Liquitron DC4500 Series Instruction Manual

LMI Liquitron Series DC4500 Instruction Manual

LMI Liquidtron Controller
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Click on links below for Instructions:

1.0 Introduction
2.0 Installation
2.1 Mounting the Controller Enclosure
2.2 Enclosure Mounting Dimensions
2.3 Electrical Wiring Information
2.4 Terminal Strip Layout
3.0 Operating the Controller
3.1 Menu Overview
3.2 Conductivity
3.3 Set Point
3.4 ∆ Differential
3.5 Low Alarm
3.6 High Alarm
3.7 Feed
3.8 Clock
3.9 View Biocide
3.10 Add Biocide
3.11 Biocide Lockout
3.12 Biocide Prebleed
3.13 Manual Outputs
3.14 Advanced Setup
3.15 Temperature
3.16 H2O Meter
4.0 Start-Up
4.1 Cooling Tower Installation
4.2 Cooling Tower Start-Up
4.3 Bleed Sampling Option
5.0 Calibration
6.0 Maintenance
7.0 Troubleshooting
8.0 Factory Settings
9.0 Product Specifications
10.0 Product Exploded View
11.0 Product Parts List

Introduction Liquitron DC4500 Controller

The DC4500 is a microprocessor-based conductivity controller. It is designed for use in a variety of water treatment applications requiring precise control of totally dissolved solids and chemical feed. Among its many uses, the DC4500 will control conductivity and chemical feed in cooling towers and closed loop systems.

LMI’s DC4500 Series of conductivity controllers allows the greatest programming flexibility for cooling tower system applications. This is accomplished through the use of an extensive options menu that is easy to use.
BLEED or BLOWDOWN of system water by valve control can be based on several setpoint options:

  • Conductivity setpoint
  • Hysteresis delay (lower than setpoint) to avoid valve operation chattering
  • Rising or Falling conductivity trip points

FEED of chemical (inhibitor) can be based on four (4) different methods and the pump control can be either On/Off or externally-triggered Variable Speed.

  • FEED at the same time system BLEEDS (lockout timer limits maximum FEED time)
  • FEED time calculated as a percentage of total BLEED time
  • FEED based on a timed cycle (pump is on for a percentage of this timed cycle)
  • FEED based on flow meter input

DUAL BIOCIDE chemical addition may be accomplished by the use of two (2) individually programmable relays or optocoupler outputs. These outputs provide control of two individual chemical addition pumps based on the following options:

  • On/Off or externally-triggered Variable Speed pump control or BOTH for two pump/TIMER operation
  • 28-DAY programmable timer (1, 2, 3, or 4 week selectable cycle)

ALARM indicators and relay outputs are energized based on the following conditions:

  • HIGH conductivity set point is reached
  • LOW conductivity se tpoint is reached
  • NO FLOW condition exists (flow switch must be installed)

The display is a 16-character backlit LCD (liquid crystal display) which is visible in all light conditions. A three-key position membrane is used to enter data and settings (see Figure 1). The conductivity range is 0 – 20,000 µSiemens. The units can be either µSiemens or PPM/TDS (total disolved solids).

All setpoints and parameter settings are retained permanently in a special nonvolatile computer chip memory, preventing their loss due to a power outage. This nonvolatile memory chip allows the unit to be programmed before installation. No battery powered backup is required. Built in test circuits are provided to test each individual relay output wiring and to allow for quick field service isolation of faulty probe, circuit cards, pumps, or solenoids for ease of troubleshooting. A display for temperature is also provided. The range is 32° F to 158° F [0° C to 68° C]. The display can be either fahrenheit or centigrade. This reading also provides the basis for temperature compensation which is performed in all modes.

Liquitron Display Descriptions
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An analog data (or control) output is provided. This is a non-isolated 4 – 20 mA signal. The conductivity reading that corresponds to minimum and maximum analog signals is fully adjustable. This signal can be used to power chart recorders or other pumps and devices.

The controller operates in two (2) distinct modes, ‘SYSTEM RUN’ and ‘SYSTEM START-UP’ or ‘PROGRAMMING MODE’. The unit will be in the ‘SYSTEM RUN’ mode when it is first turned on. The various program screen menus are used to calibrate the unit, set the control and alarm points, set the inhibitor feed operating parameters, program the biocide [two (2) chemical addition] pumps, and manually test the relays and wiring connections.

