MCSMagnum Chiller Logic www mcscontrols com REVISEDVER M11282020

MCS-Magnum Chiller Logic www. mcscontrols. com REVISED-VER. M-11/28/2020

MCS-Magnum Block Diagram Memory Flash Memory (8 MB) Firmware • Operation System • Control Logic • Communications • Scan Keypad • Write the LCD display Configuration • Setpoints • #of Compressors • Refrigerant type • Etc. RAM Memory (2 MB) Control Variables • Control States • History/Trending • Communication • Alarm History Zilog Micro. Controller • Microprocessor • Real Time Clock • Ethernet • RS 485 • 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 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 § SI -config User Logic-Custom Logic

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 in User Logic Thermistor Curves

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 UNLOADING ‘RUN/STOP SW OFF’ State UNIT IS HOLDING

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

Viewing The Current State In MCS-Connect Compressor Control Current State Time PSI Diff FLA % Lead? Steps The leadnumber compressor Current percentage Time passed in calculated The of current of have ‘Yes’ in this oilfull pressure load amps stepswill the current that areaturned column state on for this compressor

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

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 STATUS TIME IN THIS STATE HEADING CURRENT DATA FOR THE UNIT TARG SELECT PAGE UP/DOWN STATUS OF ‘COMP 1’ – 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 ‘COMP 2’ 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 UNIT IS LOADING Reducing chiller capacity - unloading. Increasing chiller capacity - loading UNIT UNLOADED UNIT IS LOADED Chiller is fully unloaded - all stage of cooling capacity are off. 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 SW sensor input is OFF - chiller turned off. SCHEDULED OFF Operating schedule is false. AMBIENT OFF UNIT IN LOCKOUT NO RUN- I/O LOST Low Ambient Temperature - chiller turned off. Chiller locked out, all points except alarm point are OFF 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 LO TMP UNLOAD LO TMP HOLD HI AMP HOLD HI DIS TMP HLD This state is entered when a safety trip occurs but a lockout is not generated. This state is entered when the leaving liquid temperature is too low This state in entered after releasing from LO TMP UNLOAD This state occurs when a fully loaded compressor experiences an abnormally high amp draw. 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 CLOSEDThe 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 OPENING 4 x OPENING 2 x Refer to EXV Logic Chart, force a course valve adjustment. Refer to EXV Logic Chart, superheat is above control zone. 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+-“. 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. Refer to EXV Logic Chart, superheat is in control zone but falling too fast, ROC less than -1. 0. This state indicates that a high refrigerant level. This state is entered if Setpoint #109 “Hi. Ref. Level” is active and the superheat is greater than the value of this Setpoint. CLOSING 2 x CLOSING 4 x HI LVL CLS 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.

Fixed Step Capacity Unit capacity can be controlled by turning on or off: § Compressor(s) The ‘Steps’ result from the relay turning ‘On § Unloader(s) or Off’ § Hot Gas Bypass NOTE: The ± Control Zone should be large enough to eliminate cycling! Fixed Step Capacity 100% 75% Capacity § 50% 25% 0% 0 1 2 3 Number of Steps On 4 5

Variable Step Capacity Unit capacity can be controlled by modulating: § Screw compressor slide § Compressor(s) with a VFD § Centrifugal with vanes The line results from modulating control § Digital Scroll Variable Capacity 100% 75% Capacity § 50% 25% 0%

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 Unloaded On: Setpoint 151 setback Can be set to a number, Upper Control Zone: or an offset of the target Setpoint 1 plus 2 Above the zone In the zone Target: Lower. Setpoint Control 1 Zone: In the zone Setpoint 1 minus Unloaded Off: 3 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 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 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#28 Max ROC+ #29 ROC Interval - Max. (negative) ROC above control zone. - Max. (positive) ROC below control zone - ROC time period (in seconds, max 60 s) Setpoints #27 & #28 define the speed limits for the change in temperature Negative Rate Of Change Positive Rate Of Change 300 200 100 0 0 0 5 10

Applied Rate of Change Logic § Control above the zone Unit Control Starts in LOADING Current ROC > MAX ROCUnit Control continues LOADING Current ROC ≤ MAX ROCUnit 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 UNLOADING Unit continues UNLOADING UNLOADED OFF Unit OFF when below UNLOAD OFF VALVE

MCS Safeties § High Discharge Unloading, Holding, Trip Logic # 81 VALUE 360 NAME HI DISC PSI 82 20 HI DISC UNLD 83 50 HI DISC RELD DESCRIPTION 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. 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. Refer to Setpoint #82 description.

List of Compressor Safeties § Low Suction Pressure § High Oil Seal Temperature § Unsafe Suction Pressure High Discharge Temp Low Oil Differential Pressure Unsafe Oil Differential Pressure High Oil Temperature High Motor Temperature Low Suction Super Heat § 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 (Popup) (available in MCS-CONNECT Version 18. 22. 20) The Diagnostic Save Popup can be activated when you are connected to a controller either by ‘Serial’, ‘Ethernet’ or connect ‘Remotely’. Screen shows all controllers on network Click on the ‘DIAGNOSTIC SAVE’ button. The Diagnostic Save Popup will appear. If you have multiple controllers connected to the network, you can choose a ‘Diagnostic Save’ for each controller, choose the option of what information you want saved by clicking the boxes.

Diagnostic Save (Popup) A second popup will appear showing the file has been saved to your hard drive. You have the option to email the zip saved file to: support@mcscontrols. com or to a custom email address (Internet connection required) dew@mcscontrols. com Below shows file that was emailed as per the setup in the ‘Diagnostic Save’.

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 230 Setpoint #87 HI DISC TEMP value is 235 Setpoint #88 DISC TEMP UNLD value is 10 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.

Questions? For additional information please visit our website www. mcscontrols. com Or call MCS at 239 -694 -0089 5580 Enterprise Pkwy. Fort Myers, FL 33905 Office: 239 -694 -0089 Fax: 239 -694 -0031 www. mcscontrols. com