c. Determine which heater(s) need replacing by check- ing resistance on each heater. Refer to paragraph 2.3 for heater resistance values

d. Remove hold-down clamp securing heaters to coil.

e.Lift the bent end of the heater (with the opposite end down and away from coil). Move heater to the side enough to clear the heater end support and remove.

6.16ECONOMIZER, UNLOADER, LIQUID INJEC- TION AND OIL RETURN SOLENOID VALVE

a. Replacing the Coil

NOTE

The coil may be replaced without removing the refrigerant.

1Be sure electrical power is removed from the unit. Disconnect leads. Remove top screw and washer. Lift off coil. (See Figure 6-14 or Figure 6-15)

2Verify coil type, voltage and frequency of old and new coil. This information appears on the coil hous- ing.

b.Replacing Valve Internal Parts (Unloader Solenoid Only)

1Pump down the unit. Refer to paragraph 6.4.

2Be sure electrical power is removed from the unit. Disconnect leads. Remove top screw and washer. Lift off coil. (See Figure 6-14)

3Remove the top screw (see Figure 6-14), washer , and coil assembly.

4Loosen the enclosing tube locknut.

5Remove enclosing tube and locknut assembly. The gasket is inside the enclosing tube.

6Remove seat disc from inside of body and check for obstructions and foreign material.

7Place the seat disc into the valve body with the small- er diameter end facing up.

8Install stem and plunger.

9Place the enclosing tube locknut over the enclosing tube. Install spacer over enclosing tube making sure it is seated properly in the enclosing tube locknut. Tighten enclosing tube locknut to a torque value of 2.78 mkg (20 ft-lb). Do not overtighten.

10Install coil assembly, washer and top screw.

11Evacuate and dehydrate the system. (Refer to section 6.6.) Charge unit with refrigerant per section 6.7.

12Start unit and check operation.

c.Replacing Valve

1 To replace the unloader, liquid injection or econo- mizer valve, pump down the unit. Refer to paragraph

6.4.To replace the oil return valve, remove the re- frigerant charge.

2Be sure electrical power is removed from the unit. Disconnect leads. Remove top screw and washer. Lift off coil. (See Figure 6-14 or Figure 6-15)

3Unbraze valve from unit and braze new valve in place

4Install coil. Evacuate low side and place unit back in operation. Check charge.

1

2

3

4

5

6

7

8

9

1.

Top Screw

6.

Gasket

2.

Washer

7.

Stem and Plunger

3.

Coil

8.

Seat Disc

4.

Locknut

9.

Body

5.

Enclosing Tube

 

 

Figure 6-14. Unloader Solenoid Valve

1

2

3

4

1.

Slotted Screw

4. Enclosing Tube and

2.

Washer

Body

3.

Coil

 

Figure 6-15. Oil Return Solenoid Valve (ORV), Economizer Solenoid Valve (ESV), Liquid Injection Solenoid Valve (LIV)

6.17 EVAPORATOR FAN AND MOTOR ASSEMBLY

The evaporator fans circulate air throughout the container by pulling air in the top of the unit. The air is forced through the evaporator coil where it is either heated or cooled and then discharged out the bottom of

6-11

T-309

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Carrier 69NT20-531-300 manual Start unit and check operation, Unloader Solenoid Valve
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69NT20-531-300 specifications

The Carrier 69NT20-531-300 is a cutting-edge rooftop unit designed to meet the demanding requirements of commercial heating and cooling applications. This model embodies Carrier’s commitment to energy efficiency, reliability, and advanced technological features that enhance indoor comfort while minimizing operational costs.

One of the standout features of the Carrier 69NT20-531-300 is its high energy efficiency. It is equipped with advanced compressor technology that optimizes performance while reducing energy consumption. This ensures that businesses can maintain a comfortable indoor climate without incurring exorbitant utility bills. With a high Seasonal Energy Efficiency Ratio (SEER) and Energy Efficiency Ratio (EER), users can expect not only enhanced comfort but also significant cost savings over time.

The cooling capabilities of the 69NT20-531-300 are complemented by its robust heating options. This unit utilizes a gas heat exchanger, ensuring quick and even heating throughout the space. The combination of cooling and heating capabilities in one compact unit makes it a versatile choice for various applications, including retail spaces, offices, and warehouses.

In addition to its impressive performance specifications, the Carrier 69NT20-531-300 incorporates innovative technologies that further enhance its functionality. The unit comes with advanced controls, allowing for precise temperature regulation and zoning capabilities. This ensures that different areas of a building can maintain their desired temperatures based on usage, improving overall energy efficiency.

Durability is another hallmark of the Carrier 69NT20-531-300. The unit is constructed with high-quality materials and features a weather-proof cabinet that protects it from the elements, ensuring long-term reliability even in harsh conditions. Furthermore, its modular design simplifies maintenance, making it easy for technicians to access critical components.

The 69NT20-531-300 is also designed with low noise operation in mind. It employs sound-dampening technology to ensure that operations are quiet, making it an ideal choice for locations where noise reduction is a priority, such as schools or healthcare facilities.

Overall, the Carrier 69NT20-531-300 stands out as a premier choice for businesses looking for an efficient, reliable, and feature-rich rooftop HVAC unit. Its blend of energy efficiency, advanced technology, and durability positions it as a leader in commercial heating and cooling solutions, making it a valuable investment for any commercial property.
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