16
17
PUMP-DOWN STAGE :
The PUMP-DOWN procedure can
be enabled through H1 parameter.
3.8 PUMP-DOWN
B.
T h e c o m p r e s s o r k e e p s
operating until the LOW pressure
cutout
input
intervenes.
C.
When the system cuts off on the
input from the low pressure cutout,
the compressor turns OFF and the
PUMP-DOWN procedure is over.
A.
De-energisation of the Liquid
Solenoid Valve.
If the compressor remains on for
more than 50 seconds without
cutting off on the low pressure
switch, Megachill will force a
compressor shut down and
indicate a FAULTY PUMP-DOWN
procedure provided the CUT IN
temp has not been achieved. In
this case check the LIQUID
SOLENOID VALVE and LOW
PRESSURE CONTROL. If within
50 seconds, the CUT IN temp has
been achieved, the system will
activate the solenoid and continue
operating normally without pump
down.
PUMP-DOWN CYCLE
3.9 Water Level
A pump-down cycle is used to
pump all refrigerant into a receiver
or condensor during the OFF cycle.
The purpose is to prevent
refrigerant from migrating to the
crankcase, where it can condense
and saturate the oil. Without a
pump-down cycle, the crankcase
can fill liquid refrigerant during a
long off-cycle. At start up, the liquid
refrigerant can flood the cylinders
and damage the compressor much
l i k e a f l o o d b a c k . ( L a r g e
compressors have springs on
intake) After the system has cooled
the evaporator sufficiently, a
solenoid valve closes in the liquid
line and the compressor pumps
refrigerant into the condenser or
receiver, where it remains until the
next on-cycle.
System controls the level of water
in the evaporator tank via three
water level sensors, High, Med &
Low. As soon as the level of water
goes below the Med level, the
controller will activate a Water
Solenoid Valve. In case the level
goes below the Low level sensor,
the system trips and displays a Low
Liquid Level Fault.
If the machine controlled by mega chill is not using
the water level sensing feature, it is necessary to
short all water inputs concerning the water level.
This will disable the liquid level errors.
WARNING
4.1 Programming Levels
There are two programming levels allowing authorized personnel to
enter and change parameters
AFT Probe calibration
3) Press SEL again to display the
required user parameter and
modify it’s value with the UP
and DOWN key.
4.2 USER PARAMETERS
Temperature set point
System Auto start
Keypad Lock
Can be directly accessed by the
user for the selection of
Control Probe calibration
2) Using the UP and DOWN arrow
keys allows scrolling all user
parameters.
LEVEL 1 - USER
1) If you press and hold SEL for 4
seconds, the display shows the
code of the first parameter.
Setting of all parameters.
LEVEL 2-
MANUFACTURER
Can only be accessed by the
chiller manufacturer via a
PROKEY for.
4. PROGRAMMING
