1. MCS-Magnum Chiller Logic
REVISED-VER.L-11/11/2018

2. MCS-Magnum Block Diagram
Memory
Flash Memory (8MB)
RAM Memory (2MB)
Firmware
Operation System
Control Logic
Communications
Scan Keypad
Write the LCD display
Control Variables
Control States
History/Trending
Communication
Alarm History
Configuration
Setpoints
#of Compressors
Refrigerant type
Etc.
Zilog MicroController
Microprocessor
Real Time Clock
Ethernet
RS485
MCS-I/0
Inputs/Outputs
Relay outputs
Sensor inputs
Analog outputs
HMI
Key pad/LCD

3. MCS-Magnum Firmware Versions
HVAC 17.XX - Chiller / Condensing Loop Water Units
CENT 17.XX- Centrifugal Chillers
REFR 17.XX - Refrigeration Storage Units
RTU 17.XX - Roof Top Package A/C Units
CPM 17.XX – Chiller Plant Controller

4. MCS-MAGNUM HVAC FIRMWARE (using HVAC 17.XX version)
Up to 20 compressors/refrigeration circuits
Up to 4 stages per compressor
All Compressor Types
Reciprocating
Screw
Centrifugal
Scroll
All Condenser Types
Air-cooled
Water-cooled
Evaporative-cooled

5. MCS-MAGNUM HVAC FIRMWARE
All Evaporator Types
Shell and tube
Flooded barrel
Plate heat exchanger
Dx air coil
Chilled Water Reset
Hard wired
Network
Automatic

6. MCS-MAGNUM HVAC FIRMWARE
Two Independent Electronic Expansion
Value (EXV) Controllers per Compressor
EXV Control for Compressor Subcooler
Pump Down / Disable switches
Low Suction PSI Unloading
High Discharge PSI Unloading
High Discharge Temperature Unloading
High Ampere Unloading & Holding
Low Evap Temp Unloading & Holding

7. MCS-MAGNUM HVAC FIRMWARE
Energy Efficient Compressor Staging
Chiller Water Pump Control (Primary / Standby)
Part Wind, Star Delta or Across the Line
(Fix Time or Dynamic)
Low & High Ambient Shutdown
English, Metric, or Mixed Sensor Readings
Compressor Auto Rotation
(Lowest Run Hours or First on/First Off)

8. MCS-MAGNUM HVAC FIRMWARE
User Logic-Custom Logic
SI -config

9. MCS-Magnum Control Logic
The Control logic runs every second:
Reads all sensor inputs
Checks chiller safeties
Checks compressor(s) safeties
Runs unit state control logic
Runs once for each compressor:
Runs compressor state control logic
Runs evaporator EXV state control logic
Run subcooler EXV state control logic
Runs Condenser logic
Save input & outputs reading for graphic/trending
Write Relay and Analog Outputs

10. MCS-MAGNUM HVAC FIRMWARE
Look Up Tables ( shown in MCS-CONNECT)
Voltage  Surge Curves  Thermistor Curves
Curves in User Logic

11. Simplified Unit State Control Logic
A State machine which operates based on the sensor inputs & configurations to control the unit
Switches states based on sensor inputs
The relay outputs and analog outputs are determined by the current state
Simplified Unit State Control Logic
UNIT IS LOADING
UNIT IS HOLDING
UNIT IS UNLOADING
‘RUN/STOP SW OFF’
State

12. State Control Logic The MCS-Magnum runs four state controls:
Unit Control Logic
Compressor Control Logic
Evaporator EXV Control Logic
Subcooler EXV Control Logic
These states along with their relevant information can be viewed in the System Status window of MCS-Connect and status option on MCS-Magnum Keypad/LCD display

13. Viewing The Current State In MCS-Connect
Unit Control Information
Time
Time in the current state
Current State
Step Delay
Value that is counted down. When this value reaches zero, the controller will determine if a change in the system capacity is required
Ref Type
Refrigerant type used
Wanted %
Wanted compressor percentage
Wanted/Actual
Number of capacity steps Wanted On versus Number of capacity steps Actually On
Current Rate of Change
Rate of change (up to 60 seconds) of the current controlling sensor
Current Controlling Sensor
The current value of the controlling sensor
Background color changes based on proximity to target temperature
Mode
Mode is either Cooling, heating, or ice making

14. Viewing The Current State In MCS-Connect
Compressor Control
Current State
Time
Time passed in the current state
PSI Diff
Current calculated oil pressure
FLA %
Current percentage of full load amps
Steps
The current number of steps that are turned on for this compressor
Lead?
The lead compressor will have a ‘Yes’ in this column

