ProMinent DCM 2 Series, Installation Manual

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DCM 2 Installation
Page 29
Sensor < Turn OFF Setpoint
Event Rising
[Not normally used in Aquatic
applications]
Rising Setpoint Operates only during
Timed Events Acid Feed or Dechlorination
Event Falling Falling Setpoint
Operates only during Timed Events Oxidant alternate setpoint
Event Between
[Not normally used in Aquatic
applications]
Between Setpoints
Operates only during Timed Events Blocking – sequencing controls.
Frequency Controlled Pumps, Contacts 4 & 5
Sets the variable frequency control range for pumps controlled by sensors A, B or C.
Not applicable to pumps controlled by volume meters or contact set F.
Method Function Examples
Always Frequency varies proportional to sensor
value when value between Turn OFF
setpoint and deadband limit. Proportional acid or oxidant
controls.
Substitutes for more expensive
4-20mA controlled pumps. Can
also select PID control
functions in addition to strictly
proportional control.
During Events Control active during events until event
volume pumped. Periodic flocculent feed during
a timed feed event.
5.3.3. Special Control Responses
Multiple Types of Control For Standard Relays
Time Modulation : Relays 1-5
Application: Cycles a chemical feed pump ON/OFF, decreasing the ON time as the
controlling sensor approaches the Turn OFF setpoint (Turn on + Deadband).
Typically used for pH control, reducing acid feed rate as the Turn OFF setpoint is approached.
Use if you can’t use a variable pulse frequency controlled pump.
Setup: User selects a relay & selects Time Modulation in Special Control.
User sets Period in seconds, minimum 60 (recommended), Default is currently at 120 Seconds,
maximum is 600 seconds.
Operation: Relay ON 100% of Time Period when Control is beyond Turn ON setpoint.
Relay ON time = [ (Control – Turn OFF Setpoint) / Deadband ] x Period
where Deadband = Turn ON – Turn OFF setpoints.
Relay is OFF when Control is beyond Turn OFF setpoint.
Example: Acid Pumps Turn ON = 7.52 pH and deadband of 0.02 pH (Turn OFF = 7.50 pH).
Period = 60 seconds
At pH >= 7.520, Pump ON for 60 seconds in every 60 seconds [100% of Period]
At pH = 7.515, Pump ON for 45 seconds, off for 15 seconds [75%]
At pH = 7.510, Pump ON for 30 seconds, off for 30 seconds [50%]
At pH = 7.505, Pump ON for 15 seconds, off for 45 seconds [25%]
At pH <= 7.500, Pump OFF [0%]