J&E Hall JEHSD-0600-M-3, Техническое руководство

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Issue: 01.05.2017 Page 20
Commissioning
Compressor Operation
The compressor(s) operate in accordance to the suction pressure setpoint which is programmed into the
controller. There is a differential pressure setting both above and below the setpoint. This allows
stable operation of the compressors without constantly switching on & off due to small variations in
suction pressure. This range is known as the Neutral Zone. When the compressor(s) are operating
within this zone, there will be no change to capacity status (i.e. no compressor switched on/off or
additional loading/unloading of variable capacity compressor).
Once the suction pressure goes outside the Neutral Zone, then the controller reacts by increasing or
decreasing capacity, depending on whether the pressure is above or below the Neutral Zone. The
rate at which the capacity increases or decreases depends upon the setting of the Minimum and
Maximum timers within the controller. This means that the further away the suction pressure moves
away from the Neutral Zone (either above or below), the quicker the controller will adjust the
compressor capacity.
On Digital twin compressor units, the compressor with the capacity control is always the first to start
and the last to stop.
Digital Scroll compressor motors are designed to run only in one direction. The correct rotation of a three
phase compressor motor depends on the connection of the three incoming phases to the unit. Correct
rotation can be determined by a drop in suction pressure and a rise in discharge pressure when the
compressor is energized. Running the compressor for a short period of time in reverse direction will have
no negative impact but prolonged running in reverse direction may cause premature failure.
To reverse
the rotation of a three phase digital scroll compressor, shut off the incoming power supply to the unit, swap
connection of any two of the three incoming phases at the unit isolator, reapply power to the unit and
following compressor restart, recheck operating pressures.
Digital compressor:
At initial start-up, the digital compressor will run at 50% capacity for three minutes followed by 1
minute at 100% capacity. Following this, the compressor will modulate the capacity according to the
system requirement in relation to the suction pressure set-point.
Vacuum operation:
Do not operate scroll compressors in a vacuum condition, as this will cause the scrolls to overheat very
quickly causing premature failure.
System charge:
Ensure an adequate liquid charge has been introduced to the high side of the system before starting
to ensure a minimum operating pressure on the suction side of 0.5 bar is maintained, otherwise
overheating of the scrolls and subsequent damage may occur.