15. Viewing The Current State In MCS-Connect
EXV Control
Current State
Time
Time passed in the current state
Valve %
The current percentage of each EXV
Control On Suct. Supht
The current value of the superheat for this compressor
SuperHeat ROC
The rate of change of superheat based on the time defined in the superheat target setpoint
ADJ Delay
When this value reaches zero, the controller will adjust the EXV based on the current status

16. Viewing The Current State In MCS-Connect
Additional Circuit Information

17. Viewing The Current State In MCS-MAGNUM
CURRENT ‘STATE OF THE UNIT’ – Press PG 
HH:MM UNIT
UNIT STATUS
TIME IN THIS STATE
HEADING
CURRENT DATA FOR THE UNIT
TARG
SELECT PAGE UP/DOWN
STATUS OF ‘COMP1’ – Press PG 
HH:MM UNIT BEING CONTROLLED
COMPRESSOR STATUS
TIME IN THIS STATE
HEADING
CURRENT DATA FOR THE UNIT
SELECT PAGE UP/DOWN

18. Viewing The Current State In MCS-MAGNUM
CURRENT STATUS OF ‘EXV 1’ – Press PG 
HH:MM EXV 1
STATUS
TIME IN THIS STATE
HEADING
CURRENT DATA FOR THE UNIT
TARG
SELECT PAGE UP/DOWN
CURRENT STATUS OF ‘COMP2’
HH:MM COMPRESSOR 2 STATUS
STATE OF COMPRESSOR
TIME IN THIS STATE
HEADING
CURRENT DATA FOR THE UNIT
SELECT PAGE UP/DOWN

19. Unit States
UNIT IN POWER UP System Reset or Power Returned (delay of 60 seconds or set point value)
UNIT IS OFF System ready to run but no cooling capacity required
UNIT IS HOLDING No change in capacity.
UNIT UNLOADING Reducing chiller capacity - unloading.
UNIT IS LOADING Increasing chiller capacity - loading
UNIT UNLOADED Chiller is fully unloaded - all stage of cooling capacity are off.
UNIT IS LOADED Chiller is fully loaded - all available stages of cooling capacity are on.
RUN/STOP SW OFF RUN STOP sensor input is OFF - chiller turned off.
OFF- NO EVAP FLOW FLOW SW sensor input is OFF - chiller turned off.
SCHEDULED OFF Operating schedule is false.
AMBIENT OFF Low Ambient Temperature - chiller turned off.
UNIT IN LOCKOUT Chiller locked out, all points except alarm point are OFF
NO RUN- I/O LOST Lost communication Chiller locked out
Chiller is fully loaded - all available stages of cooling capacity are on.

20. Compressor Control States
LOST IO LOCKED This state is entered when the Capacity Control State is NO RUN- I/O LOST.
CMP LOCKED OUT The compressor is in a lockout state
SWITCHED OFF This state is entered when the compressor is off due to the pump down switch being on or the compressor flow switch being off.
UNLD and PMPDWN This state is entered when the pump down switch has been turned on or if this compressor is no longer Wanted On
CMP ANTICYCE This state is entered when the UNLD and PMPDWN state has been completed
CMP OFF/READY This state is entered when no capacity is required from this compressor, or the last state was CMP ANTICYCE, LOST I/O LOCKED, or SWITCHED OFF.
OIL PMP LUBING This state is used to ensure proper oil flow prior to compressor startup
CMP UNLOADED In this state the compressor is supplying its minimum cooling capacity.
CMP IS HOLDING In this state, the required refrigeration capacity of system is being met; no movement of the slide valve is required.
FAST UNLOADING For screw compressors only, this state is entered when the compressor is turned on.
LO SUCT UNLOAD The capacity is being unloaded due to low suction pressure.
LO SUCT HOLD Capacity is being held due to low suction pressure
HI DISC UNLOAD The capacity is being unloaded due to a high discharge pressure, high discharge temperature, or low discharge superheat.
HI DISC HOLD Capacity is being held due to high discharge temperature or pressure.
SAFETY TRIPPED This state is entered when a safety trip occurs but a lockout is not generated.
LO TMP UNLOAD This state is entered when the leaving liquid temperature is too low
LO TMP HOLD This state in entered after releasing from LO TMP UNLOAD
HI AMP HOLD This state occurs when a fully loaded compressor experiences an abnormally high amp draw.
HI DIS TMP HLD This state is entered when a fully loaded compressor that has more than one step encounters a high discharge temperature.
*Please see the MCS-Magnum manual for a complete list of compressor Control States

