York YCUL0045E, Установка, эксплуатация и обслуживание

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JOHNSON CONTROLS
88
FORM 150.63-NM8 (1020)
UNIT CONTROLS
SUCTION PRESSURE CONTROL
The setpoint in Suction Pressure Control is the suction
pressures each individual system on the condensing unit
will control to /- the cooling range. The Setpoint
High Limit is the Setpoint plus the Cooling Range. The
Setpoint Low Limit is the Setpoint minus the Cooling
Range. Each system is controlled independently of each
other according to its setpoint and cooling range.
Each system must have its own zone thermostat. If the
respective zone thermostat is closed, the lead compres-
sor on that system will be energized. In addition the
liquid line solenoid to that system will be energized.
Upon energizing any compressor the 60 second Anti-
Coincidence timer will be initiated.
If after 150 seconds of run-time the suction pressure is
still above the Setpoint High Limit, the next compres-
sor in sequence will be energized. Additional loading
stages are energized at a rate of once every 150 seconds
if the suction pressure remains above the Setpoint High
Limit. Each system will have its own load timer of 150
seconds.
If the suction pressure falls below the Setpoint High
Limit and greater than the Setpoint Low Limit, loading
and unloading do not occur. This area of control is called
the control range.
If the suction pressure falls below the Setpoint Low
Limit, unloading (compressors cycling off) occurs at
a rate of 30 seconds per system. The zone thermostat
must be satisfied before the last compressor in the sys -
tem cycles off, even if the suction pressure is below the
Setpoint Low Limit.
Hot Gas Bypass solenoid will be energized as the last
stage of unloading. If the zone thermostat calls for cool-
ing when the suction pressure is below the Setpoint Low
Limit, the first stage compressor will be energized with
the hot gas solenoid.
It should be noted that the zone thermostat has ultimate
control. As long as the zone thermostat is calling for
cooling, at least compressor will be running, regardless
of whether the suction pressure is below Setpoint Low
Limit.
Figure 12 illustrates loading and unloading in Suction
Pressure Control Mode.
Refer to section on Setpoints
Keys for programmable values.
FIG. 12 – SUCTION PRESSURE CONTROL
30 second control range 150 second
unloading (no compressor staging) loading
67 PSIG (4.6 BAR) 73 PSIG (5.0 BAR)
Setpoint
70 PSIG (4.8 BAR)
Setpoint = 70 PSIG (4.8 BAR)
Control Range = 3 PSIG ( 20.7 kPa)
Setpoint
Low Limit
Setpoint
High Limit