JOHNSON CONTROLS
19
SECTION 3 - SYSTEM COMPONENTS DESCRIPTION
FORM 160.76-O1
ISSUE DATE: 6/15/2015
3
OIL HEATER
During long idle periods, the oil in the compressor oil
reservoir tends to absorb as much refrigerant as it can
hold, depending upon the temperature of the oil and
the pressure in the reservoir. As the oil temperature is
lowered, the amount of refrigerant absorbed will be
increased. If the quantity of refrigerant in the oil be-
comes excessive, violent oil foaming will result as the
pressure within the system is lowered on starting. This
foaming is caused by refrigerant boiling out of the oil
as the pressure is lowered. If this foam reaches the oil
pump suction, the bearing oil pressure will fluctuate
with possible temporary loss of lubrication, causing the
oil pressure safety cutout to actuate and stop the sys-
tem. Refer to
Optiview™ Control Center – Operation
and Maintenance (Form 160.54-O1)
.
MOTOR DRIVELINE
The compressor motor is an open-drip-proof, squir-
rel cage, induction type constructed to YORK design
specifications. 60 hertz motors operate at 3570 rpm. 50
hertz motors operate at 2975 rpm.
The open motor is provided with a D-flange, cast iron
adapter mounted to the compressor and supported by a
motor support.
Motor drive shaft is directly connected to the compres-
sor shaft with a flexible disc coupling. This coupling
has all metal construction with no wearing parts to as-
sure long life, and no lubrication requirements to pro-
vide low maintenance.
For units utilizing remote Electro-Mechanical starters,
a terminal box is provided for field connected conduit.
Motor terminals are brought through the motor cas-
ing into the terminal box. Jumpers are furnished for
three-lead type of starting. Motor terminal lugs are not
furnished. Overload/over current transformers are fur-
nished with all units.
HEAT EXCHANGERS
Evaporator and condenser shells are fabricated from
rolled carbon steel plates with fusion welded seams.
Heat exchanger tubes are internally enhanced type.
The evaporator is a shell and tube type with customer
process fluid flowing inside the tubes and refrigerant
removing heat on the shell side via evaporation. Evap-
orator codes 2*, 4*, 6* utilize a hybrid falling film de-
sign. It contains a balance of falling film technology
to optimize efficiency, minimize refrigerant charge,
and maintain reliable control. A specifically designed
spray distributor provides uniform distribution of re-
frigerant over the entire length to yield optimum heat
transfer. The hybrid falling film evaporator design has
suction baffles around the sides and above the falling
film section to prevent liquid refrigerant carryover into
the compressor.
A 1-1/2" (38 mm) liquid level sight glass is conve-
niently located on the side of the shell to aid in deter-
mining proper refrigerant charge. The evaporator shell
contains a dual refrigerant relief valve arrangement set
at 235 psig (16.2 barg) on Q compressor models; or
single-relief valve arrangement, if the chiller is sup-
plied with optional refrigerant isolation valves. A 1"
(25.4 mm) refrigerant charging valve is provided. The
condenser is a shell and tube type, with a discharge
gas baffle to prevent direct high velocity impingement
on the tubes. The baffle is also used to distribute the
refrigerant gas flow properly for most efficient heat
transfer. An integral sub-cooler is located at the bottom
of the condenser shell providing highly effective liquid
refrigerant subcooling to provide the highest cycle ef-
ficiency. The condenser contains dual refrigerant relief
valves set at 235 psig (16.2 barg).
The removable waterboxes are fabricated of steel. The
design working pressure is 150 psig (10.3 barg) and
the boxes are tested at 225 psig (15.5 barg). Integral
steel water baffles are located and welded within the
waterbox to provide the required pass arrangements.
Stub-out water nozzle connections with ANSI/AWWA
C-606 grooves are welded to the waterboxes. These
nozzle connections are suitable for ANSI/AWWA
C-606 couplings, welding or flanges, and are capped
for shipment. Plugged 3/4" (19 mm) drain and vent
connections are provided in each waterbox.
REFRIGERANT FLOW CONTROL
Refrigerant flow to the evaporator is controlled by a
variable orifice.
A level sensor senses the refrigerant level in the con-
denser and outputs an analog voltage to the Microboard
that represents this level (0% = empty; 100% = full).
Under program control, the Microboard modulates a
variable orifice to control the condenser refrigerant
level to a programmed setpoint. Other setpoints affect
the control sensitivity and response. These setpoints
must be entered at chiller commissioning by a qualified
service technician. Only a qualified service technician
may modify these settings.
