Start-Up, Check for Refrigerant Leaks

4. Verify the following conditions:

a.Make sure gas line is free of air. Before lighting the unit for the first time, perform the following with the gas valve in the “OFF” position:

NOTE: If the gas supply pipe was not purged before connecting the unit, it will be full of air. It is recommended that the ground joint union be loosened, and the supply line be allowed to purge until the odor of gas is detected. Never purge gas lines into a combustion chamber. Immediately upon detection of gas odor, retighten the union. Allow 5 minutes to elapse, then light unit.

b.Make sure that condenser-fan blade is correctly positioned in fan orifice. Leading edge of condenser-fan blade should be 1/2 in. (12 mm) maximum from fan orifice.

c.Make sure that air filter(s) is in place.

d.Make sure that condensate drain trap is filled with water to ensure proper drainage.

e.Make sure that all tools and miscellaneous loose parts have been removed.

START-UP

Step 1 — Check for Refrigerant Leaks

Proceed as follows to locate and repair a refrigerant leak and to charge the unit:

1.Locate leak and make sure that refrigerant system pressure has been relieved and reclaimed from both high- and low-pressure ports.

2.Repair leak following Refrigerant Service procedures. NOTE: Install a bi-flow filter drier whenever the system has been opened for repair.

3.Add a small charge of R-410A refrigerant vapor to system and leak-test unit.

4.Recover refrigerant from refrigerant system and evacuate to 500 microns if no additional leaks are not found.

5.Charge unit with Puron (R-410A) refrigerant, using an electronic scale. Refer to unit rating plate for required charge.

Step 2 — Unit Sequence of Operation

48EZ-A Sequence of Operation

a. CONTINUOUS FAN

(1.) Thermostat closes circuit R to G energizing the blower motor for continuous fan.

b. COOLING MODE

(1.) If indoor temperature is above temperature set point thermostat closes circuits R to G, R to Y and R to O-The unit delivers cooling airflow.

c.HEAT PUMP HEATING MODE

Outdoor temperature above balance point setpoint of thermostat.

(1.) On a call for heating, terminals “Y” and “G“ of the Hybrid thermostat are energized. The “Y“ signal is sent to the Defrost Board (DB) terminal “Y”. The DB has a built in five minute anti-short cycle timer which will not allow the compressor to restart before the time delay has expired.

(2.) “T2” energizes the compressor contactor via the High Pressure Switch (HPS) and Low Pressure Switch (LPS). The compressor and outdoor fan start. Thermostat “G” energizes the Interface Fan Board terminal “G”. The blower motor is energized through contacts of the IFB.

(3.) When the thermostat removes the “Y” and “G” calls, the compressor contactor and outdoor fan are

de-energized. The evaporator motor is de-ener- gized after a 90 sec. delay.

d.GAS HEATING MODE

Outdoor temperature below balance point setpoint of thermostat.

Heating Sequence of Operation

(See Fig. 15 and 16 and unit wiring label.)
On a call for heating, terminal W of the thermostat is energized,
starting the induced-draft motor. When the pressure switch senses
that the induced-draft motor is moving sufficient combustion air,
the burner sequence begins. This function is performed by the
integrated gas unit controller (IGC). The indoor (evaporator)-fan
motor is energized 45 sec after flame is established. When the
thermostat is satisfied and W is de-energized, the burners stop
firing and the indoor (evaporator) fan motor	shuts off after a
45-sec time-off delay. Please note that the IGC	has the capability
to automatically reduce the indoor fan motor on delay and increase
the indoor fan motor off delay in the event of high duct static
and/or partially-clogged filter.
NOTE: An LED (light-emitting diode) indicator is provided on		A
		--
the control board to monitor operation. The control board is		--
		48EZ
located by removing the burner access panel (see Fig. 19). During
normal operation, the LED is continuously on.

Step 3 — Start-up Heating and Make Adjust- ments

!CAUTION

UNIT COMPONENT DAMAGE HAZARD

Failure to follow this caution may result in damage to the unit being installed.

Complete the required procedures given in the Pre-Start-Up section before starting the unit. Do not jumper any safety devices when operating the unit.

Complete the required procedures given in the Pre-Start-Up section before starting the unit. Do not jumper any safety devices when operating the unit. Make sure that burner orifices are properly aligned. Unstable operation my occur when the burner orifices in the manifold are misaligned.

Follow the lighting instructions on the heating section operation label (located on the inside of the control access panel) to start the heating section.

NOTE: Make sure that gas supply has been purged, and that all gas piping has been checked for leaks.

Pipe Plug	Manifold

A07679

Fig. 11 - Burner Assembly

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.

Carrier 48EZ-A Start-Up, Check for Refrigerant Leaks, Unit Sequence of Operation

Models: 48EZ-A