Compressor Operation - Load Limiting - York YCAL0043E Series Installation Operation & Maintenance

Unit Controls
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 lim it ed 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 al low up to 2 com pres sors per system to run, and
the 33% limit would allow only 1 compressor per system
to run. Five-compressor units may be load lim it ed to
40% (1 compressor per system runs) or 80% (up to 2
compressors per system) are permitted to run. No oth er
val ues of lim it ing are avail able.
There are two ways to load limit the unit. The fi rst 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 – Ter mi nals
13 - 21) and PWM inputs (CTB1 – Terminals 13 - 20).
Stage 1 of load lim it ing in volves clos ing the Load Limit
input. Stage 2 of load lim it ing in volves closing both the
Load Limit and PWM in puts. The fi rst stage of lim it ing is
ei ther 80%, 66% or 50%, de pend ing on the num ber of
com pres sors on the unit. The second stage of lim it ing
is either 40% or 33% and is only avail able on 3, 5 & 6
compressor units. Ta ble 31 shows the load lim it ing per-
mit ted for the var i ous num ber of com pres sors.
TABLE 31 – COMPRESSOR OPERATION – LOAD LIMITING
COMPRESSORS IN UNIT
2
3
4
5
6
106
Si mul ta neous operation of Load Lim-
it ing and EMS-PWM Tem per a ture
Reset (de scribed on fol low ing pages)
can not oc cur.
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 nor mal ly-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 – ter mi nals 29 to 30.
Sys tem 2 alarm contacts are located at CTB2 – ter mi nals
31 to 32. The alarm contacts will close when con di tions
al low the unit to operate.
STAGE 1
50%
66%
50%
80%
66%
FORM 150.62-NM7 (103)
STAGE 2
–
33%
–
40%
33%
YORK INTERNATIONAL