Daikin WMC Specifications download pdf (Page 13)

Catalog 602-2 13

Electronic Expansion Valve

Controlled refrigerant flow over the entire capacity

range saves energy and dollars. Cooling loads and

condenser water temperatures can change

constantly. On Magnitude chillers, a modern

electronic expansion valve meters refrigerant flow

in direct response to the unit controller input,

which looks at unit kW and lift (discharge minus

suction pressure) to set the valve position. The

controller then balances suction superheat and

liquid subcooling to reach the optimum efficiency,

regardless of changing load or condensing

temperatures. In doing so, full utilization of

compressor, evaporator, and condenser efficiency

over the entire operating range is achieved.

Flow Switch

All chiller units must be provided with flow

switches for the evaporator and condenser. Daikin

McQuay furnishes factory-installed and wired,

thermal dispersion-type flow switches as standard

equipment on Magnitude chillers. This eliminates

the expense of field mounting and wiring

conventional paddle or differential pressure

switches.

The flow switches

prevent the unit

from starting

without sufficient

water flow through

the vessels. They

also serve to shut

down the unit in

the event that

water flow is

interrupted to

guard against evaporator freeze-up or excessive

discharge pressure.

Additionally, for a higher margin of protection,

normally open auxiliary contacts in the pump

starters can be wired in series with the flow switches

as shown in the Field Wiring Diagram.

Factory Performance Test

Fast and trouble free startup and operation

All Daikin McQuay centrifugal chillers are factory-

tested on AHRI qualified microprocessor-controlled

test stands. The test stand microprocessors interface

with the chiller MicroTech controls, allowing

monitoring of all aspects of the test stand and chiller

operation.

The test procedure starts with dehydration and

evacuation of the refrigerant circuit and charging

with refrigerant. This is followed by a run test at job

conditions of flow and temperature. Compressors

must meet a stringent vibration limit and the entire

unit must pass a moisture limit of 30 ppm.

The testing helps ensure correct operation prior to

shipment and allows factory calibration of chiller

operating controls.

Optional Certified Test

A factory engineer oversees the testing, certifies the

accuracy of the computerized results, and translates

the test data onto an easy-to-read spreadsheet. The

tests are run to AHRI tolerance of capacity and

power. 50 Hertz units are tested using an on-site 50

Hertz generator.

Optional Witness Test

A factory engineer oversees the testing in the

presence of the customer or their designate and

translates the test data onto an easy-to-read

spreadsheet. Tests are run to AHRI tolerances of

capacity and power. 50 Hertz units are tested using

an on-site 50 Hertz generator.

McQuay Factory Service Startup

All Daikin McQuay centrifugal chillers are

commissioned by local McQuay Factory Service

personnel or by authorized McQuay startup

technicians. This procedure helps assure that proper

starting and checkout procedures are employed and

helps speed up the commissioning process.

Part Load Efficiency

According to ASHRAE, chillers usually spend

99% of their operating hours under part load

conditions and most of this time at less than 60%

of design capacity. One compressor of a dual

chiller operates with the full heat transfer surface

of the entire unit. For example, one 75-ton

compressor on a 150-ton dual chiller utilizes 150

tons of evaporator and condenser surface. This

results in very high unit efficiency and also

increases the compressor’s capacity.

The inclusion of VFDs, as standard, to the dual

compressor chiller can produce astonishing AHRI

Certified IPLVs,

as low as 0.328 kW/ton. Specific

selections can vary from this example.

Compliance with ASHRAE Std. 90.1

With the Magnitude chiller capacity range of 145

to 400 tons, they fall into three ASHRAE Std. 90.1

efficiency groups and revisions.

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Daikin WMC Specifications Page 13

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