6
−
19
T
−
318
4. If no change in suction pressure is detected, check
for resistance (refer to step 6.20.1), and check con-
nections for proper continuity and retest. If the valve
is functioning, and all connections and motor resist-
ance are good, check the drive module (refer to step
5. If the valve is determined to be faulty after complet-
ing the above steps, perform a low side pump down.
Remove valve powerhead assembly, and replace
with a NEW valve powerhead assembly, torque nut
to 35ft-lb, evacuate low
side, and open all service
valves.
CAUTION
DO NOT disassemble piston from NEW suc-
tion modulating valve powerhead assem-
bly. Doing so may result in damage to pis-
ton.
6.20.2 Checking the Controller
a. Turn unit OFF.
b. With voltmeter set to read 20 volts DC, attach the pos-
itive lead to MC1 of the 4-pin connector and the neg-
ative lead to the TP9. Turn ON unit and watch the volt
meter. After a short delay, the reading should remain
unchanged at 0 volts. If 5VDC, make sure the jumper
wire from MC1 to MC8 is in place; if not, install and
retest.
6.20.3 SMV Emergency Repair Procedure
In the event of an SMV failure, and replacement
components are not readily available, the system can be
bypassed by removing the SMV valve piston. To remove
the piston, do the following:
a. Perform a low side pump down (refer to paragraph
b. Remove SMV powerhead by loosening the 2-1/8 inch
diameter nut (see Figure 6-23) to relieve any pres-
sure and then sliding the powerhead out.
c. Remove the piston by loosening the Allen screw and
removing the piston and screw.
d. Install the powerhead assembly (without the piston)
and torque to 35 to 40ft-lbs.
e. Open all valves.
f. Start the unit.
g. Adjust the suction service valve so that the approxim-
ate temperature OR current limit is maintained. For
perishable loads, it is recommended that the adjust-
ment be made so that the available capacity is slightly
larger than the load. The unit will cycle OFF and ON.
h. Once repair parts become available, repair as re-
quired.
6.21 DPRV CHECK PROCEDURE
The discharge pressure regulating valve (DPRV) is
designed to maintain a minimal level of discharge
pressure within the compressor. Refer to paragraph 2.2
for valve setting.
The following procedure can be used to perform a
functional check:
a. Install a high pressure gauge at the discharge service
valve.
b. Install another high pressure gauge at the liquid line
service valve.
c. Run unit with -18
°
C (0
°
F) set point.
d. After five minutes, read both gauges and subtract the
liquid line pressure from the discharge pressure. This
is the actual differential pressure.
e. Using the ambient temperature and the chart below,
determine the replacement differential pressure.
0
10
20
30
40
50
60
70
30
40
50
60
70
80
90
100
110
120
Ambient Temperature (F)
Replacement Differential
Pressure
(psi)
REPLACE DPRV
DO NOT REPLACE DPRV
Figure 6-24 DPRV Replacement Value Chart
NOTE
1. This test should not be run below -1.1
°
C
(30
°
F) or above 49
°
C (120
°
F). If the actual
differential pressure is close to the
replacement differential pressure, it is
recommended that the readings be taken
several times at two minutes intervals.
2. If valve cap is found to be leaking it may be
replaced using cap & O-ring (Carrier P/N
40-50024-00).
6.22 AUTOTRANSFORMER
If the unit does not start, check the following:
a. Make sure the 460VAC (yellow) power cable is
plugged into the receptacle (item 3, Figure 4-1) and
locked in place.
b. Make sure circuit breakers CB-1 and CB-2 are in the
“ON” position. If the circuit breakers do not hold in,
check voltage supply.
c. There is no internal protector for this transformer de-
sign; therefore, no checking of the internal protector is
required.
d. Using a voltmeter and with the primary supply circuit
ON, check the primary (input) voltage (460VAC).
Next, check the secondary (output) voltage
(230VAC). The transformer is defective if output volt-
age is not available.