The MHRC MAGNUM algorithm incorporates a number of safety checks to ensure MHRC unit operates in
a safe matter. When a unit safety trip occurs the MHRC’s control state goes to “ NO RUN-LOCK OUT”. The
unit will remain in this state until a lockout reset is perform via the LCD/Keypad or MCS-CONNECT.
21.4.2 Unit Safeties
For a safety to be interrogated, both the associated sensor input and the lockout setpoint must be active. If a
safety trips, the alarm name will consist of the setpoint name.
LOW SUPPLY TEMPERATURE
If the supply temperature falls below the value in calculated value of setpoint #1 “SUPPLY TARG” minus the
value in set point #54, “LO SUPPLY-T1” and it remains there for the time specifi ed in the safety time of that
setpoint, a “LO SUPPLY- T1” alarm generated. No change to system status will be made.
HIGH SUPPLY TEMPERATURE
If the supply temperature is greater than the value in calculated value of setpoint #1 “SUPPLY TARG” plus
the value in set point #55, “HI SUPPLY-T1” and it remains there for the time specifi ed in the safety time of that
setpoint, a “HI SUPPLY- T1” alarm is generated. No change to system status will be made.
UNSAFE SUPPLY TEMPERATURE
If the supply temperature is greater than the value in set point #59, “UnsafeSupply” and it remains there for
the time specifi ed in the safety time of that setpoint, the MHRC will be locked out and a “UnsafeSupply” alarm
is generated.
VFD FAULT
If the VFD FAULT input goes ON and it remains there for the time specifi ed in the safety time of setpoint
#57 “VFD FAULT”, the MHRC will be locked out and a “VFD FAULT” alarm generated. This fault requires a
manual reset via the LCD/Keypad or MCS-CONNECT.
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21.4 MHRC Unit Safeties
21.4.1 Introduction
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