FORM 150.75-NM2
71
YORK INTERNATIONAL
UNIT ON/OFF SWITCH
A master UNIT ON/OFF switch is located on the key-
pad. This rocker switch allows the operator to turn the
entire chiller OFF if desired. The switch must be placed
in the ON position for the chiller to operate.
Whenever the switch is placed in the OFF position, a
STATUS display indicating the condition will be dis-
played. This message is shown below.
SYSTEM SWITCHES
SYSTEM SWITCHES 1-4 are located on each Micro-
processor Board (See Fig. 31). These allow the operator
to selectively turn a given system on or off as desired.
On a 4 system chiller, switches 1, 2, 3 & 4 of the Master
Microprocessor Board MUST be ON to allow operation
of all 4 compressors. This allows operator control of all 4
systems from the Master Microprocessor Board.
Switches 1 & 2 on the Slave Microprocessor Board MUST
also be ON to enable operation of compressors 3 & 4
which is controlled by the Slave Microprocessor. If these
two switches are not ON, the Slave Micro will not re-
spond to commands from the Master to operate com-
pressors 3 & 4 Additionally, switches 3 & 4 of the Slave
Microprocessor Board should be in the OFF position.
Whenever a switch is placed in the OFF position, a STA-
TUS display indicating the condition will be displayed
indicating that the system does not have a Run Permis-
sive signal. A sample of this message follows:
NOTE: This message will not appear if Anti-recycle or
Anti-coincident timers are in effect and are be-
ing displayed.
ALARM CONTACTS (ANNUNCIATION ALARM)
Dry contacts connected to terminals 23 and 24 (Fig.
32) are supplied on the Master Control Panel, which
will transition to function as a warning whenever a fault
shutdown occurs on any system or if power is lost to
the control panel. The dry contacts are normally open
(N.O.) and will close when control power is applied to
the panel, if no fault conditions are present. If power is
lost or a fault lockout occurs, the contact will open.
A 28VDC or 120VAC external alarm circuit (by others)
may be wired into the YORK supplied alarm contacts.
Any inductive load devices (relay, contactor), supplied
by the user which are connected to the dry contacts,
MUST be suppressed at the load. Use YORK P/N 031-
00808-000 suppressor (not supplied). Failure to do this
will result in nuisance faults and possible damage to the
chiller.
CAUTION: If the alarm circuit is applied in an applica-
tion used for critical duty (such as process
duty or cooling other critical equipment) and
26572A
UNIT ON/OFF SWITCH
U N I T
S W I T C H
I S
I N
T H E
O F F
P O S I T I O N
S Y S # 1
N O
R U N
P E R M
S Y S # 2
N O
R U N
P E R M
UNIT
ON/OFF
SWITCH