Therma-Stor Products Group UA-150H - Manual (Page 17)

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.
7.6 Compressor/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 hard-start kit (relay &
capacitor) will provide greater starting torque. If this doesn't
work, the compressor has an internal mechanical defect and
must be replaced.
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.
FOR HVAC INSTALLER ONLY
17 Ultra-Aire 150H Installer’s & Owner’s Manual