O

T2 C C O

DFT

 

 

 

 

 

OF2

OF1

R

T1

 

 

 

 

 

 

 

 

W

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

Y

 

 

 

 

 

 

 

 

 

C

Y

 

 

 

 

 

 

 

 

SPEEDUP

P1

 

 

 

 

 

 

 

 

J1

P3

INTERVALTIMER

90

60 30

30 60

120

 

 

 

DFT

 

OFF

 

QUIET SHIFT

ON

 

 

 

Speedup

 

 

 

 

Quiet

Defrost interval

 

 

Pins

 

 

 

 

Shift

DIP switches

 

 

 

 

 

 

 

 

 

 

A08020

Fig. 24 - Defrost Control

48EZ -- A

!WARNING

EXPLOSION, PERSONAL INJURY AND ENVIRONMENTAL HAZARD

Failure to follow this warning could result in personal injury, death or property damage.

System under pressure. Relieve pressure and recover all refrigerant before system repair or final unit disposal. Use all service ports and open all flow-control devices, including solenoid valves.

If oil is detected or if low cooling performance is suspected, leak-test all refrigerant tubing using an electronic leak-detector, halide torch, or liquid-soap solution. If a refrigerant leak is detected, refer to the Check for Refrigerant Leaks section.

If no refrigerant leaks are found and low cooling performance is suspected, refer to the Checking and Adjusting Refrigerant Charge section.

Gas Input

The gas input does not require checking unless improper heating performance is suspected. If a problem exists, refer to the Start-Up section.

Indoor Airflow

The heating and/or cooling airflow does not require checking unless improper performance is suspected. If a problem exists, be sure that all supply- and return-air grilles are open and free from obstructions, and that the air filter is clean. When necessary, refer to

the Indoor Airflow and Airflow Adjustments section to check the system airflow.

Check Defrost Thermostat

The defrost thermostat is usually located on the lowest liquid leaving circuit of the left condenser coil (see Fig. 22). The thermostat closes at 32_F (0_C) and opens at 65_F (18_C).

Puron Items

Metering Device (Thermostatic Expansion Valve & Piston)

This unit uses both a hard shutoff, balance port TXV in the indoor coil and a piston in each side of the outdoor coil. The TXV maintains a constant superheat at the evaporator coil exit (cooling mode) resulting in higher overall system efficiency.

Pressure Switches

Pressure switches are protective devices wired into control circuit (low voltage). They shut off compressor if abnormally high or low pressures are present in the refrigeration circuit. These pressure switches are specifically designed to operate with Puron (R-410A) systems. R-22 pressure switches must not be used as replacements for the Puron (R-410A) system.

Loss of Charge Switch

This switch is located on the liquid line and protects against low suction pressures caused by such events as loss of charge, low airflow across indoor coil, dirty filters, etc. It opens on a pressure drop at about 20 psig. If system pressure is above this, switch should be closed. To check switch:

1. Turn off all power to unit.

31

Page 30 Page 32
Page 31
Image 31
Carrier 48EZ-A Gas Input, Indoor Airflow, Check Defrost Thermostat, Puron Items, Pressure Switches, Loss of Charge Switch
Page 30 Page 32

48EZ-A specifications

The Carrier 48EZ-A and 48VT-A are two advanced rooftop unit air conditioners that exemplify innovation and efficiency in HVAC technology. Designed for commercial applications, these units provide optimal comfort while ensuring energy conservation and reliability.

One of the standout features of the Carrier 48EZ-A is its high-efficiency cooling system. With SEER ratings reaching up to 16, this model uses advanced compressor technology to ensure that energy consumption stays low while maximizing cooling output. The 48EZ-A incorporates a two-stage scroll compressor that enhances performance during partial load conditions, making it ideal for varying temperature demands throughout the day.

Meanwhile, the Carrier 48VT-A is designed with variable speed technology that allows for precise modulation of airflow and cooling capacity, adapting seamlessly to real-time building conditions. This technology not only improves comfort but also significantly reduces energy usage by optimizing operational efficiency.

Both units are equipped with advanced microprocessor controls that facilitate superior management of the HVAC system. The controls offer programmable options allowing for enhanced control over system operation, scheduling, and diagnostics. This promotes easy maintenance and ensures long-term reliability.

In terms of construction, the Carrier 48EZ-A and 48VT-A units are built with corrosion-resistant materials, ensuring durability and longevity even in challenging environments. The cabinet is designed with insulated panels to minimize sound levels, making them suitable for installation in noise-sensitive locations.

Moreover, both models are equipped for easy installation and serviceability. The logical wiring design and access ports streamline maintenance, reducing downtime and optimizing overall performance. Additionally, they feature an energy-efficient fan design that maximizes airflow while minimizing energy use.

In summary, the Carrier 48EZ-A and 48VT-A rooftop units stand out in the HVAC market for their energy efficiency, advanced technology, and durable construction. These features make them ideal choices for various commercial applications where comfort, efficiency, and reliability are paramount. The combination of high-performance components and user-friendly features positions these models as leaders in modern HVAC solutions.
Top Page Image Contents