Engineered Control Systems

For larger and more complex operations, M&M Systems implements an Engineered Control System. The system utilizes one or more microprocessor-based control panels to perform all system functions. The control panels may be networked to form a fully customized system tailored specifically to meet a client’s operational requirements. A system could consist of a Master control panel (with keypad and display), Remote panels (no display) and several Compressor control panels.

Control of refrigeration system components such as condensers, evaporators, refrigeration pumps, etc. can be housed in a single control panel to form a centralized system or distributed among several panels based on customer needs thus reducing wiring cost. Another feature is expandability, every system we install is fully expandable which allows for cost-effective expansion as your business grows. Expansion is easily accomplished by incorporating additional I/O boards into existing control panels or by adding control panels.

Condenser Control


  • Programmable pressure set point, dead band, and bandwidth
  • User configurable lead list for the fans and pumps may be modified at any time
  • Hot lead list change allows for smooth transitions when changes are required
  • Stages may be temporarily removed from the lead list at any time
  • Programmable normal and fast staging delays for quick response
  • Support for two-speed fans. Lead list for two-speed fans is operator selectable to allow staging of all low speed fans first followed by the high speed fans


  • Support for variable speed fans or pumps using Auto tuning PID control. Each fan is started as needed at user defined minimum speed. The speed of all of the fans is then varied required
  • Wet bulb control option
  • Non-condensable calculation and alarm monitoring
  • Summer/Winter lead lists which can be automatically selected based on ambient air temperature or at a scheduled time
  • Condenser pump shutdown based on user defined conditions
  • Shell-and-tube condenser control
  • Condenser scheduling with defrost set points
  • Condenser shutdown based on user defined conditions

Pump Package Control


  • Up to five (6) discrete liquid level float switches (LLCO, LLA, OP1, OP2, HLA, and HLS) -and/or-
  • Analog continuous liquid level sensor with programmable set points for HLS, HLA, OP1, OP2, LLA, and LLCO levels and their individually programmable dead bands
  • Up to two (2) liquid feed solenoid valves with one or two independent level control set points
  • Operation of liquid feed solenoid valves based on liquid level
  • Up to five (5) pumps with auxiliary contacts
  • Automatic starting of back-up pumps based on lead pump failure
  • When no compressors are available, the pumps may be set to stop and the liquid feed solenoid may be closed
  • Pumps can be set to restart automatically after a power fail reset with a user programmable maximum down time
  • Pumps can be set to stop when no liquid is required by the zones
  • Pumps are always stopped during a low level cut-out condition and only allowed to re-start after the operating level is reached


  • Modulating liquid solenoid using auto tuning PID algorithm
  • Optional liquid temperature sensor
  • Optional pump suction and discharge pressure sensors.
  • Anti-cavitation logic based on pump discharge pressure
  • Compressors can be stopped via communications when a HLS condition occurs

Evaporator Control


  • Set point scheduling (zone independent):
    - Four programmable set point groups
    1) cooling set point
    2) dead band
    3) high alarm & low alarm
    4) heating set point option
    - Three daily schedules each with eight time slots
    - Manual override provided for schedule number and set point group
  • Air unit fans may be individually set to cycle with temperature or remain running. A programmable fan cycle off-time delay and/or on-time delay is also provided
  • When the fans for a zone are cycled off due to temperature, the fans may be cycled on for a short period of time to sample the room air before resuming normal operation
  • Support for various zone defrost types (hot gas, water, air, etc.)
  • Zone high temperature alarms are inhibited during defrost cycle and for a user programmable delay after defrost completion
  • Manual override control of zone state (cooling, stop, manual, defrost, pump-out)
  • Adaptable to match each zones specific valve station configuration
  • Defrost scheduling:
    - Defrost based on liquid feed run-time or fixed time schedules
    - Programmable defrost times using three daily schedules with eight time slots
  • Power fail staging to slowly bring zones on-line after power failures based on user defined staging time and zone priorities.
  • User-programmable set points to enable and disable defrosting based on head pressure
  • Ability to inhibit defrosting of zones when no compressors are available
  • Ability to terminate defrost manually to force zone back to cooling state
  • Ability to separate zones into different defrost queues to select number of zones which can defrost at a time


  • Zone shutdown due to NH3 detection or other user defined conditions
  • Demand defrost based on discrete input, temperature differential across the coil or fan motor current
  • Priority defrost of pre-defined zones or based on user issued command
  • Heating option allows zone to maintain a heating set point. Optional ability to disable heating based on user-defined conditions.
  • Variable speed fan control using PID control loop based on user defined weighted average between room air and return air temperature sensors
  • Two speed fans, variable speed fans, or variable suction regulator control

