21
15. MHRC MODES
15.1. UNIT IN POWER UP
This state is entered when the Magnum is powered up or the system has been reset. The system will remain
in this state for the time specifi ed in set point #23 “POWER DELAY” or for 60 seconds if not active. In this
state all Relay Outputs are turned off. This time delay is to insure the microprocessor has stable power be-
fore starting the algorithm.
15.2. NO RUN- I/O LOSS
This state will be entered whenever the Magnum loses communications with any of the I/O boards that are
connected through the MCS I/O network. When this state is entered the Magnum will generate an MCS I/O
offl ine alarm, which identifi es which I/O is offl ine and a lost I/O shutdown alarm which locks out the unit. Once
locked out, if there are ten consecutive successful I/O reads the Magnum will reset and attempt to run. When
this occurs a “LOST I/O RESTART” will be generated. Or, the lockout-reset key can be pressed to reset the
Magnum, after the lost I/O has been corrected. This will generate a “LOCKOUT RESET.” In this state all RO’s
except ALARM and OIL HEATER are turned OFF.
15.3. UNIT IN LOCKOUT
15.4. UNIT IS OFF
This state is entered when the system has fi nished a STARTUP, DISABLE, LOCKOUT, or NO RUN- I/O LOST
state. The chiller is now ready to move into an active state to meet the capacity required.
15.5. UNIT IS HOLDING
This state is entered when one of three conditions exists:
1) The control sensor reading is being maintained with in the control zone.
2) Control sensor reading is above the control zone but the Rate of Change is less than the value in the
(MAX ROC-, #27) setpoint. This indicates that the temperature is decreasing toward the target at an accept-
able speed. Therefore, no additional cooling is needed at this time.
3) The temperature is below the control zone but the Rate of Change is greater than the (MAX ROC+, #28)
setpoint. This indicates that the temperature is increasing toward the target. Therefore, no reduction in cooling
is needed at this time.
This state indicates that there is no need to adjust the capacity of the chiller package. This state will end when
more or less capacity is required.
15.6. UNIT UNLOADING
This state is entered when less capacity is required. Every second an adjustment is made to the step delay.
When the delay reaches zero, the counter “steps wanted” on is decreased by 1.
This state is entered whenever a critical situation is encountered that could cause harm to the chiller pack-
age. Items such as freeze protect and emergency stop will force the system into this state. Lockouts can be
reset without authorization from the keypad or MCS-Connect program; however if the lockout condition has
not been corrected, the system will again be forced into the LOCKOUT state. In this state, all RO’s are
turned OFF and placed in the “LOCKOUT” state. Note: If the Lockout Reset is pressed more than the
programmed allowable number of times in one day the unit cannot be reset during the current day except
through MCS-Connect and requires Factory authorization. This number is selected from a drop down menu
under the Setup Information button, with a range of 2 to12.
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