FOR HVAC INSTALLER ONLY
7.4 Refrigerant Charging
If the refrigerant charge is lost due to service or a leak, a new charge must be accurately weighed in. If any of the old charge is left in the system, it must be recovered before weighing in the new charge. Refer to the unit nameplate for the correct charge weight and refrigerant type.
7.5 Impeller Fan Replacement
The motorized impeller fan is a unitary assembly consisting of the motor and impeller fan. If defective, the complete assembly must be replaced.
1.Unplug the power cord.
2.Remove the cabinet access panel.
3.Remove the screw attaching the impeller fan support bracket to the base.
4.Disconnect the impeller fan leads inside the electric box.
5.Push up on the inlet ring and pull the impeller fan and impeller fan support bracket to the right.
6.Align the bracket with the two notches in the front flange of the base (behind the foam).
7.Slide the impeller fan assembly from the unit.
8.Remove the defective impeller fan from the bracket and replace with it with the new impeller fan.
9.Reassemble the new impeller fan by reversing the above procedure. Note: There are two pins on the backside of the cabinet that must align with the two holes in the impeller fan support bracket.
7.6Compressor/Capacitor Replacement
This compressor is equipped with a two terminal external overload and a run capacitor, but no start capacitor or relay (See Figure 4).
7.6A Checking Compressor Motor Circuits
Perform the following tests if the impeller fan runs but the compressor does not with the fan switch and ventilation timer OFF and the humidity control ON.
1.Unplug the unit; remove the cabinet side and the electrical connection cover on the compressor top.
2.Plug in the unit and turn the humidity control to ON. Check for 110 volts from compressor terminal R to overload terminal 3 using an AC voltmeter. If voltage is present, go to step 3. If no voltage, there may be a loose connection in the compressor circuit. Test each component for continuity. See the appropriate section if a defect is suspected.
3.Unplug the unit, and then disconnect the red and yellow wires from compressor terminals R & S. Using an ohmmeter check continuity between the points listed below.
4.Compressor terminals C and S: No continuity indicates an open start winding. The compressor must be replaced. Normal start winding resistance is 3 to 7 ohms.
5.Compressor terminals C and R: No continuity indicates an open run winding. The compressor must be replaced. Normal run winding resistance is .5 to 2 ohms.
6.Compressor terminal C and overload terminal 1: No continuity indicates a defective overload lead.
7.Overload terminals 1 and 3: If there is no continuity, the overload may be tripped. Wait 10 minutes and try again. If there is still no continuity, it is defective and must be replaced.
8.Compressor terminal C and compressor case: Continuity indicates a grounded motor. The compressor must be replaced.
9.Disconnect the wires from the run capacitor. Set the ohmmeter to the Rx1 scale. The capacitor is shorted and must be replaced if continuity exists across its terminals. If there is no needle movement with the meter set on the Rx100000 scale, the capacitor is open and must be replaced.
10.Reconnect the wires to the compressor and capacitor. Plug in and turn on the unit. If the compressor fails to start, replace the run capacitor.
11.If the unit still does not start, adding a
7.6B Replacing a Burned Out Compressor
The refrigerant and oil mixture in a compressor is chemically very stable under normal operating conditions. However, when an electrical short occurs in the compressor motor, the resulting high temperature arc causes a portion of the refrigerant oil mixture to break down into carbonaceous sludge, a very corrosive acid, and water. These contaminants must be carefully removed otherwise even small residues will attack replacement compressor motors and cause failures.
The following procedure is effective only if the system is monitored after replacing the compressor to insure that the clean up was complete.
1.This procedure assumes that the previously listed compressor motor circuit tests revealed a shorted or open winding.
2.Remove and properly dispose of the system charge. DO NOT vent the refrigerant or allow it to contact your eyes or skin.
3.Remove the burned out compressor. Use rubber gloves if there is any possibility of contacting the oil or sludge.
4.To facilitate subsequent steps, determine the type of burn out that occurred. If the discharge line shows no evidence of sludge and the suction line is also clean or perhaps has some light carbon deposits, the burn out occurred while the compressor was not rotating. Contaminants are therefore largely confined to the compressor housing. A single installation of liquid and suction line filter/driers will probably clean up the system.
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