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II. Description
Control Functions
Each of the control functions is based on an analog input from a probe and will include user settable relay
control settings along with a High and Low Alarm setting and Limit Timer. Each control function will include
a control relay output. When the reading reaches the Set Point the control relay is activated until the
reading changes by the Differential amount.
1.
Conductivity
- The conductivity function of the controller is designed to monitor and control
Total Dissolved Solids (TDS) in a recirculating system like a cooling tower in terms of electrical
conductivity measured in MicroSiemens/cm. This control function is also referred to as bleed. Units
with conductivity and the make-up conductivity function can control the TDS of the tower system
to a cycles of concentration by calculating the difference between the incoming make-up water’s
conductivity and the system’s conductivity
2.
pH
- The pH function monitors and controls pH on a scale of 0-14 pH units.
3.
ORP
- The ORP function monitors and controls ORP on a scale of +/- 999 mV.
Chemical Feed Timers
Selectable Chemical feed timers (base function F) are designed to automate the addition of various
chemicals by activating a relay output. Multiple timers can be supplied depending upon the model number
and each timer will include a relay output. All timers can be programmed to be one of the following types.
1.
Pulse Time
- This timer accepts dry contact pulses from a make-up water meter (supplied
separately). It can accumulate 1-99 pulses to activate the timer to run from 0-99 minutes in minutes
and seconds.
2.
Feed with Bleed
- This timer activates the relay output simultaneously with the bleed. The timer
can limit the amount of time the relay output will be on during the bleed cycle, thereby preventing
chemical overfeed.
3.
Feed after Bleed
- This timer activates the relay output based on a user defined percentage of
the bleed off time. The relay is activated after a bleed cycle and runs for the set percentage of that
bleed cycle. A limit time can also be set for the maximum amount of time the timer can run for one
cycle.
4.
Percentage
- The relay is on for a percentage of a continuously repeating cycle time. The percentage
timer can be set from 1 to 99% and the cycle time can be set from 1 second to 99 minutes and 59
seconds.
28-Day Feed Timers
28-day feed timers, typically used for biocide feed are based on a 28 day cycle with two independent
programmable feed cycles allowing for feed on selectable days and weeks. The biocide timers also
include prebleed and bleed lockout settings. Multiple timers can be supplied depending upon the model
number and each timer will include a relay output.