York YCAS0130 - Manual (Page 133)

133 YORK INTERNATIONAL
FORM 201.19-NM1 (204)
low suction pres sure cutout setting or for 180 seconds,
whichever comes fi rst. Pump down occurs on “normal”
shut downs where cool ing demand has been satisfi ed or
when a system switch is turned off, a fl ow switch opens,
run per mis sive is lost or a Daily Schedule or a Remote
Shut down is called for.
No pumpdown will occur on a safety shutdown. See
page 138 for the pumpdown display message.
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. See Fig. 11,
Page 38 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.
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
un der the Program Key. Details for programming the
Man u al/Auto Lead/Lag Selection are discussed in Pro-
gram Key Section 8, page 169.
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. If all compressors are ready to start (Anti-recycle
tim ers timed out), the compressor with the lowest
run hours will start fi rst.
3. 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-re cy cle
time in a an effort to provide cooling quick ly.
4. 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 compressor is swapped
to the lead. This is true regardless of whether the
lag compressor is ON or OFF.
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