YORK INTERNATIONAL
74
1.10 COMPRESSOR HEATER
The Compressor Heater in each compressor will be ON
for the first five minutes after the compressor is shut
down. Then the heater is controlled by discharge tem-
perature. If the heater is ON and the discharge tem-
perature rises above 170°F, it will shut off. If the heater
is OFF and the discharge temperature falls below 100°F,
it will turn ON. The heater is controlled by the micropro-
cessor.
The purpose of the heater is to prevent the migration of
refrigerant into the compressor during shutdown, as-
suring proper lubrication of the compressor on start-up.
Anytime power is removed from the chiller for more than
an hour, 115VAC control power should be reapplied to
allow the compressor heaters to remain on for 24 hours
prior to restart.
1.11 EVAPORATOR HEATER
The evaporator heater prevents water standing in the
evaporator from freezing. Whenever the outdoor ambi-
ent temperature drops below 40°F, the microprocessor
will turn the evaporator heaters ON. If temperature rises
above 45°F, the heater will be turned off.
1.12 LEAD LAG COMPRESSOR SELECTION
2 Compressor Lead/Lag Compressor Selection
The chiller may be set up for AUTO or MANUAL Lead/
Lag. This is accomplished by properly configuring the
S1 Dip Switches on the Microprocessor Board. Details
for configuring the switches are discussed in the Dis-
play Key Section under OPTIONS key.
When AUTO Lead/Lag is utilized, the micro attempts to
balance run time between the two compressors. A num-
ber of conditions can occur which will prevent this from
happening. Factors determining lead/lag selection and
the resulting lead/lag determination are discussed below:
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 compres-
sors have equal run time.
2. If both compressors are ready to start (Anti-recycle
Timers timed out), the compressor with the lowest
run hours will start first.
3. If both compressors are waiting to start (Anti-recycle
Timers are not timed out), the micro will assign the
lead to the compressor with the shortest anti-recycle
time in an effort to provide cooling quickly.
4. If the lead compressor is locked out, faulted and
waiting to restart, SYS switch on the micro boards 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.
If MANUAL Lead/Lag is selected, an external dry con-
tact (switch) must be wired into the chiller. This contact
is field supplied. With the contact open, SYS 1 is placed
in the lead. When the contact is closed, SYS 2 will be
lead system.
MANUAL Lead/Lag selection will be automatically over-
ridden by the micro to allow the lag compressor to auto-
matically become the lead anytime the selected lead
compressor shuts down due to a lock-out, lead system
faults and is waiting to restart, lead system switch on
the micro board is in the OFF position, or if a run per-
missive is keeping the lead of the system off. Automatic
switchover in the MANUAL mode is provided to try to
maintain chilled liquid temperature as close to setpoint
as possible.
The dry contact for manual lead/lag selection is wired
into terminals 13 and 19 of the TB4 Terminal Block.
The location of these contacts is shown in Fig. 41.
FIG. 41
TB4 LOCATION MANUAL LEAD LAG
(SEE PAGE 72)
27962A
TB4
Содержание Millennium YDAS 410
Страница 135: ...FORM 201 10 NM4 135 YORK INTERNATIONAL ...