may be feature differences between the two systems on a unit with two systems. (See
model numbering table on page 3.)
Control Functions
Each of these control functions are 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 or boiler in terms of electrical conductivity measured in MicroSiemens/cm.
This control function is also referred to a Bleed. Units with conductivity and the
make-up conductivity function can control the TDS of the tower system 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 +/- 1000 mV.
Chemical Feed Timers
Chemical feed timers 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 pulses from a make-up water meter (supplied
separately). It can accumulate 1-99 pulses to the 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. This timer limits 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 time the bleed off. The relay is activated after a bleed cycle and
runs for the set percentage of that bleed cycle.
4.
Percentage
– The relay is on for a percentage of a continuously repeating cycle
time. Both the percentage and cycle time are programmable.
5.
28 Day
– The timer is based on a 28 day cycle with two independent
programmable feed cycles with prebleed and bleed lockout settings.
4