21. EXV & Subcooler States
LOCKED OUT The compressor is in a Lockout state.
EXV IS CLOSED The associated compressor is OFF and the valve is closed
PRE-PMPDWN The valve has been in a closed state and the system is now requiring the valve action.
EXV IN STARTUP At startup the valve will remain in this state for the time in Setpoint #20. At that time the state will be changed to holding, at this point the valve control logic will position the valve.
EXV AT 100% This state will be entered when the valve opening reaches 100%.
EXV IS HOLDING Refer to EXV Logic Chart, superheat is in control zone and ROC is acceptable.
EXV IS OPENING Refer to EXV Logic Chart, superheat is in control zone but rising too fast, ROC less than 1.0.
EXV IS CLOSING Refer to EXV Logic Chart, superheat is in the control zone and the rate of change is acceptable, ROC greater than –0.5.
LOW SPRHT Refer to EXV Logic Chart, force a course valve adjustment.
OPENING 4x Refer to EXV Logic Chart, superheat is above control zone.
OPENING 2x Refer to EXV Logic Chart, superheat is in control zone but rising too fast, the ROC is greater than 1.0.
LO PSI OPN Refer to EXV Logic Chart, state indicates that a low suction pressure condition exists. The suction pressure is less than Setpoint #77 “LOW SUCTION” plus twice the value of Setpoint #79 “LOW SUCT RELOAD” and the superheat is greater than Setpoint #9 “SUPERHT TRGT” plus twice the value of Setpoint #10 “SPRHT ZONE+-“.
CLOSING 2x Refer to EXV Logic Chart, superheat is in the control zone and the rate of change is acceptable, the ROC is less than -0.5 and greater than -1.0.
CLOSING 4x Refer to EXV Logic Chart, superheat is in control zone but falling too fast, ROC less than -1.0.
HI LVL CLS This state indicates that a high refrigerant level. This state is entered if Setpoint #109 “HiRefLevel” is active and the superheat is greater than the value of this Setpoint.
EXV MOP CLS Refer to EXV Logic Chart. Maximum operating pressure option is active and it is forcing the EXV to close. In this state the EXV valve’s opening will be reduced.
EXV MOP HLD Refer to EXV Logic Chart. Maximum operating pressure option is active and it is forcing the EXV to hold.

22. The ‘Steps’ result from the relay turning ‘On or Off’
Fixed Step Capacity
Unit capacity can be controlled by turning on or off:
Compressor(s)
Unloader(s)
Hot Gas Bypass
The ‘Steps’ result from the relay turning ‘On or Off’
NOTE: The ± Control Zone should be large enough to eliminate cycling!

23. Variable Step Capacity
Unit capacity can be controlled by modulating:
Screw compressor slide
Compressor(s) with a VFD
Centrifugal with vanes
Digital Scroll
The line results from modulating control

24. Zone Control Target (Setpoint #1)
The desired value to maintain the controlling sensor at
Control Zone+ & Control Zone- (Setpoint #2 & #3)
Allowable range around the target
Above the zone
Unloaded On:
Setpoint 151 setback
Can be set to a number, or an offset of the target
Upper Control Zone:
Setpoint 1 plus 2
In the zone
Target:
Setpoint 1
In the zone
Lower Control Zone:
Setpoint 1 minus 3
Unloaded Off:
Setpoint 151
Can be set to a number, or an offset of the target
Below the zone
Below the unloaded off limit

25. Chiller Control Decision Making
Set points establish target / control zone & unloaded off limit
How far from the target setpoint is controlling sensor input
How fast is the controlling sensor input moving to or away from the control target
The decision is then made to increase, decrease or maintain the cooling capacity
Capacity Control based on:
Entering temperature or one sensor input
Leaving liquid temperature or Suction PSI
Controlling sensor’s rate of change (ROC) is calculated

26. Rate of Change
4 hours
120
miles
120 miles
4 hours
of driving

27. Rate of Change In Chillers
Rate of change is used as a hold mechanism, which holds the capacity if the temperature is moving quick enough
Set points
#27 Max ROC- - Max. (negative) ROC above control zone.
#28 Max ROC+ - Max. (positive) ROC below control zone
#29 ROC Interval - ROC time period (in seconds, max 60s)
Setpoints #27 & #28 define the speed limits for the change in temperature

