Direct Pressure Control; Inlet Temperature Control; Variable Primary Flow; Power Wiring - York YGWH 115 Installation, Commissioning & Operation

Form 6S6I-B01C-EOMA-EN (0318)

Direct Pressure Control

With YGWH units it is possible, if desired, to control the
condenser cooling liquid inlet temperature/flow directly
from the unit refrigerant pressure. The refrigerant
pressure can either be used to control cooling tower
effectiveness by controlling fans or dampers on the
tower, or to control condenser water flow using a three
way bypass valve. The purpose of this method is to
keep a low and steady discharge pressure .But with the
units using R134a refrigerant, it is essential that the
discharge pressure should be higher than suction
pressure for more than 3 bar. 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.
Pump
Condenser
Bypass Loop
Condenser
Pump
Cycling Loop
4-6
Cooling
Tower
3-way
Valve
Cooling
Tower
3-way
Valve

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°C to 24°C 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
diagram above. 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°C to
24°C.

Variable Primary Flow

Johnson Controls recommends a maximum 10%
per minute flow rate change, based on design flow,
for variable primary applications. Provide 8 to 10
gallons per chiller ton (8.6 to 10.8 litres 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 your Johnson Controls Sales Office for more
information for YGWH chillers.

Power Wiring

The allowable variation range of power supply voltage
is ±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 overload protection
(current) for input power supply to the unit.
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 / 400 V / 415 V, 3P
/ 50Hz power supply to the unit with circuit protection.
Connect the power supply to the circuit breaker
located in the power panel on site. Refer to customer
connection diagram.
EN