YORK INTERNATIONAL
98
FORM 150.62-NM7 (103)
SYSTEM LEAD/LAG
Lead/lag between systems may be selected to help
equalize average run hours between systems on chill-
ers with 2 refrigerant systems. This may be pro grammed
under the OPTIONS key. Auto lead/lag allows au to mat ic
lead/lag of the two systems based on average run hours
of the compressors in each system. Manual lead/lag
se lects specifi cally the sequence in which the micro
starts systems.
COMPRESSOR LEAD/LAG
The compressors within a system rotate starts in se-
quence 1, 2 or 1, 2, 3 with wraparound. The longest-off
compressor in a system will start fi rst, and the longest-
running compressor in a system will turn off fi rst. When
un load ing, the sys tem with the most com pres sors on,
un loads fi rst. The lag sys tem will shut down a com-
pres sor fi rst when equal num bers of com pres sors are
op er at ing in each sys tem. The micro will not at tempt to
equal ize run time of com pres sors in a system.
Once the second system has started a compressor, the
micro will attempt to equally load each system. Once this
occurs, loading will alternate between systems.
If Soft Start is enabled on European models with this
option, compressor lead/lag will function as outlined in
Option 12 under the Options key.
ANTI-RECYCLE TIMER
The programmable anti-recycle timer assures that sys-
tems do not cycle. This timer is programmable under the
PROGRAM key between 300 - 600 seconds. When ev er
possible, to reduce cycling and motor heating, the anti-
recycle timer should be adjusted to 600 seconds. The
programmable anti-recycle timer starts the timer when
the fi rst compressor in a system starts. The timer begins
to count down. If all of the compressors in a cir cuit cycle
off, a compressor within the circuit will not be permitted to
start until the anti-recycle timer has timed out. If the lead
system has run for less than 5 minutes, 3 times in a row,
the anti-recycle timer will be extended to 10 minutes.
ANTI-COINCIDENCE TIMER
This timer is not present on single-system units. Two
tim ing controls are present in software to assure com-
pres sors within a circuit or between systems, do not start
si mul ta neous ly. The anti-coincidence timer as sures there
is at least a one minute delay between system starts on
2-circuit systems. This timer is NOT pro gram ma ble. The
load timers further assure that there is a minimum time
between compressor starts within a sys tem.
EVAPORATOR PUMP CONTROL
The evaporator pump dry contacts (CTB2 – terminals
23 - 24) are en er gized when any of the fol low ing con-
di tions are true:
Unit Controls
Notes:
1. Step 1 is Hot Gas Bypass and is skipped when loading occurs. Hot Gas Bypass op er a tion is inhibited during Pumpdown.
2. Step 3 is skipped when loading occurs.
3. Step 4 is skipped when unloading occurs.
TABLE 25 – RETURN CHILLED LIQUID CONTROL FOR 4 COMPRESSORS (6 STEPS)
*STEP COMPRESSOR COMPRESSOR ON POINT COMPRESSOR OFF POINT
0 0 SETPOINT SETPOINT
1 1 W/HGB SP + CR/8 (Note 1) SETPOINT
2 1 NO HGB SP + CR/4 SP + CR/8
3 2 SP + 2*CR/4 (Note 2) SP + CR/4
4 2 SP + 2*CR/4 SP + CR/4 (Note 3)
5 3 SP + 3*CR/4 SP + 2*CR/4
6 4 SP + CR SP + 3*CR/4
* STEP can be viewed using the OPER DATA key and scrolling to COOLING DEMAND.
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