76
YORK INTERNATIONAL
FIG. 29
CONDENSER WATER PUMP CONTACT
CONNECTION POINT
LD02097
LD02098
FIG. 30
CONDENSER WATER PUMP CONTACT
CONNECTION POINT
EVAPORATOR WATER PUMP CONTACT OPTION
This option provides a dry contact which can be used
to turn on the evaporator water pump. The contact will
be closed by the micro before the micro brings a com-
pressor on. The micro will not bring a compressor on
until a RUN PERMISSIVE signal is established by a
flow switch contact closure. If no daily schedule is set
(all times = 00.00), the evaporator water pump contact
will transition as soon as a System Switch on the micro-
processor board is placed in the ON position.
If a daily schedule is programmed, the evaporator water
pump contacts will transition when the daily schedule
dictates.
If MANUAL OVERRIDE is selected, the evaporator wa-
ter pump contacts will immediately transition.
Connections to this contact can be made on Terminals
25 and 26 of TB1 in the power panel. The location of
these terminals is shown in Fig. 30.
If a power failure occurs which shuts the entire chiller
down, the contacts will not be allowed to close again
until 30 seconds after power is restored. This prevents
rapid cycling of the chilled water pump.
This option utilizes a second Relay Output Board and
associated wiring. The part number for the Field Mounted
Pump Control Kit is 471-01232-101. This kit is not re-
quired if a second Relay Output Board is already installed.
NOTE: Any inductive devices (contactor/relay coil) con-
nected to these contacts must be suppressed
with YORK P/N 031-00808 supplied by others.
Otherwise, nuisance faults may occur.
0°F LOW AMBIENT OPTION
The standard chiller is designed to operate in an ambi-
ent of 25°F or higher. If it is necessary to operate the
chiller in an ambient between 0° and 25°F, the chiller
should be purchased with the factory installed Low Am-
bient Option.
NOTE: Occasional operation below 0°F is normally pos-
sible. In these cases a low suction pressure
shutdowns may sometimes occur, but can usu-
ally be tolerated.
Operation
The fundamental purpose of the Low Ambient Option is
to reduce the capacity of the condenser when the am-
bient temperature is in the 0° to 25°F range. This as-
sures that adequate discharge pressures can be main-
tained at low temperatures which will eliminate low suc-
tion pressure faults.
Operation at low ambients is accomplished by cycling
fans according to discharge pressure. This requires the
addition of discharge pressure transducers which allows
the microprocessor to add two additional steps of con-
trol to the standard fan control scheme. Fans are now
allowed to cycle completely off and a fan is permitted to
run in the reverse direction. This reduces the capacity of
the condenser as required. Reverse rotation of the fans
is accomplished by the addition of reversing contactors.