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SECTION 5
ALARM SYSTEM
2.
Long Cycle: This light indicates a long
cycle time. When the pre-set maximum
cycle time
is reached, this alarm
will
be
activated.
Possible Cause: A faulty compressor, leak,
or any problem that causes the maximum
pre-set cycle time to be exceeded.
NOTE: The long cycle light will come on
by itself when the maximum cycle time
has been
exceeded.
However,
it will
come
on with the high pressure
light
when a high pressure situation exists in
the unit. Further testing must be done to
determine
the
exact
cause
of
the
problem.
Refer
to
the
Service
Instructions, Section
7 for the
proper
testing procedures for the compressor or
purge depending on which alarms come
on. See number 4 below: High Pressure.
No Cycle: This light indicates a failure of
the four-way valve to shift properly.
Possible Cause: Defective or sticking four-
way
valve, inadequate
pilot pressure,
faulty wiring from valve to MC board, or
defective MC board. A severe restriction
of flow or contaminated
beds may also
activate this alarm.
NOTE: The short and no cycle lights will
come on together whether it is a four-
way or bed failure. Further testing must
be done to determine the exact cause of
the
problem.
Refer
to
the
Service
Instructions, Section 7 for the
proper
testing procedures for the four-way and
sieve beds.
High Pressure: This light indicates a high
pressure situation in the system.
Possible Cause: Purge valve remained in
the activated position due to a defective
MC board or sticking valve.
NOTE: The high pressure and long cycle
lights will come on together when a high
pressure
situation
exists
in the unit.
Further
testing
must
be
done
to
determine
the
exact
cause
of
the
problem.
Refer
to
the
Service
instructions, Section
7 for the
proper
testing procedures for the purge valve.
When any of the four red indicator lights
come
on
the
compressor
will
automatically shut off but the cooling fan
will
continue
to operate.
Also,
the
audible alarm will sound and the "Service
Required" light on the control panel will
illuminate.
The MC board also has two green indictor
lights (8 Fig. 12) labeled
"purge"
and
"four-way." These are not alarm lights.
Purge:
This green
indicator
light will
come on only when
the purge valve is
activated (approximately 1.0 seconds).
Four-Way: This green indicator light will
come on only when the four-way valve is
activated. At the same
time the
right
sieve bed is being pressurized. When it is
off, the left bed is pressurizing.
Important:
Instead
of
the
alarm
designations
explained
in this section
(Short Cycle, Long Cycle, No Cycle, High
Pressure) some
DeVO/MC44's
may
have
the following alarm light designations:
Bed,
Purge/Compressor,
4-way,
High
Pressure.
These
were
used
on
the
DeVilbiss Models MC29 and DeVO/44. in
either case they refer to the same type of
malfunctions
and
should
be used
the
same way.
10/87
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