53
INSPECTING/OPENING ELECTRONIC EXPANSION
VALVES
To check the physical operation of an EXV, the following
steps must be performed:
1. Close the liquid line service valve of the circuit to be
checked. Put the LOR switch in the OFF position. Using the
HSIO, enter the manual service mode by pressing
.
Enable the mode by pressing
. Switch the LOR
switch to the Local position. Scroll down to the desired
compressor and press
to turn it on. Let compressor
run until gage on suction pressure port reads between 5 and
10 psig. Press
to turn the compressor off. Immedi-
ately after the compressor shuts off, close the discharge
valve.
2. Remove any remaining refrigerant from the system low side
using proper reclaiming techniques. Drain oil from cooler
using Schrader port in cooler inlet line. Turn off the line
voltage power supply to the compressors and control circuit
power.
3. Remove screws holding top cover of EXV. Carefully
remove the top cover from the EXV making sure EXV plug
is still connected.
4. Enter the appropriate EXV test step for EXV-A or EXV-B
by pressing
on the HSIO. Scroll down to display
the desired EXV. Press
and
to initiate the test.
Observe the operation of the valve motor and lead screw.
The motor should turn counterclockwise, and the lead screw
should move up out of the motor hub until the valve is fully
open. Lead screw movement should be smooth and uniform
from fully closed to fully open position. Press
as
needed to reach 100% open. Wait 30 seconds in between
each step for motor to stop moving. Press
to check
open to closed operation. If the valve is properly connected
to the processor and receiving correct signals, yet does not
operate as described above, the valve should be replaced.
INSPECTING/OPENING ECONOMIZERS — To check the
physical operation of an economizer (see Fig. 13), the follow-
ing steps must be performed:
1. Close the liquid line service valve of the circuit to be
checked. Put the LOR switch in the OFF position. Using the
HSIO, enter the manual service mode by pressing
.
Enable the mode by pressing
. Switch the LOR
switch to the Local position. Scroll down to the desired
compressor and press
to turn it on. Let compressor
run until gage on suction pressure port reads between 5 and
10 psig (34.5 and 69.0 kPa). Press
to turn the com-
pressor off. Immediately after the compressor shuts off,
close the discharge valve and the bubbler valve on 30HX
units (located in elbow fitting on condenser shell). For
30GX units, there is no shutoff valve in the bubbler tube
line.
2. Remove any remaining refrigerant from the system low side
and discharge piping using proper reclaiming techniques.
Drain oil from cooler using Schrader port in cooler inlet line.
Turn off the line voltage power supply to the compressors
and control circuit power.
3. Remove the shell retaining bolts on the bottom of the econo-
mizer and the bolts that secure the shell to the unit frame or
mounting bracket. Cut the motor cooling line leaving the top
of the economizer. Carefully remove the shell from the
economizer. Make sure EXV plug is still connected. The
economizer shell is heavy. Use caution when removing
shell.
4. Enter the appropriate EXV test step for EXV-A or EXV-B
by pressing
on the HSIO. Scroll down to display
the desired EXV. Press
and
to initiate the test.
Observe the operation of the valve motor and lead screw.
The motor should turn counterclockwise, and the lead screw
should move up out of the motor hub until the valve is fully
open. Lead screw movement should be smooth and uniform
from fully closed to fully open position. Press
as
needed to reach 100% open. Wait 30 seconds in between
each step for motor to stop moving. Press
to check
open to closed operation. If the valve is properly connected
to the processor and receiving correct signals, yet does not
operate as described above, the economizer should be
replaced.
5. Additional items to check for:
a. Verify that float assembly (see cross section view in
Fig. 13) moves up and down freely. It should take only a
minimal force (less than one pound) to move the float and
there should be no binding.
b. Check the bubbler tube (found by carefully lifting the
float) for crimps, etc. and verify that the end of the tube is
open.
6. Reassemble economizer; retorque shell retaining bolts to
35 ft-lb (48 N-m).
If operating problems persist after reassembly, they may be
due to a bad liquid level sensor, suction pressure transducer or
intermittent connections between the processor board terminals
and EXV plug. Recheck all wiring connections and voltage
signals.
Other possible causes of improper refrigerant flow control
could be restrictions in the liquid line. Check for plugged
strainer(s) or restricted metering slots in the EXV or economiz-
er. Formation of ice or frost on lower body of electronic expan-
sion valve is one symptom of restricted metering slots. Howev-
er, frost or ice formation is normally expected when leaving
fluid temperature from the cooler is below 40 F (4.4 C). Clean
or replace valve if necessary.
NOTE (non-economizer units only): Frosting of valve is nor-
mal during compressor test steps and at initial start-up. Frost
should dissipate after 5 to 10 minutes operation in a system
that is operating properly. If valve is to be replaced, wrap valve
with a wet cloth to prevent excessive heat from damaging
internal components.
IMPORTANT: Obtain replacement O-ring before open-
ing EXV. Do not reuse O-rings.
IMPORTANT: When removing top cover from EXVs, be
careful to avoid damage to motor leads.
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IMPORTANT: When removing shell from economizer, it
must be lifted off as close to vertical as possible to prevent
damage to any of the internal parts. Use a catch pan
beneath the economizer as oil will come out when the
shell is removed. Be careful to avoid damage to motor
leads.
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