Cooling Sequence of Operation

364985-XIM-B-0508

under field conditions would be inaccurate. To assure a dry coil, the compressors should be deac- tivated while the test is being run.

4.Knowing the pressure drop across a dry coil, the actual CFM through the unit can be determined from the curve in Pressure Drop vs. Supply Air CFM (Figure 13).

Failure to properly adjust the total system air quantity and static pressure can result in extensive system damage.

After readings have been obtained, remove the tubes and reinstall the two 5/16” dot plugs that were removed in Step 1.

NOTE: De-energize the compressors before taking any test measurements to assure a dry indoor coil.

	0.5
(IWG)	0.4		036	048	060
	0.4

DROP	0.3
DROP
PRESSURE	0.2
PRESSURE
	0.1
	0
	1000	1500	2000	2500	3000

FIGURE 13 - PRESSURE DROP ACROSS COIL

OPERATION

SEQUENCE OF OPERATIONS OVERVIEW

For these units, the thermostat makes a circuit between “R” and “Y1” for the cooling cycle.

The call is passed to the unit control board (UCB), which then determines whether the requested opera- tion is available and, if so, which components to ener- gize.

For heating, the thermostat makes a circuit between “R” and “W1”. The UCB energizes the compressor and condenser fan allowing the unit to run in heating mode. A time / temperature control operates the defrost cycle.

If at any time a call for both heating and cooling are present, the heating operation will be performed. If operating, the cooling system is halted as with a com- pletion of a call for cooling. Heating always takes prior- ity.

CONTINUOUS BLOWER

By setting the room thermostat fan switch to “ON,” the supply air blower will operate continuously.

INTERMITTENT BLOWER

With the room thermostat fan switch set to “AUTO” and the system switch set to either the “AUTO” or “HEAT” settings, the blower is energized whenever a cooling or heating operation is requested. The blower is ener- gized after any specified delay associated with the operation.

When energized, the indoor blower has a minimum run time of 30 seconds. Additionally, the indoor blower has a delay of 10 seconds between operations.

NO OUTDOOR AIR OPTIONS

When the thermostat calls for cooling, the low-voltage control circuit from “R” to “Y1” and “G” is completed. The compressor and condenser fan motor are ener- gized. After completing the specified fan on delay for cooling, the UCB will energize the blower motor.

Once the thermostat has been satisfied, it will de-ener- gize Y1. If the compressor has satisfied its minimum run time, the compressor and condenser fan de-ener- gize. Otherwise, the unit operates the cooling system until the minimum run time for the compressor has been completed. After the compressor de-energizes, the blower is stopped following the elapse of the fan off delay for cooling.

To be available, a compressor must not be locked-out due to a high or low-pressure switch or freezestat trip and the anti-short cycle delay (ASCD) must have elapsed.

Johnson Controls Unitary Products

BQ 048, BQ 036, BQ 060 specifications

Johnson Controls has established itself as a leading player in the HVAC and building management industries, and its BQ series of chillers - including the BQ 060, BQ 036, and BQ 048 - reflects this commitment to innovation and efficiency. These models are designed to provide advanced cooling solutions suitable for a variety of commercial applications.

The BQ 060 is particularly notable for its high-performance capabilities. With a cooling capacity of 60 tons, it utilizes variable-speed compressors, allowing it to adjust its performance based on the cooling demand. This flexibility not only enhances energy efficiency but also reduces operational costs. The unit incorporates advanced microprocessor controls that facilitate seamless integration with building management systems, enabling real-time monitoring and adjustments.

Moving on to the BQ 036, this model is engineered for facilities that require a smaller footprint but still demand reliability and efficiency. With a cooling capacity of 36 tons, it features a compact design without compromising on performance. The BQ 036 also employs environmentally friendly refrigerants, aligning with Johnson Controls' commitment to sustainability. Enhanced insulation and sound-dampening technologies make it an ideal choice for noise-sensitive environments, ensuring comfort without sacrificing efficiency.

The BQ 048 lies in between the two, with a capacity of 48 tons, making it versatile for medium-sized commercial buildings. Its design incorporates a modular approach, allowing for easy scalability in future expansions. This model also features energy recovery options that can utilize excess heat to improve overall efficiency, further solidifying its role in sustainable building practices. Its user-friendly interface enhances operability, simplifying management for building operators.

All three models of the BQ series share key characteristics, such as robust construction to withstand diverse environmental conditions, and low maintenance requirements thanks to their durable components. They utilize advanced technologies for temperature control and energy efficiency, including an intelligent controller that automates more routine tasks. Together, the BQ 060, BQ 036, and BQ 048 offer comprehensive solutions that cater to the growing demands of energy efficiency, sustainability, and reliability in modern building operations. With these chillers, Johnson Controls continues to lead the way in shaping the future of HVAC solutions.