MCS-Magnum Chiller Logic www.mcscontrols.com REVISED-VER.L-11/11/2018

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

Viewing The Current State In MCS-Connect Additional Circuit Information

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

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

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.

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

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.

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!

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

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

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

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

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

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

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

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

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.

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

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

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 Email zip file to: support@mcscontrols.com

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.

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.

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