In the ‘SYSTEM RUN’ mode the DC4500 monitors the conductivity and activates the appropriate control or alarm relay as necessary based on the set points entered in the ‘SYSTEM START-UP’ mode.

The DC4500 is packaged in a NEMA 12X, flame-retardant, molded TPE enclosure. When ordered, 115 VAC units come fully wired to include input power cord and relay output pigtails to allow for simple installation. The unit can be hardwired through conduit to the lower junction box portion of the enclosure when required. Hard wiring makes the unit suitable for NEMA 4X applications.

Mounting the DC4500 Controller Enclosure

The DC4500 conductivity controller is supplied with integral wall-mounting flanges.  It should be mounted with the display at eye level on a vibration free surface.  All accessible  mounting holes should be utilized.  The maximum allowable temperature is 122° F [50° C].  This should be considered if installation is in a high temperature location.

Once the DC4500 is wall mounted, the metering pumps may be located at any distance from the controller.  The conductivity probe should be placed as close to the controller as possible, to a maximum distance of 300 ft [91 m].

Under 25 ft [7.6 m] is recommended.  Over 25 ft [7.6 m], the cable may need to be isolated or shielded from background electrical noise.

DC4500 Controller Enclosure Mounting Dimensions

When using the prewired unit, the enclosure is configured as NEMA 12X. If the unit is connected through watertight conduit, the enclosure is configured as NEMA 4X.

The following clearances should be observed for proper mounting (see Figures 2 and 3).

Liquitron LMI Enclosure
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Liquitron DC4500 Electrical Wiring Information

LMI Controller

To reduce the risk of electrical shock, the controller must be plugged into a grounded outlet with ratings conforming to the specifications on the data nameplate. It must be connected to a viable ground circuit. DO NOT USE ADAPTERS (see Figure 4)! All wiring must conform to required electrical codes.

Caution LMI Plug Instructions
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The DC4500 conductivity controller is available in either 115 or 230 VAC 50/60 Hz. The 115 VAC version is supplied with one (1) 6-foot grounded AC power cord and four (4) 12-inch output pigtails for plug-in connection of controlled devices.
A four-pin connector is provided for the conductivity probe and temperature compensation probe.

The DC4500 controller is provided with a voltage selector switch to allow the unit to be used with a 115 VAC or 230 VAC power source.  To change the voltage selection, disconnect the unit from the power source and remove the front keypad panel.  The selector switch is located on the circuit board attached to the back panel. When switching voltages ensure that power cord and pigtails are appropriately changed

Operating the DC4500 Controller

The Conductivity Read Screen or System Run:

dc4500 controller display

The normal operating display for the DC4500 Series Controller is the conductivity reading screen as (shown above). This screen is referred to as “System Run” throughout this manual. The screen will alternate between the conductivity reading and the day and time display. The controller relay outputs cannot be activated unless the unit is in the “System Run” or conductivity reading mode. The only exception is when the unit is in the test mode.

After reviewing or changing the conductivity controller programming setpoints, the unit must be returned to the “System Run” or conductivity reading screen to allow automatic control to proceed. There are three ways to return to the “System Run” screen and mode:

  1. Use the
    Controller Up Key
    Controller Down Key
     keys to move through the various menus, and back to the “System Run” screen.
  2. Push ANY two (2) keys simultaneously. This will return the unit immediately to the “System Run” screen.
  3. The unit will return to the “System Run” screen automatically after three (3) minutes if no keys are pressed.

DC4500 Controller Conductivity

Screen Display dc4500

Conductivity Reading Screen

The “CONDUCTIVITY” screen displays the conductivity readings in either µSiemens or PPM/TDS (parts per million/total dissolved solids). When the controller is displaying this screen it is considered to be in the SYSTEM RUN mode. This means that the pumps, solenoids, and alarm outputs will be activated based on the controller’s programmed set points. When the controller is in any other display screen all the outputs are disabled and will not be energized.