Blast Freezer Control


  • User programmable blast run-time length
  • Manual start or automatic start based on user programmed start time and day of week
  • Blast freezer can be set to stop, defrost then stop, or hold at end of blast run-time
  • Priority defrost allows a blast zone to be the next zone allowed to defrost
  • Blast operating state can be overridden by the user
  • Blast staging to provide a programmable delay between multiple blast cell starts


  • Demand defrost based on temperature differential across coils or fan motor current
  • Ability to display blast run-time either counting up or down
  • Priority defrost of zones based on user issued command
  • Blast termination based on product probes
  • VFD fan control based on user defined fan speed profile/schedule

KW Monitoring


  • KW monitoring using either KW pulse meters, KW meters or current transformers
  • Calculation of total energy used and current demand. The following KW calculations are performed and displayed: KW/hour, KW/day, KW/week, and KW/year
  • Tracks highest demand for the day with time of occurrence
  • High Demand Alarm
  • KW log records daily totals


  • Multiple circuits and separate control to match facility
  • Communications to power meters for additional power parameters

KW Load Shedding


  • Uses KW monitoring data
  • Shutdown evaporators to maintain demand KW below user defined limits
  • User programmable normal and fast response delays
  • Set point scheduling:
    - Four programmable set point groups (demand KW set point, normal bandwidth, control dead band, normal stage delay, and fast stage delay)
    - Three daily schedules each with eight time slots
    - Manual override provided for schedule number and set point group
  • Ability to enable/disable each zone for load shed and prioritize enabled zones
  • Looks at zone temperature compared to set point and shuts down closest zones first
  • If a zone warms up to user defined limits it will be restarted


  • Ability to add non-refrigeration equipment to the shed list and prioritize

Data Logging


  • Operation log which displays a list of the system’s operating conditions for the last hour, at 30 second intervals
  • Trend log which displays the same system operating conditions as the operation log, but allows the user to define the recording interval value (default is 15 minutes) and has a limit
  • Approximately 200 recorded data entries
  • Alarm log which is a record of the last 100 system alarms
  • Failure log which is a record of the last 100 system failures
  • User log which is a record of the last 50 users logged onto the system including location of log on
  • Any system alarms or failures are also inserted into the operation and trend log at the time they occur regardless of the log’s recording interval


  • User defined custom logs to store data on anything from number of times a valve opened to the KW electric cost over a period of time
  • System logging maintains all system status information and can be down loaded to the PC for viewing

Compressor Sequencer Control


  • Stages multiple compressors on one or more common suction lines
  • One set of common control parameters on the master sequencer is used for all compressors to eliminate sensor differences and piping loss
  • Adjustable staging parameters for both load and unload conditions
  • Starting of next compressor inhibited until trim compressor is fully loaded or limited
  • Re-configurable lead lists allows easy addition or removal of swing compressors
  • Multiple lead lists to allow different compressor configurations to be stored and scheduled (Standard is two with more available on request)
  • When lead lists are changed, compressors start and stop in a controlled manner to smooth out transitions
  • Starting of skipped compressors using a standby monitor timer to maintain lead list order, as those compressors become available
  • Hot standby feature reduces starting and stopping of trim compressor
  • Support for screw, rotary, and reciprocating compressors
  • Set point and lead list scheduling:
    - Four (4) programmable set point groups (control set point, dead band, low alarm, and low failure)
    - Seven (7) daily schedules each with eight time slots
    - Each time slot contains a desired lead list and a desired set point group
    - Manual override provided for schedule number, set point group and lead list


  • Optional use of a common suction pressure sensor or one of the screw compressor sensors
  • Support for control parameters being changeable by the end user between suction pressure and process temperature
  • Separate dead bands for compressor starts/stops and capacity controls
  • Automatic interlocks between booster and high stage systems
  • Ability to force a compressor on in anticipation of a load
  • Support for disable ling sequencer based on conditions ( i.e. All zones are satisfied) stopping all compressors
  • Optional “smart” sequencing to allow efficient reconfiguration of the lead list under stable system conditions based on current part load capacity

Open Communication Options

Allen-Bradley DF1

  • Standard on all V2.00 and Higher Screw compressors. Also available on masters as required
  • Requires addition of communications board
  • Allows our controllers to respond like an Allen-Bradley PLC

Modbus RTU

  • Standard on all V2.06 and higher Screw compressors. Also available on masters as required
  • Uses PC Comm port on screws
  • May require comm board on masters (if PC is also required)
  • Originally developed by Modicon and now Widely accepted as a standard

External Communications Protocol (ECP)

  • Our own proprietary protocol for screw compressors
  • Requires Comm driver to be developed by customer
  • Compact, high speed communications

Frick Talk and Quantum Talk

  • Available on masters to allow control of Frick compressors via communications
  • Integrated into the PC interface to allow full access of compressors


  • Standard communications protocol for Building Automation and Control systems
  • High speed communications link allowing up to 76800 Baud.