TK 61753-2-MM-EN
95
Testing for an Overcharge
Use the following procedure to identify a Thermo King unit with an excessive refrigerant charge:
1. Install a calibrated gauge manifold on the compressor.
2. Operate the host unit in high speed with all zones in cool long enough to stabilize system pressures and reduce the
compartment temperatures to approximately 16 C (60 F)or colder.
3. Observe discharge pressure and cover the condenser to increase the discharge pressure approximately 75 to 100
psig (5.0 to 6.9 bar) above observed pressure. It is located on the side of the unit, above the control panel.
NNoottee:: If the liquid level in the receiver sight glass drops during step 3, the unit is not overcharged and it is not
necessary to complete the rest of the procedure.
4. Remove the condenser cover to rapidly reduce discharge pressure.
5. Observe the receiver tank sight glass and the unit discharge pressure.
6. By the time the discharge pressure drops approximately 50 psig (3.45 bar), the liquid level in the receiver tank
should drop.
a. When the discharge pressure stabilizes, the ball and liquid level will rise to the previous level.
b. If the liquid level will not drop, the unit most likely has an overcharge of refrigerant. The refrigerant level should
be adjusted.
To remove refrigerant:
1. Connect and purge/evacuate a gauge manifold set to the receiver tank outlet valve and an approved sealed
container.
2. Operate the unit in high speed COOL .
3. Use a gauge manifold set from step 1 to pump refrigerant from the receiver tank into the approved sealed container.
4. When the liquid level begins to decline in the receiver tank sight glass (bottom sight glass on two sight glass
receiver tank), close the hand valve on the gauge manifold immediately. Allow the new liquid level in the sight glass
to stabilise (1 to 2 minutes).
• If the refrigerant level is still too high, repeat steps 2 through 4.
• Once the refrigerant level is ok, perform a complete refrigerant level check and repeat the overcharge test.
5. Always recover remaining refrigerant from the hoses before disconnecting the gauge manifold set from the unit.
6. Repeat the overcharge test.
Filling refrigerant to an empty system:
1. Connect and purge/evacuate a gauge manifold set to a refrigerant bottle and the suction service valve.
2. Set the refrigerant bottle for liquid charging.
3. Operate the unit in high speed COOL .
4. Open the valve on the refrigerant bottle and read the suction pressure on the gauge manifold.
5. Add liquid refrigerant through the suction service valve. Open the gauge manifold low pressure hand valve only
enough to permit suction pressure to increase 1.40 bar, 25 psi. This will meter liquid refrigerant slowly into the low
side.
6. Add refrigerant until the ball 1/4 to 1/3 of the sight glass (bottom sight glass on two sight glass receiver tank). Allow
the level to stabilise (1 to 2 minutes).
• If the refrigerant level is still too low, add more refrigerant and allow to stabilise once more.
• Once the refrigerant level is ok, perform a complete refrigerant level check and repeat the overcharge test.
NNOOTTIICCEE
SSyysstteemm CCoonnttaammiinnaattiioonn!!
TTaakkee nnoottee ooff tthhee rreeffrriiggeerraanntt ttyyppee ((llaabbeell oonn oouuttssiiddee ooff uunniitt)) aanndd ddoo nnoott ccrroossss--ccoonnttaammiinnaattee..
7. Always recover remaining refrigerant from the hoses before disconnecting the gauge manifold set from the unit.
8. Repeat the overcharge test.
RReeffrriiggeerraattiioonn MMaaiinntteennaannccee
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