Make sure
that wires are connected to correct terminals at J6 and
J7 connectors and EXV plug connections. Check for
correct wiring at driver board input and output termi-
nals. See Fig. 2-4.
2. Check for continuity and tight connection at all pin
terminals.
3. Check plug connections at J6 and J7 connectors and at
EXVs. Be sure EXV connections are not crossed.
STEP 3 — CHECK RESISTANCE OF EXV MOTOR
WINDINGS — Remove connector at J6 and/or J7 of EXV
board and check resistance between common lead (red wire,
terminal D) and remaining leads A, B, C, and E. Resistance
should be 25 ohms ± 2 ohms. Check all leads to ground for
shorts.
STEP 4 — CHECK THERMISTORS THAT CONTROL
EXV — Check thermistors that control processor output volt-
age pulses to the EXVs. Circuit A thermistor is T7, and circuit
B thermistor is T8. Refer to Fig. 9 and 10 for location.
1. Refer to Thermistors section on page 59 for details on
checking thermistor calibration.
47
16
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20
wiring
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