Transcript Document

MCS-Magnum Chiller Logic
www.mcscontrols.com
Rev A
MCS-Magnum Block Diagram
Memory
Flash Memory (8MB)
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Firmware
Operation System
Control Logic
Communications
Scan Keypad
Write the LCD display
Configuration
Setpoints
#of Compressors
Refrigerant type
Etc.
Zilog MicroController
RAM Memory (2MB)
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Control Variables
Control States
History/Trending
Communication
Alarm History
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Microprocessor
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Real Time Clock
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Ethernet
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RS485
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MCS-I/0
Inputs/Outputs
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Relay outputs
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Sensor inputs
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Analog outputs
HMI
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Key pad/LCD
MCS-Magnum Firmware Versions
HVAC 16.XX - Chiller & Condensing Units
CENT 16.XX - Centrifugal Chillers
REFR 16.XX - Refrigeration Storage Units
RTU 16.XX - Roof Top Package A/C Units
MCS Control Options
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 Control Options
All Evaporator Types
Shell and tube
Flooded barrel
Plate heat exchanger
Dx air coil
Chilled Water Reset
Hard wired
Network
Automatic
MCS Control Options
Two Independent Electronic Expansion
Value (EXV) Controllers per Compressor
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 Control Options
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 Control Logic
The Control logic runs every second:
Reads all sensor inputs
Checks chiller safeties
Checks compressor(s) safeties
Runs unit state controller
Runs once for each compressor:
Runs compressor state controller
Runs EXV state controller
Runs Condenser logic
Stores graphing and trending data
State Controller
A State controller is a system that functions
based on its current state
Switches states based on sensor inputs
The relay outputs and analog outputs are
determined by the current state
Simplified Unit State Controller
LOADING
State
UNLOADING
State
RUN/STOP
State
HOLDING
State
State Controller
The MCS-Magnum runs three state controls:
Unit Control
Compressor Control
EXV Control
These states along with their relevant
information can be viewed in the System
Status window of MCS-Connect
State Controller in Connect
Unit Control Information
Current State
Mode
Step Delay
Ref Type
Wanted
%
Current
Rate of
Change Sensor
Wanted/Actual
Current
Controlling
Time
Mode
isthe
either type used
Value
thatWanted
is counted
Refrigerant
Ratecompressor
ofThe
change
(up value
to
60 of
Number
of
current
Time
passed
in capacity
Cooling, heating, or
down. When
this
value
seconds)
of the current
Wanted
Onpercentage
versus
controlling
sensor
the steps
current
zero, the
controlling sensor ice making
Numberreaches
of capacity
state
controller
steps Actually
On will determine
Background color changes
if a change in the system
based on proximity to
capacity is required target temperature
State Controller in Connect
Compressor Control
Current State
Time
PSI Diff
FLA %
Lead?
Steps
The
leadnumber
compressor
Current
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
State Controller in Connect
EXV Control
Current State
Time
Valve
Control
% OnSuperHeat
Suct. Supht
ADJ
ROCDelay
The current
The rate
value
When
of change
of
this
thevalue
of reaches zero,
Time passed
inThe current
percentage
superheat
superheat
of for
the
this
controller
based on the
will adjust the
the current
each compressor
EXV time defined
EXV based
in the
on the current
state
superheat
status
target setpoint
State Controller in Connect
Additional Circuit Information
Unit Control 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 loaded - all available stages of cooling capacity are on.
UNIT IS LOADED
Chiller is fully unloaded - all stage of cooling capacity are off.
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
Compressor Control States
LOST IO LOCKED
CMP LOCKED OUT
SWITCHED OFF
This state is entered when the Capacity Control State is NO RUN- I/O LOST.
The compressor is in a lockout state
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 Control States
LOCKED OUT
EXV IS CLOSED
PRE-PMPDWN
EXV IN STARTUP
EXV AT 100%
EXV IS HOLDING
EXV IS OPENING
EXV IS CLOSING
LOW SPRHT
OPENING 4x
OPENING 2x
LO PSI OPN
CLOSING 2x
CLOSING 4x
HI LVL CLS
EXV MOP CLS
EXV MOP HLD
The compressor is in a Lockout state.
The associated compressor is OFF and the valve is closed
The valve has been in a closed state and the system is now requiring the valve action.
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.
This state will be entered when the valve opening reaches 100%.
Refer to EXV Logic Chart, superheat is in control zone and ROC is acceptable.
Refer to EXV Logic Chart, superheat is in control zone but rising too fast, ROC less than 1.0.
