Carrier 69NT40-541-001, Operation And Service

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7–21 T-316
8. Following the water flush, circulate a 56.7 gram (2 ounce) per 3.785 liter (1 U.S. gallon) solution of
Oakite No. 22 thru the tubes to neutralize. Drain this solution.
9. Flush the tubes thoroughly with fresh water.
NOTE
If the condenser cooling water is not being used as drinking water or is not re-circulated in a closed or
tower system, neutralizing is not necessary.
10. Put the unit back in service and operate under normal load. Check the head pressure. If normal, a thorough
de-scaling has been achieved.
What You Can Do For Further Help:
Contact the Engineering and Service Department of the OAKITE PRODUCTS CO., 19 Rector Street, New York,
NY 10006 U.S.A. for the name and address of the service representative in your area.
7.13 FILTER-DRIER
On units equipped with a water-cooled condenser, if the sight glass appears to be flashing or bubbles are con-
stantly moving through the sight glass when the suction modulation valve is fully open, the unit may have a low
refrigerant charge or the filter-drier could be partially plugged.
a. To Check Filter-Drier
1. Test for a restricted or plugged filter-drier by feeling the liquid line inlet and outlet connections of the drier
cartridge. If the outlet side feels cooler than the inlet side, then the filter-drier should be changed.
2. Check the moisture-liquid indicator if the indicator shows a high level of moisture, the filter-drier should be
replaced.
b. To Replace Filter-Drier
1. Pump down the unit and replace filter-drier.
2. Evacuate the system in accordance with Section 7.6 .
3. After unit is in operation, inspect for moisture in system and check charge.
7.14 THERMOSTATIC EXPANSION VALVE
The thermal expansion valve (see Figure 7.19 ) is an automatic device which maintains constant superheat of the
refrigerant gas leaving the evaporator, regardless of suction pressure.
The valve functions are:
1. Automatic control of the refrigerant flow to match the evaporator load.
2. Prevention of liquid refrigerant entering the compressor.
Unless the valve is defective, it seldom requires maintenance other than periodic inspection to ensure that the ther-
mal bulb is tightly secured to the suction line and wrapped with insulating compound. (See
Figure 7.19 )
Figure 7.19 Thermostatic Expansion Valve Bulb
Suction Line
TXV Bulb Clamp
Nut and Bolt
TXV Bulb