York YCAL0014SC, YCAL0080SC Unit Controls, Pumpdown Llsv Control, Load Limiting, Alarm Status

Unit Controls

PUMPDOWN (LLSV) CONTROL

Each system has a Pumpdown feature upon shut-off. On a non-safety, non-unit switch shutdown, all compres- sors but one in the system will be shut off. The LLSV will also be turned off. The final compressor will be al- lowed to run until the suction pressure falls below the cutout or for 180 seconds, which ever comes first. Manual pumpdown from the keypad is not possible.

LOAD LIMITING

Load Limiting is a feature that prevents the unit from loading beyond the desired value. 2 and 4 compressor units can be load limited to 50%. This would allow only 1 compressor per system to run. 3 and 6 compressor units can be load limited to 33% or 66%. The 66% limit would allow up to 2 compressors per system to run, and the 33% limit would allow only 1 compressor per system to run. No other values of limiting are available.

There are two ways to load limit the unit. The first is through remote communication via an ISN.

A second way to load limit the unit is through closing contacts connected to the Load Limit (CTB1-Terminals 13-21) and PWM inputs (CTB1-Terminals 13-20). Stage 1 of load limiting involves closing the Load Limit input. Stage 2 of load limiting involves closing both the Load Limit and PWM inputs. The first stage of limiting is ei- ther 66% or 50%, depending on the number of com- pressors on the unit. The second stage of limiting is 33% and is only available on 3 and 6 compressor units.

Table 43 shows the load limiting permitted for the vari- ous number of compressors.

NOTE: Simultaneous operation of Load Limiting and EMS-PWM Temperature Reset (described on following pages) cannot occur.

COMPRESSOR RUN STATUS

Compressor run status is indicated by closure of con- tacts at CTB2 – terminals 25 to 26 for system 1 and CTB2 – terminals 27 to 28 for system 2.

ALARM STATUS

System or unit shutdown is indicated by normally-open alarm contacts opening whenever the unit shuts down on a unit fault, or locks out on a system fault. System 1 alarm contacts are located at CTB2 - terminals 29 to

30.System 2 alarm contacts are located at CTB2 - ter- minals 31 to 32. The alarm contacts will close when conditions allow the unit to operate.

COMPRESSOR SEQUENCING

The unit control will attempt to equalize the total run hours on individual compressors within a system. When a system is about to start, the compressor with the least run time in that system will be the first to start. When the system has to load, the next compressor to start will be the one with the least run time that is currently not running in that system.

TABLE 43 – COMPRESSOR OPERATION – LOAD LIMITING

COMPRESSORS IN UNIT	STAGE 1	STAGE 2
2	50%	–
3	66%	33%
4	50%	–
6	66%	33%

92 YORK INTERNATIONAL