York YCUL0045E, Установка, эксплуатация и обслуживание

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JOHNSON CONTROLS
93
FORM 150.63-NM8 (1020)
2
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 compres-
sor 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. Five-compressor units may be load
limited to 40% (1 compressor per system runs) or 80%
(up to 2 compressors per system) are permitted 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 either 80%, 66% or 50%, depending on the number
of compressors on the unit. The second stage of limit-
ing is either 40% or 33% and is only available on 3, 5
& 6 compressor units. Table 25 shows the load limiting
permitted for the various number of compressors.
Simultaneous operation of Load Lim -
iting and EMS-PWM Temperature
Reset (described on following pages)
cannot occur.
COMPRESSOR RUN STATUS
Compressor run status is indicated by closure of contacts
at CTB2 – terminals 25 to 26 for system 1 and CTB2
– terminals 27 to 28 for system 2. The respective con-
tact will close anytime a compressor is running in that
particular system.
The compressor Run Status contacts can also be used
to cycle the evaporator fan contactor with the compres-
sors.
ALARM STATUS
System or unit shutdown is indicated by normally-open
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 - terminals 31 to
32. The alarm contacts will close when conditions allow
the unit to operate.
TABLE 25 – COMPRESSOR OPERATION – LOAD LIMITING
COMPRESSORS IN UNIT STAGE 1 STAGE 2
2 50% –
3 66% 33%
4 50% –
5 80% 40%
6 66% 33%