From Conductivity Screen….press Enter….to access Calibration From

Pressing the “ENTER” key when the “CONDUCTIVITY” screen is displayed accesses the calibration mode. From this “CALIBRATION” screen the “UP” or “DOWN” keys can be pressed to change the conductivity reading and adjust for inaccuracies. If calibration adjustment is attempted beyond 50% of the probe conductivity reading, the controller will flash a warning on the screen: “CALIBRATION LIMIT”. This alerts the operator that the probe needs to be serviced.

DC4500 Set Point Screen

DC4500 Controller
LMI Controller Menu

Set Point Screen

The “SET POINT” screen allows access to the conductivity value that will energize the bleed output relay and allow for the opening of the bleed valve. The output trip setting may be changed in this screen. The relay can be programmed to respond to either rising or falling conductivity values (see “ADVANCED MENU” options under “TRIP”).

DC4500 Menu

Pressing “ENTER” from the main menu “SET POINT” screen accesses the conductivity reading trip value and allows the value to be changed. The value will have a flashing cursor indicating that it can be changed. Press the “UP” or “DOWN” key to increase or decrease the value. Press “ENTER” to save the value.

DC4500 Differential Screen

DC4500 Menu list
Differential Dead Band

Differential or Dead Band

The “DIFFERENTIAL” or dead band setting allows for a hysteresis to be programmed in to the conductivity trip point. A programmed hysteresis value prevents the bleed relay and solenoid from cycling on and off repeatedly when the conductivity reading hovers around the trip set point. The value entered in the “DIFFERENTIAL” is the amount of conductivity, away from the trip “SET POINT”, that the bleed relay will shut off.

LMI Controller Setting

Press “ENTER” from this screen to change the value. The value will have a flashing cursor indicating that it can be changed. Press the “UP” or “DOWN” key to increase or decrease the value. Press “ENTER” to save the “DIFFERENTIAL” value.

DC4500 Low Alarm Settings

LMI Controller Setting
Liquitron Alarm

Low Conductivity Alarm Set Point

The “LOW ALARM” screen allows programming of the Low Conductivity reading that activates an alarm LED and output relay.

LMI Controller Setting

Press “ENTER” from “LOW ALARM” screen to change this value. The setting will have a flashing cursor indicating that the value can be changed. Press the “UP” or “DOWN” key to increase or decrease the setting. Press “ENTER” to save the value.

DC4500 High Alarm Setting

Menu List DC4500
DC4500 Display setting

High Conductivity Alarm Set Point

The “HIGH ALARM” screen allows programming of the High Conductivity reading that activates an alarm LED and output relay.

LMI Controller Conductivity setting

Press “ENTER” from “HIGH ALARM” screen to change this value. The setting will have a flashing cursor indicating that the value can be changed. Press the “UP” or “DOWN” key to increase or decrease the setting. Press “ENTER” to save the value.

Liquitron DC4500 Feed Settings

DC4500 Controller Feed
Controller Menu Item

Feed Pump Screen

The “FEED” screen displays the current Inhibitor Feed Pump mode selected. There are four different FEED modes that may be selected from. The current active mode is displayed in parenthesis. The four possible modes to select from are:

LMI Controler Menu Instructions

Pressing the “ENTER” key from the main menu screen “FEED” ( Mode ) accesses the FEED sub-menu selections. Use the “UP” or “DOWN” key to scroll through the four different modes.

LMI Controller DC4500
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When the mode desired is displayed on the screen press “ENTER” to access the particular settings for that mode. The variables and settings that are available for each option are shown above.   Use the “UP” or “DOWN” key to change the settings and press “ENTER” to save that setting.

DC4500 Clock Settings

Settings Clock Liquitron
Program Clock Liquitron

The “CLOCK” screen displays the current week, day, and time. The time is based on a 24-hour clock. The number week that is displayed reflects the current week during the selected biocide programming based on a 1, 2, 3, or 4 week repeating cycle.

