Alarms; Run Status (Chiller); Lead / Lag Compressor Selection - York YCAS Installation Operation & Maintenance

1.19

ALARMS

Internal contacts are provided in the Micro Panel (See
Section 1.12) which can be used to remotely signal a
warn ing whenever a fault lock out occurs on any sys tem
or if power is lost to the con trol panel. The internal
con tacts are normally open (N.O.) and will close when
con trol power is applied to the pan el, if no fault con di -
tions are present. When a fault occurs which locks out
a system, the respective contacts open. If chiller power
is lost or a unit fault oc curs, such as a Low Water Temp
fault, con tacts for all sys tems will open.
Contacts for SYS 1 are located on the bottom right of
the microprocessor panel, terminals 23 and 24. SYS
2 contacts are located on terminals 27 and 28, SYS 3
on terminals 37 and 38, and SYS 4 on terminals 41
and 42. See Fig. 11, Page 36 for the lo ca tion of these
ter mi nals.
A 28VDC or 120VAC (60 Hz models) or up to 240VAC
(50 Hz models) external alarm circuit (supplied by oth-
ers) may be connected to these contacts. The contacts
are rated at 125VA.
If any inductive load devices (relay or
contactor) sup plied by the user are in
the elec tri cal cir cuit con nect ed to the
dry alarm contacts, the de vice must
be sup pressed at the load with a RC
sup pres sor YORK Part Num ber 031-
00808-000 across the in duc tive coil.
Fail ure to in stall sup pres sors will
result in nui sance faults and pos si ble
damage to the chill er.
If the alarm circuit is applied in an
ap pli ca tion used for critical duty (such
as pro cess duty or cool ing oth er crit-
i cal equip ment) and the alarm cir cuit
should fail to func tion, YORK will not
be li a ble for dam ag es.
1.20

RUN STATUS (CHILLER)

Internal Chiller Run Status contacts between Ter mi nal
28 and 29 close whenever one of the systems is run-
ning. These contacts are lo cat ed on the bottom right of
the Mi cro pro ces sor Board and are rated (voltage and
current) the same as the alarm contacts (Section 1.19).
Also use a suppressor, same as alarm contacts (Section
1.19). In di vid u al system "Run Status" contacts are not
available.
YORK INTERNATIONAL
1.21

LEAD / LAG COMPRESSOR SELECTION

The chiller may be set up for AUTO or MANUAL Lead
/ Lag. This is accomplished by programming the op tion
under the Program Key. Details for programming the
Manual/Auto Lead/Lag Selection are discussed in Pro-
gram Key Section 8.
When AUTO Lead/Lag is utilized, the micro attempts
to balance run time between the two compressors. A
number of conditions can occur which will prevent this
from happening. Factors determining lead/lag se lec tion
and the resulting lead/lag determination are:
1. The micro automatically defaults the lead to SYS 1
and the lag to SYS 2 if both compressors are ready
to start (Anti-recycle Timers timed out) and com-
pres sors have equal run time.
2. In YCAS 3 System models, SYS 2 is assigned fi rst
lag and SYS 3 the second lag. The same lead/lag
assignment occurs with YCAS 4 System models
with SYS 4 as signed as the third lag. Individual
system run sta tus is not present.
3. If all compressors are ready to start (Anti-recycle
timers timed out), the compressor with the lowest
run hours will start fi rst.
4. If all compressors are waiting to start (Anti-re cy cle
timers have not timed out), the micro will assign the
lead to the compressor with the shortest anti-recycle
time in a an effort to provide cooling quick ly.
5. If the lead compressor is locked out, faulted and
waiting to restart, SYS switch on the microboard
is off, or a run permissive is keeping an individual
sys tem from running, the lag (fi rst lag in YCAS 3
Sys tem and YCAS 4 System models) compressor
is swapped to the lead. This is true regardless of
whether the lag compressor is ON or OFF.
MANUAL Lead/Lag selection will be automatically
overridden by the micro to allow the lag compressor to
automatically become the lead anytime the selected lead
compressor shuts down due to a lock-out, lead system
faults and is waiting to restart, system switch on the mi-
cro board is in the OFF position, or if a run permissive is
keeping the lead of the system off. Automatic switchover
in MANUAL mode is provided to try to maintain chilled
liquid temperature as close to setpoint as possible.
FORM 201.19-NM6 (804)
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