Trane IntelliPak SAHL Series, Инструкция по установке, эксплуатации и обслуживанию

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RT-SVX36G-EN 19
General Information
Lead-Lag
Is a selectable mode of operation on 20 thru 130 Ton units within the Human Interface. It alternates
the starting between the first compressor of each refrigeration circuit. On 40 - 89 Ton units only the
compressor banks will switch, not the order the compressors within a bank, providing the first
compressor in each circuit had been activated during the same request for cooling.
Supply and Exhaust/Return Fan Circuit Breakers (with 1CB1 and 1CB2)
The supply fan and exhaust fan motors are protected by circuit breakers 1CB1 and 1CB2
respectively for 208 -230 V applications. They will trip and interrupt the power supply to the motors
if the current exceeds the breaker's “must trip” value. For 460 -575 V applications, fan motors will
be protected with manual motor protectors. The rooftop module (RTM) will shut all system
functions “Off” when an open fan proving switch is detected.
Manual Motor Protectors (380V through 575V Only)
Manual motor protectors will be used as branch circuit protection for compressors and supply fan
motors. These devices are capable of providing both overload and short-circuit protection. Before
operating, the manual motor protector must be switched with the rotary on/off switch to the “ON”
position and the overload setpoint dial must be set to the appropriate rating of the motor.
Important: In order to avoid nuisance trips, the overload setpoint dial must be adjusted to the
following calculated value:
Overload Setting = (Motor FLA)
Overload Setting = (Compressor RLA) x 1.12
Return Plenum Pressure High Limit
The Return Plenum Pressure High Limit Setpoint has a non-adjustable value of 3.5 iwc. When the
return plenum pressure exceeds the Return Plenum Pressure High Limit for more than 1 second,
a “Return Pressure shutdown” signal is sent, and an automatically resetting diagnostic is set. After
the return fan is off, the Return Pressure Shutdown signal is cancelled. The unit will not be allowed
to restart within 15 seconds of shutdown. Three consecutive occurrences of the Return Plenum
Pressure exceeding the Return Plenum Pressure Limit will cause a manual reset diagnostic. The
occurrence counter will be reset every time the unit goes through a reset, transitions from Stop to
Auto, or transitions into and out of Occupied or Unoccupied control.
Low Pressure Control (LPC)
LPC is accomplished using a binary input device. LP cutouts are located on the suction lines near
the scroll compressors. The LPC contacts are designed to close when the suction pressure exceeds
41± 4 psig. If the LP control is open when a compressor is requested to start, none of the
compressors on that circuit will be allowed to operate. They are locked out and a manual reset
diagnostic is initiated.
The LP cutouts are designed to open if the suction pressure approaches 25± 4 psig. If the LP cutout
opens after a compressor has started, all compressors operating on that circuit will be turned off
immediately and will remain off for a minimum of three minutes. If the LP cutout trips four
consecutive times during the first three minutes of operation, the compressors on that circuit will
be locked out and a manual reset diagnostic is initiated.
Saturated Condenser Temperature Sensors (2RT1 and 2RT2)
These analog input devices are mounted inside a temperature well located on a condenser tube
bend. They monitor the saturated refrigerant temperature inside the condenser coil and are
connected to the SCM/MCM (1U49). As the saturated refrigerant temperature varies due to
operating conditions, the condenser fans are cycled “On” or “Off” as required to maintain
acceptable operating pressures. For evaporative condensers, this value is determined by the MPM
which converts a pressure to a temperature value that is sent to the MCM to be used for head
pressure control.