York Millennium YCAS 310, Installation Operation & Maintenance

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YORK INTERNATIONAL
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rameters for the automatic lead / lag selection are as
follows:
1. If both compressors in a group are ready to start
and the anti-recycle timers are timed out, the com-
pressor with the lowest run hours will start first. If
run hours are equal, the lower system number will
start first.
2. If both compressors in a group are waiting to start
but the anti-recycle timers are not yet timed out, lead
will be assigned to the compressor with the shortest
anti-recycle time in an effort to provide cooling
quickly.
3. If the lead compressor / group is locked out, faulted
and waiting to restart, has its system switch on the
micro board in the OFF position, or a run permissive
is keeping an individual system from running, the
lag compressor is swapped to the lead. This occurs
whether the lag compressor / group is on or off. See
Section 1.12 and 8.2 for additional details and pro-
gramming.
SWITCH 8: Refrigerant
Open:
The R134a mode MUST be selected for models using
refrigerant R134a. Incorrect selection of this switch may
cause serious damage to the chiller.
Closed:
The R22 mode MUST be selected for models using
refrigerant R22. Incorrect selection of this switch may
cause serious damage to the chiller.
Closed:
Wye-Delta Mode MUST be used for chillers with multi-
contactor and resistor Wye-Delta (Star/Delta) closed
transition starters on each compressor.
SWITCH 7: Compressor Lead/Lag
Open:
Manual Lead / Lag Mode allows selection of the com-
pressor or compressor group lead / lag sequence us-
ing external contact closure.
The manual lead / lag selection is automatically over-
ridden (causing the lag compressor / group to become
the lead) any time the selected lead compressor / group
shuts down due to a lockout, is awaiting restart after a
fault, has its system switch(es) on the Micro Board in
the Off position, or if a run permissive is keeping the
lead system off. This is done to maintain chilled liquid
temperature as close to setpoint as possible. See Sec-
tions 1.12 and 8.3 for additional details & programming.
Closed:
In the Automatic Lead / Lag Mode, lead / lag selection
between compressors and compressor groups is au-
tomatic. In this mode the micro attempts to balance
run time between the compressors / groups. The pa-
W Y E D E L T A
M O T O R S T A R T I N G
M A N U A L
L E A D / L A G
A U T O M A T I C
L E A D / L A G
R E F R I G E R A N T T Y P E
R 1 3 4 A
R E F R I G E R A N T T Y P E
R 2 2