Manitowoc Q130 series, Technician'S Handbook

Page: 111 / 236

Part Number 8001119 10/19 111
ANALYZING WHY SAFETY LIMITS MAY STOP THE
ICE MACHINE
According to the refrigeration industry, a high
percentage of compressor failure is a result of external
causes. These can include flooding or starving
expansion valves, dirty condensers, water loss to the
ice machine, etc. The safety limits protect the ice
machine (primarily the compressor) from external
failures by stopping ice machine operation before
major component damage occurs.
The safety limit system is similar to a high-pressure
cutout control. It stops the ice machine, but does not
tell what is wrong. The service technician must
analyze the system to determine what caused the
high-pressure cutout, or a particular safety limit, to
stop the ice machine.
The safety limits are designed to stop the ice machine
prior to major component failures, most often a minor
problem or something external to the ice machine.
This may be difficult to diagnose, as many external
problems occur intermittently.
Example: An ice machine stops intermittently on
safety limit #1 (long freeze times). The problem could
be a low ambient temperature at night, a water
pressure drop; the water is turned off one night a
week, etc.
When a high-pressure cutout or a safety limit stops the
ice machine, they are doing what they are supposed to
do. That is, stopping the ice machine before a major
component failure occurs.
Refrigeration and electrical component failures may
also trip a safety limit. Eliminate all electrical
components and external causes first. If it appears
that the refrigeration system is causing the problem,
use Manitowoc’s Refrigeration System Operational
Analysis Table, along with detailed charts, checklists,
and other references to determine the cause.