Refer to EXV Logic Chart, superheat is in the control zone and the rate of change is acceptable,
ROC greater than –0.5.
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.
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
“HiRefLevel” is active and the superheat is greater than the value of this Setpoint.
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.
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
Unloader(s)
the relay turning ‘On
or Off’
Hot Gas Bypass
Fixed Step Capacity
100%
Capacity
75%
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%
Capacity
75%
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
Controling In The Zone
Above the zone
48
47
In the zone
In the zone
Degrees (F)
46
45
Target
44
Control Zone
43
42
41
Time (seconds)
Below the
zone
Chiller Control Decision Making
Set points establish target / control zone
How far from the target setpoint is current control
sensor value
How fast is it 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
Leaving liquid temperature
Suction PSI
Controlling sensor’s rate of change (ROC) is calculated
Rate of Change
120 miles
120
miles
5 hours
5 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 60s)
Setpoints #27 & #28 define the speed limits for the change
in temperature
Negative Rate Of Change
Positive Rate Of Change
300
300
200
200
100
100
0
0
0
5
10
0
5
10
Applied Rate of Change Logic
Control above the zone
Unit Control Starts
in LOADING
Current ROC > MAX ROCUnit Control
Capacity
Controlcontinues
Above the Zone
LOADING
Current ROC ≈ MAX ROCUnit Control HOLDS
54
Degrees (F)
52
50
48
Current Value
46
Target
44
Control Zone
42
40
0
5
10
15 20 25 30
Time (seconds)
35
40
45
Applied Rate of Change Logic
Control in the zone
In Control Zone
Max ROC- < ROC < MAX ROC+
Unit Control is HOLDING
In Control Zone
Current ROC < MAX ROC-
In Control Zone
Current ROC > MAX ROC+
Unit Control starts
UNLOADING
Capacity Control In Zone
48
Unit Control starts
LOADING
47
Degrees (F)
46
45
44
Current
43
Target
Control Zone
42
41
40
0
10
20
30
40
Time (seconds)
50
60
Applied Rate of Change Logic
Control below the zone
Capacity
the Zone
CurrentControl
ROC < Below
MAX ROC+
Unit 50
Control Starts
UNLOADING
Unit Control continues
UNLOADING
47
Degrees (F)
Current ROC ≈ 1°F/s
Unit Control HOLDS
44
Current Value
Target
41
Control Zone
38
35
0
5
10
Time (seconds)
15
20
MCS Safeties
The MCS-Magnum is designed to take corrective action to
prevent a safety from occurring.
The MCS-Magnum checks for safeties every second.
Safeties can apply to the entire package or individual
circuits.
If a safety does occur, the system will:
generate an alarm message
shut the circuit or package down
attempt to restart (after a period of time)
Note, time is unique to each safety.
If the same safety trips within a period of time a lockout
will be created
MCS Safeties
ITEM
VALUE
TIME
SAFETY
LOCKOUT
HI DISC PSI
HDISC P UNLD
HDISC RELD
360
20
40
2 SEC
-
YES
-
YES (2X - 2HRS)
- (AS REQD)
- (AS REQD)
LO SUCT PSI
LSUCT P UNLD
LSUCT P RELD
UNSAFE SUCT
55
1
3
10
90 SEC
3 SEC
YES
-
YES (2X - 2HRS)
- (AS REQD)
- (AS REQD)
YES (1 TIME)
MCS Safeties
ITEM
VALUE
TIME
SAFETY
LOCKOUT
HI DISC TMP
HDISC T UNLD
HDISC T RELD
215
2
5
10 SEC
-
YES
-
YES (2X - 2HRS)
- (AS REQD)
- (AS REQD)
HI AMPS
LOW AMPS
110
20
10 SEC
10 SEC
YES
YES
YES (2X - 2HRS)
YES (2X - 2HRS)
LOW OIL DIFF
UNSAFE OIL
70
15
45 SEC
3 SEC
YES
-
YES (2X - 2HRS)
YES (1 TIME)
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”
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
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 required up to a
maximum (SP 30 & 31)
Training Class Exercise 2
Simulate a High Amp Unload
When the Amps of the compressor reach half
the value of SP ‘HI AMPS % it will start to
unload
If the HI AMPS % (SP 75) is 115
Start unloading begins at 107.5%
Safety occurs at 115% of the FLA
If FLA of compressor 1 (SP 171) is 102 then
adjusting the amps between 109 and 116 will
start unloading the compressor
Questions?