Daikin WMC Specifications download pdf (Page 43)

Catalog 602-2 43

determined from the Daikin McQuay selection

program.

We recommend variable flow only in the

evaporator because there is virtually no change in

chiller efficiency compared to constant flow. In

other words, there is no chiller energy penalty and

considerable pumping energy can be saved.

Although variable speed pumping can be done in

the condenser loop, it is usually unwise. The intent

of variable flow is to reduce pump horsepower.

However, reducing condenser water flow increases

the chiller’s condensing pressure, increasing the

lift that the compressor must overcome which, in

turn, increases the compressor’s energy use.

Consequently, pump energy savings can be lost

because the chiller operating power is significantly

increased.

Low condenser flow and tube velocities can cause

premature tube fouling and subsequent increased

compressor power consumption. Increased

cleaning and/or chemical use can also result.

Vibration Mounting

The Magnitude chillers are almost vibration-free.

Consequently, floor mounted spring isolators are

not usually required. Rubber mounting pads are

shipped with each unit. It is wise to continue to

use piping flexible connectors to reduce sound

transmitted into the pipe and to allow for

expansion and contraction.

System Water Volume

All chilled water systems need adequate time to

recognize a load change, respond to that load

change and stabilize, without undesirable short

cycling of the compressors or loss of control. In

air conditioning systems, the potential for short

cycling usually exists when the building load falls

below the minimum chiller plant capacity or on

close-coupled systems with very small water

volumes.

Some of the things the designer should consider

when looking at water volume are the minimum

cooling load, the minimum chiller plant capacity

during the low load period and the desired cycle

time for the compressors.

Assuming that there are no sudden load changes

and the chiller plant has reasonable turndown, a

rule of thumb of “gallons of water volume equal

to two to three times the chilled water gpm flow

rate” is often used.

A properly designed storage tank should be

added if the system components do not provide

sufficient water volume.

Pump Control

Operation of the chilled water pump can be to:

1) cycle the pump with the unit

2) operate continuously

3) cycle automatically by a remote source

The cooling tower pump must cycle with the

compressor. The holding coil of the cooling

tower pump motor starter must be rated at 115

volts, 60 Hz, with a maximum volt-amperage

rating of 100. A control relay is required if the

voltage-amperage rating is exceeded. See the

Field Wiring Diagram on page 38 or in the

cover of control panel for proper connections.

All interlock contacts m

ust be rated for no less

than 10 inductive amps. The alarm circuit

provided in the control center utilizes 115-volts

AC. The alarm used must not draw more than

10-volt amperes.

System analysis

Although McQuay International is a proponent

of analyzing the entire system, it is generally

effective to place the chiller in the most

efficient mode because it is a large energy

consumer.

The McQuay Energy Analyzer program is an

excellent tool to investigate the entire system

efficiency, quickly and accurately. It is

especially good at comparing different system

types and operating parameters. Contact you

local Daikin McQuay sales office for assistance

on your particular application.

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Daikin WMC Specifications Page 43

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