Johnson Controls YEWS Series, Installation, Operation And Maintanance Instructions

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refrigerant, it is essential that the discharge pressure
should be higher than suction pressure for more than
3Bar.In that case, units should be controlled by a certain
setpoint higher than suction pressure or be controlled by
the suction pressure and a pressure difference.However,
the temperature and flow rate of cooling water should not
exceeds the allowable range.
Inlet Temperature Control
For a cooling tower system the simplest forms of control
is to use fan cycling, fan speed control, or air damper
control, with the tower having a thermostat in its sump.
This will ensure stable condenser cooling liquid
temperature and should be adjusted to ensure a condenser
cooling liquid entering temperature of not lower than
21
℃
to 24
℃
at lower ambient conditions.
If these methods are not available, or a cooling tower is
not the source of cooling water, then a three way valve
recirculation system can be used with control based on
condenser inlet liquid temperature as shown in the upward
diagram. In this case the objective is to maintain the inlet
cooling liquid temperature as low as possible, although
still observing the minimum limit of 21
℃
to 24
℃
.
4.11 Variable Primary Flow
Johnson Controls recommends a maximum 10% per
minute flow rate change, based on design flow, for
variable primary applications. Provide 8-10 gallons per
chiller ton (8.6-10.8 liter per cooling KW) system water
volume. Insufficient system volume and rapid flow
changes can cause control problems or chiller shutdowns.
There are many other design issues to evaluate with
variable primary flow systems. Consult the Johnson
Controls Sales Office for more information about
successfully applying YEWS chillers.
4.12 Power Wiring
The allowable variation range of power supply voltage
equal to the rated voltage value
±
10
％
.
All electrical wiring should be carried out in accordance
with local regulations.
In accordance with China National Standard it is the
responsibility of the user to install current overload
protection for input power supplies of York units.
All sources of supply to the unit must be taken via a
common point of isolation (not supplied by York).
Single Point Power Supply Wiring
Models require field provided 380V(400V/415V)/3P / 50Hz
power supply to the unit with circuit protection. Connecting
power supply to the terminal block located in the power
panel on site.
4.13 Control panel Wiring
The power connect to the I/O switch input terminal is
12VDC while the power connect to the I/O switch output
terminal is 220VAC.
The wiring with 220VAC power must use the dry-contact (It
is suggested to use the golden contact).If the dry-contact is
part of a relay or a contactor, a capacitance-resistance
suppresser winding must be used to restrain the
Electromagnetic Interference.Make sure that the above
precautions are followed to avoid the Electromagnetic
Interference, which may result in the fault or damages on the
unit or the controller.
The length of cable connected to these terminals should not
exceed 7.5 meters.
4.14 220VAC Output
Water pump starter
When the terminal 21 send out a 220VAC power, the water
pump should be started.So the opening and stopping control
of pump can be achieved by contactor and start/stop
program.
Note: Power load should not exeed 5w.
Alarming contract
When the terminal 26 send out a 220VAC signal, the unit
should be in the alarming status.
Note: Power load should not exeed 5w.
4.15 System input
Flow switch
A suitable water flow switch must be connected to terminals
1 and 13 to provide adequate protection against loss of liquid
flow.
Note: Contact Resistance <5
Ω
.
Remote Run/Stop
Connect a remote switch between 8 and 13 to provide remote
start/stop if required.
Note: Contact Resistance <5w.
YEWS-E Water Cooling Screw Chiller/Heat Pump
17