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NOTE: The control does not detect circuit breaker
failures. If a circuit breaker trips on the lead compressor
in a circuit, a
low
oil
pressure failure will be indicated;
on the other compressors, no failure will be indicated.
Checkout
P~-o~etiur~
(Codes 51-54)
-
Shut off the main
power to the unit. Turn on control power, then step
through the Quick Test to the proper compressor number
(i.e., failure code
S3
is
step
CBT). Next, energize the
step. If the step works correctly, then the failure code
is due to:
. HPS
open
l
Ix-r
open
l
Mj~placcd
fu&
back wire from 2H5 strip to 293 strip
l
Ground wire and 24-volt feeds reversed on one or more
points on
2.t.3.
The 24-volt ground wire (brown)jumps
terminals 2, 4, 6 and 8. Feeds from compressors Al,
A2, Bl and 82 connect to pins I, 3, 5 and 7.
The processor closes the contacts between 255 ter-
minals 12 and
1
I to start the
cc3mprwsor.
(See Fig. 3.) The
safeties shown to the right of 2.15 must be closed for
power to reach the compressor
c<)ntroX
relay (CR 1) and
the feedback input (terminal
t
~I”I
2,13).
Failure of power to terminal
t
OLI
2J3 when contacts
255
1
I and I2 should be
closed
wilt
cause
a code 5
1
alarm.
Terminal 2 on 293 is the other leg
of
the compressor Al
feedback channel. It is connected to the 24-volt ground.
Code 59 and 60, Loss of Refrigerant Charge
~
A loss-of-
charge switch is connected to the high-pressure side of
the refrigerant system. The microprocessor monitors this
switch directly; if it opens, all the compressors in the
circuit will be locked off, the alarm will be energized and
the display code will appear when the alarm display is
accessed. To reset, use the manual reset method (move
the RUN/STANDBY switch to STANDBY, then back
to RUN).
Following are some possible causes for this alarm:
f,n\a>
RejPigerant
Charge
-
If the system refrigerant
charge is very low, the microprocessor will detect this
through the switch and indicate the error.
StzYtch
Failure
-
If the switch f&s open, the micro-
processor will detect this and indicate an error.
Wiring Error
-
If there is a wiring error that causes an
open circuit, the microprocessor
wikk
treat this as an open
switch and indicate an error.
Proc~esssr
Board Failure
-
If the hardware in the pro-
cessor module fails in a manner that the switch cannot
be read properly, an error may be indicated.
Code 61, No Cooler
Flow
-
The microprocessor con-
tains logic that prutects the cooler against loss of cooler
flow.The cooler entering and leaving water temperature
sensors are used for this purpose. The leaving thermistor
is located in the leaving water nozzle and the entering
sensor is located in the first cooler baffle space in close
proximity to the cooler tubes as shown in Fig. 4. When
there is no cooler water flow and the compressors are
operating, the leaving water temperature thermistor will
indicate no temperature change. But the temperature of
the entering water will drop rapidly and the entering
water thermistor will detect this. When the entering water
temperature drops to 5 F (2.8 C) below the leaving water
temperature,
alf
the compressors will stop and code
no. 61 will be displayed. To correct, use manual reset
method (after cooler water Row is resumed).
The error will be caused either by no cooler flow or
if the water is flowing in the wrong direction through the
cooler or if the thermistors have been interchanged.
Fig. 3
-
Compressor Al Control Wiring (Typical)
Code 63 and 64, Low Oil Pressure
~~
A low oil pressure
switch is installed on the lead compressor in each circuit.
If the switch opens during operation of the compressor,
all the compressors in the circuit will be shut off, the alarm
light will be energized and the appropriate display code
shown. The switch will be bypassed for one minute during
start-up and for 45 seconds during normal operation. The
manual reset method must be used to reset this safety.
Possible causes for failure are:
Loss of’ Oil
Pres.sute
-
If the oil pressure is below 5
&
1
psig (34.5
&
6.9 kpa), the switch will open.
.S\i’itch
Failure
-
If the switch fails open, a failure will be
indicated.
Compwssor is
not
running.
wiring
Errur
-
If a wiring error exists that causes an
open circuit, an error will occur.
Pm~essov
Mod&
Faifure
~
If the hardware on the
processor module fails in a manner that the switch cannot
be read properly, an error may be indicated.
Code 65, Cooler Freeze Protection ~ If the leaving water
temperature is below 35 F (1.7 C) for a water chiller or
is 6’F (3.3 C)
below
the set point for brine applications,
all compressors wiil be stopped. This safety will auto-
matically reset when the water temperature is 6 F (3.3 C)
above the set point.
The causes for this failure are usually due to low cooler
flow, or extremely rapid load changes.
Code 66 and 67, High Suction Superheat
-
The micro-
processor contains the following logrc and
ifit
is satisfied,
all the compressors in the circuit will be stopped:
Suction superheat is greater than 75 F (4f.7 C), and
saturated cooler suction is
iess
than 55 F (12.8 C) and
these 2 conditions have been true for more than5 minutes.
To reset this, use the manual reset method.
Causes for this failure are:
IL);%’
R<fkigeranf
C’hwge
~
A low refrigerant charge
will.
not allow the correct amount of refrigerant to be fed to
the evaporator, which will result in a high superheat.
Pbuggcd
Filter Drier
-
If the liquid line filter drier
becomes plugged, it can result in not enough refrigerant
being fed to the evaporator, which results in a high super-
heat failure.
EXY Failure
-
If the EXV fails to open enough to feed
the proper amount of refrigerant, the error will occur.
EXV
Dviveu
Moduk Failure
~
Xf
the DSIO module
hardware that controls the EXVs fails, the
valve
will
not move.
13