Technical Reference Manual-XPM3m Revision Date: August 2014
INDEPENDENT ALARM SCANNER OVER-TEMP & ALARM/SHUTDOWN
The Independent Alarm Scanner is:
Standard, (installed on all ovens) An option, (NOT installed on all ovens)
DESCRIPTION:
The Independent Alarm Scanner & Alarm/Shutdown (IAS) system provides a redundant temperature backup
system in the event that a heating cell exceeds the critical temperature safety limit. The hardware consists of one (1)
additional thermocouple per heat cell, and the Independent Alarm Scanner (IAS) instrument, which can monitor as
many as 32 thermocouples.
A second type K thermocouple is clamped on the face of every addition to the standard T/C
The Independent Alarm Scanner (IAS) receives each of these thermocouple signals as separate inputs and scans
them for an over-temperature indication.
The control circuit inter-action is:
In the event that an alarm condition (generated from the Redundant T/Cs) occurs, the IAS' alarm contact interrupts
the 24 VAC to relay K4. This in interrupts the 120 VAC to the coil of heater contactor K2, and supplies an alarm
signal to the controller. The IAS unit scans all redundant thermocouples wired to it for an “Over-temperature”
condition.
Notes:
All unused T/C terminals MUST be jumpered.
In case of a nuisance trip, the defective T/C can be found
by placing a jumper on the T/Cs one-at-a-time until the
“alarm” is eliminated.
The setpoint should be set slightly higher than the
temperature expected during “normal oven operation”.
The IAS will go into an alarm state in case of an IAS failure
or loss of power. A jumper on the output contacts will allow
the oven to be operated without the IAS until a replacement
can be installed.
Alarm setpoint adjustment
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