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 (refer to paragraph 6.4 and replace filter-drier.

2.Evacuate the low side in accordance with paragraph 6.6.

3.After unit is in operation, inspect for moisture in sys- tem and check charge.

6.14 EXPANSION VALVES

Two expansion valves are used, the evaporator

expansion valve (item 9, Figure 2-2), and the economizer expansion valve (item 26, Figure 2-4) .The

expansion valves are automatic devices which maintain constant superheat of the refrigerant gas leaving at the point of bulb attachment regardless of suction pressure.

The valve functions are:

1.Automatic control of the refrigerant flow to match the load.

2.Prevention of liquid refrigerant entering the com- pressor.

Unless the valve is defective, it seldom requires maintenance other than periodic inspection to ensure that the thermal bulb is tightly secured to the suction line

and

wrapped with

insulating compound. (See

Figure 6-10.)

 

 

 

3

 

 

 

2

 

4

 

1

 

 

 

 

1.

Suction Line

3.

Nut and Bolt

2.

TXV Bulb Clamp

4.

TXV Bulb

Figure 6-10 Thermostatic Expansion Valve Bulb 6.14.1 Checking Superheat.

NOTE

Proper superheat measurement for the evapora- tor expansion valve should be completed at -18_C (0_F) container box temperature where possible. If the economizer valve is suspect, it should be replaced.

6-9

a. Open the heater access panel (see Figure 2-1) to ex- pose the evaporator expansion valve.

b.Attach a temperature sensor near the expansion valve bulb and insulate. Make sure the suction line is clean and that firm contact is made with the sensor.

c.Connect an accurate gauge to the service port directly upstream of the suction modulating valve.

d.Set the temperature set point to -18_C (0_F), and run unit until conditions stabilize.

e.The readings may cycle from a high to a low reading. Take readings of temperature and pressure every three to five minutes for a total of 5or 6 readings

f.From the temperature/pressure chart (Table 6-7), de- termine the saturation temperature corresponding to the evaporator outlet test pressures at the suction modulation valve.

g.Subtract the saturation temperatures determined in step f. from the temperatures measured in step e.. The difference is the superheat of the suction gas. Deter- mine the average superheat It should be 4.5 to 6.7 °C (8 to 12 °F)

6.14.2 Valve Replacement

a. Removing the Expansion Valve

NOTES

1.The TXV’s are hermetic valves and do not have adjustable superheat.

2.All connections on the evaporator TXV are bi---metallic, copper on the inside and stainless on the outside. When brazing, bi---metallic connections heat up very quickly.

6

1

2

5

3

4

1.Evaporator Expansion Valve

2.Non-adjustable Superheat Stem

3.Equalizer Connection

4.Inlet Connection

5.Outlet Connection

6.Expansion Valve Bulb

Figure 6-11 Evaporator Expansion Valve

T-309

Page 72 Page 74
Page 73
Image 73
Carrier 69NT20-531-300 manual Two expansion valves are used, the evaporator, Wrapped with Insulating compound. See
Page 72 Page 74

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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