Manitowoc J-1300, Руководство по обслуживанию

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Section 6 Electrical System
6-41
Troubleshooting PTCR’s
WHY A GOOD PTCR MAY FAIL
TO START THE COMPRESSOR
The PTCR must be cooled before attempting to start
the compressor, otherwise the high starting torque
may not last long enough.
For example, if the PTCR is properly cooled, say
60
°
F (15.6
°
C) when the compressor starts, it will take
.25 to 1.0 seconds before its temperature reaches
260
°
F (126.6
°
C), and current flow is stopped.
If the PTCR is still warm, say 160
°
F (71.1
°
C) when
the compressor starts, it will take only .125 to .50
seconds before its temperature reaches 260
°
F
(126.6
°
C), and current flow is stopped. This
decreased time may be insufficient to start the
compressor.
A good PTCR may be too hot to operate properly at
start-up because:
•
The ice machine’s 3-minute delay has been
overridden. Opening and closing the service
disconnect or cycling the toggle switch from OFF
to ICE will override the delay period.
•
The control box temperature is too high. Though
rare, very high air temperatures (intense sunlight,
etc.) can greatly increase the temperature of the
control box and its contents. This may require a
longer off time to allow the PTCR to cool.
•
The compressor has short-cycled, or the
compressor overload has opened. Move the toggle
switch to OFF and allow the compressor and
PTCR to cool.
There are other problems that may cause compressor
start-up failure with a good PTCR in a new, properly
wired ice machine.
•
The voltage at the compressor during start-up is
too low.
Manitowoc ice machines are rated at
±
10% of
nameplate voltage at compressor start-up. (Ex: An
ice machine rated at 208-230 should have a
compressor start-up voltage between 187 and 253
volts.)
•
The compressor discharge and suction pressures
are not matched closely enough or equalized.
These two pressures must be somewhat equalized
before attempting to start the compressor. The hot
gas valve (and HPR valve on remotes) energizes
for 45 seconds before the compressor starts, and
remains on 5 seconds after the compressor starts.
Make sure this is occurring before assuming that
the PTCR is bad.