20
MOLECULAR SIEVE BEDS
The two molecular sieve beds alternately remove the nitrogen
from the air passing through them and provide the patient
with a constant supply of oxygen.
The efficiency of the molecular sieve material will be impaired
if it becomes contaminated by moisture. Contamination causes
the molecular sieve material to lose its nitrogen adsorbing
properties resulting in a decrease in oxygen concentration.
The unit should run for a minimum of 20 minutes before turn-
ing "Off" to prevent problems associated with moisture conta-
mination in the system.
To test the sieve beds:
1. Remove the 1/16" plugged piece of tubing from the top of
each sieve bed.
2. Connect the pressure-vacuum gauges to the sieve bed test
points (Figure 9) in order to observe unit cycling and bed
pressures. Refer to the section on “Normal Operating
Sequence.”
3. If it is determined that the four-way did not shift, refer to the
section on four-way testing. However, if the unit is cycling prop-
erly allow unit to run while observing the sieve bed pressures.
4. After 20 minutes of operation, check the oxygen concentra-
tion levels. Low oxygen concentration and high pressures indi-
cate contaminated sieve beds.
NOTE: If the molecular sieve material is found to be no longer
effective, first locate the source of the malfunction or cause
(such as leaks) for contamination and take corrective action.
To replace the molecular sieve beds (Figure 7):
1. Make sure any contamination problem has been corrected
before replacing.
2. Make sure the unit is unplugged from the wall outlet.
3. Cut the plastic cable ties that secure the sieve beds to the
internal structure of the unit.
4. Remove the tubing from the fittings at the top of each sieve bed.
5. Remove the hose clamps and black hose from the bottom of
the sieve beds.
6. Install new sieve beds in reverse order using new plastic cable
ties. Position the new beds so that the bed serial number label
is at the top of the unit.
NOTE: Make sure that the sealing caps remain on the new
sieve beds until just prior to connecting hoses and tubing.
7. Leak test all connections with a certified leak detection solution.
OSD
®
(early OSD models)
The OSD is located beside the PC board.
To replace the OSD:
1. Ensure the unit is unplugged from the wall outlet.
2. Remove the front and back cabinets and loosen the bib.
3. Disconnect the two terminal connectors for the OSD at the
end of the wire harness by depressing the latches and pulling
them straight out.
NOTE: To facilitate easier access to the OSD tubing, remove
the 2 screws that hold the main PC board in place.
4. Remove the two screws from the bracket located on the side
facing the inner structure.
5. Remove the two hose clamps and two hoses attached to the
OSD.
6. Replace the two hoses and tighten the hose clamps to the
new OSD.
7. Mount the OSD to the bracket using the two screws.
8. Reconnect the two terminal connectors.
9. Reinstall main PC board screws if they were removed.
NOTE:The OSD on later models is integrated into
the printed circuit board. See “Printed Circuit Board”
section for removal and replacement.
POWER CORD
To replace the power cord - 115 volt units only
(Figure 10):
1. Make sure the unit is unplugged from the wall outlet.
2. Remove the back cabinet.
3. Disconnect the power cord connector.
NOTE: Loosening or removing the compressor mounting
plate may make it easier to service the power cord.
4. Note wire colors and socket locations before removing wires.
5. Using a pair of duckbill pliers, squeeze the power cord strain
relief and pull it out of the base of the unit.
6. Insert a new power cord through the hole in the base of the
unit and secure with strain relief.
7. Insert sockets into connector housing and then reconnect the
power cord connector.
8. Replace back cabinet and secure with the six screws.
POWER SWITCH
To replace the power switch (Figure 8):
1. Make sure the unit is unplugged from the wall outlet.
2. Remove the front and back cabinets and loosen the bib.
3. Note the position of the wires and switch before removing
the wires from the switch terminals.
4. While squeezing the locking tabs on the sides of the switch,
push the switch out of the front of the bib.
5. Install the new switch in the correct orientation making sure
that it locks into position.
6. Reconnect the wires to the switch terminals.
COMPONENT TESTING, REPAIR, AND REPLACEMENT
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