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

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RT-SVX36G-EN 93
Unit Start Up
Cooling Sequence of Operation
Time delays are built into the controls to increase reliability and performance by protecting the
compressors and maximizing unit efficiency.
Compressor Crankcase Heaters
Each compressor is equipped with a crankcase heater controlled by a 600 volt auxiliary switch on
the compressor contactor. The proper operation of the crankcase heater is important to maintain
an elevated compressor oil temperature during the “Off” cycle to reduce oil foaming during
compressor starts.
When the compressor starts, the sudden reduction in crankcase pressure causes the liquid
refrigerant to boil rapidly causing the oil to foam. This condition could damage compressor
bearings due to reduced lubrication and could cause compressor mechanical failures.
When power has been “Off” for an extended period, allow the crankcase heater to operate a
minimum of 24 hours before starting the unit.
SZVAV Cooling Sequence of Operation
Single Zone VAV units will be equipped with a VFD controlled supply fan which will be controlled
via the 0-10VDC RTM VFD output and the RTM Supply Fan output. With the RTM Supply Fan output
energized and the RTM VFD output at 0Vdc the fan speed output is 37% (22Hz) from the VFD motor,
by default, and at 10VDC the Fan Speed output is 100% (60Hz). The control scales the 0-10Vdc VFD
output from the RTM linearly to control between the 37%-100% controllable range.
If the RTM determines that there is a need for active cooling capacity in order to meet the calculated
Temperature Setpoint (Tset), the unit will begin to stage compressors accordingly once supply fan
proving has been made. Note that the compressor staging order will be based on unit configuration
and compressor lead/lag status.
Once the Tset calculation has reached its bottom limit (Tset Lower Limit Setpoint) and compressors
are being utilized to meet the demand, the Tset value continues to calculate below the Tset Lower
Limit Setpoint and the algorithm will begin to ramp the Supply Fan Speed up toward 100%. Note
that the supply fan speed will remain at the compressor stage’s associated minimum value (as
described below) until the Tset value is calculated below the Tset Lower Limit Setpoint.
As the cooling load in the zone decreases the zone cooling algorithm will reduce the speed of the
fan down to minimum per compressor stage and control the compressor outputs accordingly. As
the compressors begin to de-energize, the Supply Fan speed will fall back to the Cooling Stage’s
associated minimum fan speed, but not below. As the load in the zone continues to drop cooling
capacity will be reduced in order to maintain the discharge air within the ± ½ Tset deadband.
Cooling Stages Minimum Fan Speed
As the unit begins to stage compressors to meet the cooling demand, the following minimum
Supply Fan Speeds will be utilized for each corresponding Cooling Stage. Note that the Supply Fan
Speed will be allowed to ramp up beyond 37% as determined by the active Tset calculation; the
speeds below are only the minimum speeds per cooling stage. Note that when transitioning
between active cooling stages, compressors may energize prior to the supply fan reaching the
minimum speed for the associated step.
NOTICE:
Compressor Failure!
Unit must be powered and crankcase heaters energized at least 8 hours BEFORE compressors
are started. This will protect the compressors from premature failure.