Installation manual

50 Magnitude™ Frictionless Centrifugal Chillers – Model WMC IM 1029-2
Since there are many other factors that can influence performance, systems may successfully operate below
these suggestions. However, as the water volume decreases below these suggestions, the possibility of problems
increases.
Variable Speed Pumping
Variable water flow involves inversely changing the water flow through the evaporator as the load changes.
Daikin chillers are designed for this duty provided that the rate of change in water flow is slow and the
minimum and maximum flow rates for the vessel, as shown in Figure 11 on page 18 are not exceeded.
The r
ecommended maximum change in water flow is 10 percent of the allowable flow change per minute. Flow
is usually not reduced below 50 percent of design flow (provided vessel minimum flow rates are not exceeded).
For example, a 150-ton chiller might have chilled water flow of 360 gpm, reduced to 50 percent, would be 180
gpm. However, the minimum flow rate is 216 gpm, so the flow change would be 360 gpm minus 216 gpm, or
144 gpm. This means that the allowable flow rate change would be 10 percent of 144 or 14.4 gpm per minute.
MicroTech II Control
Figure 29, MicroTech II Control Panel
Magnitude chillers are equipped with the Daikin MicroTech II control system consisting of:
• Op
erator interface touchscreen (OITS) with a 15-inch Super VGA color screen.
• Control Panel containing the MicroTech II controller interfacing with the compressor-mounted controls,
the PC controlling the OITS and various switches and field connection terminals.
Operating instructions for the MicroTech II controller are contained in Operating Manual OM 1008.
Use with On-Site Generators
Magnitude chillers (excluding WMC 145S) have their total tonnage divided between two compressors that start
sequentially and they are operated with variable frequency drives. These features make Magnitude chillers
especially appropriate for use in applications where they may be required to run with on-site electrical
generators. This is particularly true when the generators are used for temporary power when the utility power is
lost.
Generator Sizing: Gas and diesel generators are sensitive to the compressor’s locked-rotor characteristics when
the chillers start up. Use the electrical data supplied with the performance output sheet, obtained from the Daikin
sales office, for generator sizing purposes. The chiller data sheet will show the RLA, which is for both
compressors. Refer to Electrical Data to determine the LRA, based on the RLA. It is important to size the
generator to handle the LRA at start up.
S
tarting/Stopping Procedure: The stopping of the chiller in the event of a power failure should be uneventful.
The chiller will sense a loss of voltage and the compressors will stop, coasting down using power generated
from their dynamic braking to maintain the bearing magnetic field. The stop signal will initiate a three-minute
stop-to-start timer, effectively preventing compressor restart for three minutes. The timer is adjustable from three
to fifteen minutes; the recommended default value is three minutes. This interval allows the generator sufficient
time to get up to speed and stabilize. The chiller will restart automatically when the start-to-start timer expires.