Daikin Magnitude WME106CD User Manual

InsTallaTIon
www.DaikinApplied.com 19 IOM 1266-2 • MAGNITUDE
®
MODEL WME CHILLERS
CAUTION
When common piping is used for both building heating and
cooling modes, care must be taken to provide that water
owing through the evaporator cannot exceed 115°F (46°C).
Water this hot can damage controls or cause the relief valve
to discharge refrigerant.
Condenser Water
Temperature Control
Condenser water control is an important consideration in chiller
plant design since condenser water temperature will directly
impact chiller operation and efciency. When the ambient
wet bulb temperature is lower than peak design, the entering
condenser water temperature from the cooling tower can
be allowed to fall, improving chiller performance. However,
operational issues may occur when the condenser water
temperatures are either too high or too low. The WME chiller
provides several options to assist the chiller plant designer in
providing the optimum control of condenser water temperature.
Cooling Tower Control
Control of the cooling tower is required to maintain stability and
avoid operational issues. This can be achieved through a BAS
or by using the MicroTech
®
controller. For systems utilizing a
common condenser water loop for multiple purposes, the BAS
contractor must provide the control but use of the MicroTech
®
output signal is still recommended.
The preferred cooling tower control utilizes a variable speed
fan. MicroTech
®
will provide a control signal to determine the
proper fan speed. It can also control up to two stages of fan
cycling. Note that fan cycling can cause cooling tower water
temperature to uctuate as fans stage on/off, potentially adding
instability to the system.
Each of the following acceptable methods can be
controlled by the MicroTech
®
or through a BAS utilizing
the MicroTech
®
output signals:
1. Three-Way Bypass Valve Operation
A traditional method for building condenser pressure at
startup with colder condenser water is with the use of
a three-way bypass valve. The device blends warmer
water leaving the condenser with cooler water from the
cooling tower at the condenser inlet. The bypass valve
position will change until full ow from the tower to the
condenser is obtained. The MicroTech
®
provides only
the valve position control signal. Main power to drive the
valve’s actuator must be provided by the installer. The
three-way valve should be located close to the chiller
within the equipment room to minimize the volume of
water.
2. Two-Way Valve Operation
Another condenser control method is to use a modulating
two-way control valve located on the outlet connection of
the condenser. The valve will be nearly closed at startup
to restrict water ow, which keeps generated heat in
the condenser until an acceptable minimum condenser
pressure is reached. As heat builds, the valve will open
slowly until a full ow condition from the cooling tower
is established. A separate power source is required to
provide power to the valve actuator.
NOTE: To ensure proper operation, caution should be
used when utilizing the two-way valve option.
3. VFD Operating with a Condenser Water Pump
A third method of condenser control for startup is
utilizing a variable frequency drive with the condenser
water pump. The speed will change as directed by the
MicroTech
®
output signal until design ow is reached.
Speed adjustments may be required during the initial
chiller startup as determined by the service technician.
NOTE: Not using the MicroTech
®
logic to control valves
and variable frequency drives may result in system
instability and capacity reduction.
Condenser Pump Sequencing
It is recommended to utilize the logic built into the MicroTech
®
controller to start the condenser pump. MicroTech
®
has the
capability to operate a primary pump and a secondary standby
pump. The condenser water ow should be stopped when
the chiller shuts off. This will conserve energy and prevent
refrigerant from migrating to the condenser. Moisture in the
air can condense on the cooler surfaces of the un-insulated
condenser barrel if ow is present when the chiller is idle.
Water Side Economizer Cycle Operation
The WME-C vintage chiller is capable of inverted duty
operation, meaning the chiller has the capability to accept
entering condenser water lower than the leaving evaporator
water temperature. In doing so, it extends the range of
applications of the chiller and can eliminate the waterside
economizer from the system.
The savings resulting on the inverted operation can be
quantied with the elimination of the waterside economizer,
while also retaining the ability of the chiller to address cooling
needs during low ambient temperatures. ASHRAE 90.1
prescribes to include a waterside economizer; so when it is
removed, a performance-based compliance path using energy
modeling must be followed in order to conrm compliance to
the code.
If it is conrmed that a waterside economizer is benecial to
a particular system, the BAS contractor will need to provide
controls for the heat exchanger including isolation valves and
temperature control. The BAS contractor will also need to
control the isolation valves for the chiller. It is important to use
slow-acting type valves to prevent rapid changes in system
ows. Changeover from economizer cooling to mechanical
cooling requires one of the methods previously mentioned to
maintain suitable condenser head pressure.
Contact your local Daikin Applied representative for more
information on this application.

Daikin Magnitude WME106CD Specifications

General

Brand	Daikin
Model	Magnitude WME106CD
Category	Chiller
Language	English