FORM 150.44-NM4
73
YORK INTERNATIONAL
Mounted Pump Control Kit is 471-01232-101. This kit
is not required if a second Relay Output Board is al-
ready 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.
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 mi-
croprocessor board is placed in the ON position.
If a daily schedule is programmed, the evaporator wa-
fer pump contacts will transition when the daily sched-
ule 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. 28.
FIG. 28
EVAPORATOR WATER PUMP CONTACT
CONNECTION POINT
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 required if a second Relay Output Board is al-
ready 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
possible. In these cases a low suction pres-
sure shutdowns may sometimes occur, but can
usually be tolerated.
Operation
The fundamental purpose of the Low Ambient Option
is to reduce the capacity of the condenser when the
ambient temperature is in the 0° to 25°F range. This
assures that adequate discharge pressures can be
maintained at low temperatures which will eliminate low
suction pressure faults.
Operation at low ambients is accomplished by cycling
fans according to discharge pressure. This requires the
addition of discharge pressure transducers which al-
lows the microprocessor to add two additional steps of
control to the standard fan control scheme. Fans are
now allowed to cycle completely off and a fan is permit-
ted to run in the reverse direction. This reduces the
capacity of the condenser as required. Reverse rota-
tion of the fans is accomplished by the addition of re-
versing contactors.
Components
The Low Ambient Option consists of 3 kits; 371-01287-
121 Low Ambient Kit, a 471-01262-111 Discharge Pres-
sure Readout Kit, and also a 471-01232-101 Relay
Board Kit. All three kits are required. The Relay Board
Kit is not required if two Relay Boards are already
present in the panel.
When the Low Ambient Option is installed, the follow-
ing physical changes are made to the standard chiller:
1. Discharge pressure transducers and wiring are
added.
2. Reversing contactors 7M with supporting wiring is
added.
3. A second Relay Output Board and wiring is installed.