28. Applied Rate of Change Logic
Control above the zone
Unit Control Starts in LOADING
Current ROC > MAX ROC-
Unit Control continues LOADING
Current ROC ≤ MAX ROC- Unit Control HOLDS

29. Applied Rate of Change Logic
Control below the zone
Unit Control Starts UNLOADING
Current ROC < MAX ROC+
Unit Control continues UNLOADING
Current ROC ≤ 1°F/s Unit Control HOLDS

30. Applied Rate of Change Logic
Unloaded off Logic
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.
Unit continues UNLOADING
Unit UNLOADING
Unit continues UNLOADING
UNLOADED OFF
Unit OFF when below UNLOAD OFF VALVE

31. MCS Safeties High Discharge Unloading, Holding, Trip Logic # VALUE
NAME
DESCRIPTION 81
360
HI DISC PSI
If active, the Magnum checks for high discharge pressure for each running compressor. If the discharge pressure sensor reads greater than this Setpoint for the specified period of time, a safety trip will occur.
Refers to ‘Discharge Pressure’ column in the Circuit SI screen. 82 20
HI DISC UNLD
The purpose of this Setpoint is to take corrective action to prevent a high discharge pressure safety trip. For fixed step compressors: If a compressor has more than one step, is fully loaded, and if the discharge pressure is more than the value of Setpoint #81 “HI DISC PSI” minus the value of this Setpoint, then one step of capacity will be turned off. For variable step compressors: If a compressor has a discharge pressure more than the value of Setpoint #81 “HI DISC PSI” minus the value of this Setpoint, then the compressor will be forced to unload. The circuit state will be changed to HI DISC HOLD, and will remain in this state for a minimum of the time in Setpoint #101 “SAFETY HOLD DELAY”. At that time, if the discharge pressure has decreased below than the value of Setpoint #81 “HI DISC PSI” minus the value of Setpoint #83 “HI DISC RELD” the compressor will return to normal control. 83 50
HI DISC RELD
Refer to Setpoint #82 description.

32. List of Compressor Safeties
Low Suction Pressure
Unsafe Suction Pressure
High Discharge Pressure
High Discharge Temp
Low Oil Differential Pressure
Unsafe Oil Differential Pressure
High Oil Temperature
High Motor Temperature
Low Suction Super Heat
High Oil Seal Temperature
Dirty Oil Filter
Motor Fault
Emergency Stop
No Flow Protection
Freeze Protection
Low Amps (3 Phase)
High Amps (3 Phase)
Low Refrigerator Temperature

33. MCS Alarm Notifications
Alarms are displayed most current first
Reason for the alarm, for example “LOW SUCTION #1” a low suction alarm for circuit #1 was generated
Each alarm is date/time stamped e.g. “MAY 30 13:17:33”
All compressor safety have 120 seconds of run data
A lock out situation will not be created unless the same alarm occurs twice within a specified time, except Phase Loss, EMG/STOP, unsafe suction

34. Diagnostic Save Button
A Diagnostic save will do the following:
Saves the Config file
History Printout
Last 5 Lockouts Alarm Printout
Status Printout
Saves a Zip file to your computer and can
Auto zip file to:

35. Training Class Exercise 1
Load the compressor to 100% capacity
Place the RUN/STOP in the RUN state
set the CHIL WTR sensor input higher than the target to simulate a demand
The Step Delay will be decremented by the distance from the current value to the target
When the Step Delay reaches zero, the system calculates the ± % change in capacity.

36. Training Class Exercise 2
Silmulate High Discharge Temperature Unloading
For variable step compressors only. The capacity is being unloaded due to a high discharge temperature.
The compressor will stay in this state until the pressure or temperature has dropped below the corresponding Setpoint. The system will then move to the HI DISC HOLD state.
Place the RUN /STOP in the RUN state
Discharge Temperature of compressor is 235
Setpoint #87 HI DISC TEMP value is 230
Setpoint #88 DISC TEMP UNLD value is 7.5 seconds
Setpoint #101 SAFETY HOLD DELAY is 120 seconds
The Magnum will begin unloading the compressor(s) with high discharge temperature until the temperature drops below the calculated value. During this time the circuit state is HI DISC UNLOAD. Once this temperature has been reached, the circuit state will be HI DISC HOLD. The compressor will remain in that state until the capacity control indicates that less capacity is needed or if the discharge temperature has returned to normal after the time in Setpoint #101 “SAFETY HOLD DELAY” has passed.

37. Questions?