REMEDY/

CONDITION

POSSIBLE CAUSE

REFERENCE

 

 

SECTION

5.3 UNIT RUNS BUT HAS INSUFFICIENT COOLING

 

 

 

 

 

Abnormal pressures

5.7

 

 

 

 

Abnormal temperatures

5.15

 

 

 

 

Abnormal currents

5.16

 

 

 

 

Controller malfunction

5.9

 

 

 

 

Evaporator fan or motor defective

6.17

 

 

 

 

Shortage of refrigerant

6.7.1

Refrigeration System

 

 

Suction modulation valve lost track of step count

Power cycle

 

 

 

 

Suction modulation valve malfunction

6.20

 

 

 

 

Compressor service valves or liquid line shutoff valve par-

Open valves

 

tially closed

completely

 

Economizer solenoid valve or TXV malfunction

6.14, 6.19

 

 

 

 

Unloader valve stuck open

6.19

 

 

 

 

Frost on coil

5.10

 

 

 

5.4 UNIT WILL NOT HEAT OR HAS INSUFFICIENT HEATING

 

 

 

 

 

Start-Stop switch OFF or defective

Check

 

 

 

No operation of any kind

Circuit breaker OFF or defective

Check

 

External power source OFF

Turn ON

 

 

 

 

Circuit breaker or fuse defective

Replace

 

 

 

 

Control Transformer defective

Replace

 

 

 

No control power

Evaporator fan internal motor protector open

6.17

 

Heat relay defective

Check

 

 

 

 

Heater termination thermostat open

6.15

 

 

 

 

Heater(s) defective

6.15

 

 

 

 

Heater contactor or coil defective

Replace

 

 

 

 

Evaporator fan motor(s) defective or rotating backwards

6.15/6.17

 

 

 

Unit will not heat or has insuffi-

Evaporator fan motor contactor defective

Replace

cient heat

Controller malfunction

5.9

 

 

 

 

Defective wiring

Replace

 

 

 

 

Loose terminal connections

Tighten

 

 

 

 

Low line voltage

2.3

 

 

 

5.5 UNIT WILL NOT TERMINATE HEATING

 

 

 

 

 

Controller improperly set

Reset

 

 

 

Unit fails to stop heating

Controller malfunction

5.9

 

 

Heater termination thermostat remains closed along with

6.15

 

 

the heat relay

 

 

 

 

 

5.6 UNIT WILL NOT DEFROST PROPERLY

 

 

 

 

 

Defrost timer malfunction (Cd27)

Table 3-5

 

Loose terminal connections

Tighten/

 

 

 

Will not initiate defrost

Defective wiring

Replace

automatically

 

 

Defrost temperature sensor defective or heat termination

Replace

 

thermostat open

 

 

 

 

 

 

Heater contactor or coil defective

Replace

T-309

5-2

Page 61
Image 61
Carrier 69NT20-531-300 manual Unit will not heat or has insuffi

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.

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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.