Check-out Procedures

NOTE - Refer to outdoor unit installation instructions for system start-up instructions and refrigerant charging instructions.

PRE‐START‐UP CHECKS

SIs the air handler properly and securely installed?

SIf horizontally configured, is the unit sloped up to 5/8 inch toward drain lines?

SWill the unit be accessible for servicing?

SHas an auxiliary pan been provided under the unit with separate drain for units installed above a finished ceiling or in any installation where condensate overflow could cause damage?

SHave ALL unused drain pan ports been properly plugged?

SHas the condensate line been properly sized, run, trapped, pitched, and tested?

SIs the duct system correctly sized, run, sealed, and insulated?

SHave all cabinet openings and wiring been sealed?

SIs the indoor coil factory‐installed TXV properly sized for the outdoor unit being used?

SHave all unused parts and packaging been disposed of?

SIs the filter clean, in place, and of adequate size?

SIs the wiring neat, correct, and in accordance with the wiring diagram?

SIs the unit properly grounded and protected (fused)?

SIs the thermostat correctly wired and in a good location?

SAre all access panels in place and secure?

CHECK BLOWER OPERATION

SSet thermostat to FAN ON.

SThe indoor blower should come on.

CHECK COOLING OPERATION

S Set thermostat to force a call for cooling (approximately 5ºF lower than the indoor ambient temperature).

SThe outdoor and indoor units should come on immediately.

SCheck the airflow from a register to confirm that the system is moving cooled air.

SSet the thermostat 5ºF higher than the indoor temperature. The indoor blower and outdoor unit should cycle off. Air handler should cycle off 45 seconds after the outdoor unit shuts off.

CHECK ELECTRIC HEATER (IF USED)

SSet thermostat to call for auxiliary heat (approximately 5°F above ambient temperature). The indoor blower and auxiliary heat should come on together. Allow a minimum of 3 minutes for all sequencers to cycle on.

SSet the thermostat so that it does not call for heat. Allow up to 5 minutes for all sequencers to cycle off.

Operation

TIME DELAY RELAY

Blower time delay operation:

1.When cooling demand is initiated, there is a 1 second motor-on delay.

2.After the motor-on delay expires, motor ramps up to 100% and runs at 100% until cooling demand is satisfied.

3.Once demand is met, motor runs at 100% for 45 seconds.

4.Motor ramps down to stop.

		3	4
1	2	100%	100%
1	2	CFM	CFM
	1		OFF
	1
SECOND		COOLING	45
DELAY		COOLING	45
DELAY		DEMAND	SECS
		DEMAND	SECS

Figure 14. Blower Time Delay

COOLING (COOLING ONLY OR HEAT PUMP)

When the thermostat calls for cooling, 24 volts is put on the blower time-delay relay coil and then the indoor blower relay energizes. The normally open contacts close, causing the indoor blower motor to operate. The circuit between R and Y is completed, closing the circuit to the contactor in the outdoor unit, starting the compressor and outdoor fan motor.

On heat pumps, circuit R and O energizes the reversing valve, switching the valve to the cooling position. (The reversing valve remains energized as long as the thermostat selector switch is in the COOL position.)

At the completion of the cooling demand the indoor blower and outdoor unit should cycle off. Air handler should cycle off 45 seconds after the outdoor unit shuts off.

HEATING (ELECTRIC HEAT ONLY)

When the thermostat calls for heat, the circuit between R and W is completed, and the heat sequencer is energized. A time delay follows before the heating elements and the indoor blower motor come on. Units with a second heat sequencer can be connected with the first sequencer to W on the thermostat subbase, or they may also be connected to a second stage on the subbase.

HEATING (HEAT PUMP)

When the thermostat calls for heating, 24 volts is put on the blower time-delay relay coil. Then normally open contacts close, causing the indoor blower motor to operate. The circuit between R and Y is completed, closing the circuit to the contactor in the outdoor unit, starting the compressor and outdoor fan motor.

If the room temperature should continue to fall, the circuit between R and W1 is completed by the second‐stage heat room thermostat. Circuit R-W1energizes a heat sequencer. The completed circuit will energize supplemental electric heat (if applicable). Units with a

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Merit CBX25UH Series, Lennox Air Handler specifications

Lennox International Inc is a leading provider of innovative HVAC systems, and among its standout products is the Merit CBX25UH Series, an advanced air handler designed to enhance indoor comfort while ensuring energy efficiency. This series is specifically designed for use with the Lennox cooling and heating systems, making it an ideal choice for homeowners seeking versatile climate control solutions.

One of the primary features of the Merit CBX25UH Series is its multi-position installation capability, allowing it to be configured for upflow, downflow, or horizontal airflow. This flexibility makes it suitable for a wide range of home layouts and needs. The series is designed for use with a variety of Lennox outdoor units, ensuring seamless integration into existing HVAC systems.

The air handler is equipped with a high-efficiency blower motor that optimizes airflow, enhancing indoor comfort while minimizing energy consumption. This variable-speed blower motor not only operates quietly but also adjusts airflow based on the specific heating or cooling demands of the home. This feature significantly improves energy efficiency, helping homeowners save on utility bills while reducing their environmental impact.

Another key technology in the Merit CBX25UH Series is its SmartLynx™ communicating technology, which allows for efficient communication between the air handler and other HVAC components. This advanced communication ensures that the system operates at peak performance, providing consistent and reliable heating and cooling throughout the space.

The CBX25UH also boasts a durable cabinet that offers excellent insulation, minimizing energy loss and enhancing overall system efficiency. The cabinet's design reduces noise levels, contributing to a more peaceful indoor environment. Additionally, the air handler features a robust filtration system that helps maintain indoor air quality by capturing dust and allergens, ensuring a healthier living space.

Lastly, the Merit CBX25UH Series is backed by Lennox’s renowned reliability and quality. Homeowners can have peace of mind knowing they are investing in a product designed to deliver dependable performance for years to come. Overall, the Merit CBX25UH Series is a top choice for those seeking a powerful, efficient, and flexible air handling solution within their HVAC system.