Johnson Controls YORK YVAM 0350, Руководство по эксплуатации и техническому обслуживанию

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Table 5: Temperature setpoint
Control source Leaving Chilled Liquid Temperature setpoint
Local
Local Leaving Chilled Liquid Temperature setpoint, entered from the panel. It is
programmable over the range of 38.0°F to 70.0°F (3.3°C to 21.1°C) for water or
10.0°F to 70.0°F (-12.2°C to 21.1°C) for brine. If Smart freeze is enabled, the range
is 36.0°F to 70.0°F (2.2°C to 21.1°C) for water. The default is 45°F (7.2°C).
ISN (BAS)
Remote Leaving Chilled Liquid Temperature setpoint value sent over
communications. The setpoint entered from the panel is ignored. If nothing is
written to the address, the default is 45°F (7.2°C).
Analog remote
Local Leaving Chilled Liquid Temperature setpoint, entered from the panel plus
the temperature offset defined by the remote analog input signal. A remote
device can provide an analog signal (0 mA to 20 mA, 4 mA to 20 mA, 0 VDC to 10
VDC, or 2 VDC to 10 VDC) that creates the temperature offset in Analog Remote
mode. The span of the offset may be defined as 10ºF, 20ºF, 30ºF, or 40ºF (-12.2°C,
-6.7°C, -1.1°C, or 4.4°C) using the Local Leaving Chilled Liquid Temperature Range
setting from the panel. For example, if this Range setpoint is programmed for
10°F (-12.2°C) and the Local Leaving Chilled Liquid Temperature setpoint is 45°F
(7.2°C), then the remote device can set the Leaving Chilled Liquid Temperature
setpoint over the range 45.0ºF to 55.0°F (7.2°C to 12.8°C) as its voltage or current
changes from minimum to maximum.
Digital remote
Local Leaving Chilled Liquid Temperature setpoint, entered from the panel plus
the temperature offset defined by the remote pulse width signal. A remote device
can provide a Pulse Width Modulation (PWM) signal in Digital Remote mode that
creates the temperature offset in Digital Remote mode. The span of the offset
may be defined as 10ºF, 20ºF, 30ºF, or 40ºF (-12.2°C, -6.7°C, -1.1°C, or 4.4°C) using
the Local Leaving Chilled Liquid Temperature Range setting from the panel. For
example, if this Range setpoint is programmed for 10°F (-12.2°C) and the Local
Leaving Chilled Liquid Temperature setpoint is 45°F (7.2°C), then the remote
device can set the Leaving Chilled Liquid Temperature setpoint over the range
45.0ºF to 55.0°F (7.2°C to 12.8°C) as its pulse duration changes from minimum to
maximum. The PWM input is in the form of a 1 to 11 second relay contact closure
that applies 115 VAC to the I/O Board TB4- 19 for 1 to 11 seconds. A contact
closure time (pulse width) of 1 second produces a 0°F (-17.8°C) offset. An 11
second closure produces the maximum offset. The relay contacts should close
for 1 to 11 seconds at least once every 30 minutes to maintain the setpoint to the
preferred value. If a 1 to 11 second closure is not received within 30 minutes of
the last closure, the offset is defaulted to zero. A closure is only accepted at rates
not to exceed once every 70 seconds. Offset (°F) = (pulse width in seconds – 1)
(Local Leaving Chilled Liquid Temperature Range) divided by 10.
Regardless of which method is used to select the preferred Leaving Chilled Liquid Temperature
(LCHLT), the chiller controls to its own Active LCHLT Setpoint. The Active Setpoint is a target to the
programmed setpoint. When the chiller is not running, the Active Setpoint is set to Entering Chilled
Liquid Temperature minus a programmable offset (default 5°F), but not adjusted to less than the
programmed LCHLT setpoint. When the compressor motor starts, the Active LCHLT Setpoint is
ramped from this value to the programmed LCHLT Setpoint at the programmable LCHLT Setpoint
Ramp Rate (default 0.1°F/second). This keeps the chiller from undershooting setpoint excessively
during pulldown. Any time the programmed setpoint is changed during operation, the active
setpoint is ramped to the new value at this rate.
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