dc4500 Set clock

Pressing the “ENTER” key from the “CLOCK” screen accesses the various clock settings. The first screen displayed is the BIOCIDE cycle screen. The BIOCIDE cycle reflects the number of weeks that repeat in the BIO 1 and BIO 2 programming. For example, if a twoweek repeating biocide pumping cycle is desired, then a “BIO WEEK = 2” would be selected. The “weeks” may be selected to be a 1, 2, 3, or 4 week repeating cycle. A cursor will be flashing in this screen to indicate the value may be changed. Press the “UP” or “DOWN” key to change the value.  Press “ENTER” to store the value and to move to the next “CLOCK” setting screen. The next screen is the “WEEK” setting Screen. This is the week that the clock is currently running in. Again,  press the “UP” or “DOWN” key to change the value and “ENTER” to save.The next screen displayed is the “DAY” screen. Pressing the “UP” or “DOWN” key changes the setting and pressing “ENTER” saves the selection and moves to the “HOUR” screen. Pressing  “UP” or “DOWN” changes this value and pressing “ENTER” saves this value and moves to the “MINUTE” screen.  Pressing “ENTER” from the “MINUTE” screen returns to the “CLOCK” display screen

DC4500 View Biocide Setting

DC4500 Controller Setting
Liquitron Menu

Review Current Programmed Biocides

The “VIEW BIOCIDE” menu screen allows the operator to review the list of the programmed Biocide pump “on” times. This list is for ALL programmed Biocides (both Biocide 1 and Biocide 2). Press “ENTER” from this main menu screen to access the list of biocide pump “on” times. The list of “on” times is presented in the numeric order of the Week first and then the Day . For example, a programmed pump “on” time for week “1” will be listed before a pump programmed for week “2”. A programmed pump “on” time for week “1” “Monday” will be listed before a pump programmed for week “1” Wednesday.

Instructions Controller

The screen display for each of the programmed pump “on” times appears as shown above. The first alpha/numeric group “B1” represents the BIOCIDE selected (Biocide 1). The second group “W4” represents the WEEK selected (Week 4). The third group “MON” represents the day selected (Monday). The fourth group “15” represents the HOUR selected for the pump to turn on (based on a 24-hour clock). In this example, the pump is programmed to turn on at hour 15, or at 3 o’clock in the evening. The fifth group “55” represents the duration of time that the pump will remain running. In this example the pump will run for 55 minutes. Based on the above example, biocide pump #1 is programmed to turn on at 3:00 pm for 55 minutes during week 4 on Monday.

view Biocide Instructions
Click image to go to Larger Diagram

DC4500 Add Biocide

Controller Menu DC4500
LMI Controller Display

Biocide pump “on” times may be programmed or added in this main menu selection screen. Press “ENTER” to access the sub-menu screens that allow the programming options for each Biocide pump. Once in these sub-menu selection screens, press the “UP” or “DOWN” keys to change each one of the values. The values that may be changed will have a flashing cursor. Press the “ENTER” key to save that value and move to the next sub-menu screen.

Liquitron DC4500 Instructions
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DC4500 Series Biocide Lockout

DC4500 Menu List
LMI Controller Screen

The “BIOCIDE LOCKOUT” screen selection allows for the programming of a system Bleed lockout time. This option prevents the bleed of a cooling tower immediately following chemical biocide addition. Press “ENTER” to access the “LOCKOUT” screens where this option is programmed. The number of minutes that the bleed function needs to be disabled can be varied as required. Each Biocide pump lockout time can be individually programmed.

DC4500 Instruction Manual
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DC4500 Biocide Prebleed Instructions

DC4500 Controller List
Liquitron Display

Biocide Prebleed Screen

The Biocide pump “PREBLEED” option is available in order to bleed down the cooling tower to below conductivity limits prior to biocide chemical addition. This option is pragrammable in one of two modes. The prebleed may be selected for either a programmed amount of time or a conductivity set point. If the time option is selected,  then the cooling tower will be bled down for that programmed amount of time prior to the biocide pump “on” time. If the conductivity set point is selected, then the cooling tower will be bled down to this set point prior to the biocide chemical addition. This set point prebleed starts at the programmed biocide pump “on” time. The biocide pump will come on after this conductivity point has been reached.

LMI Controller Instructions
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DC4500 Manual Outputs Operation

DC4500 List LMI
Programming DC4500

Manually Energize Relay Outputs

The “MANUAL OUTPUTS” mode is provided to allow for manual energizing of each relay output. Once the external devices have been connected, they may be individually or collectively energized and tested. Testing of all these components is recommended after system installation and prior to system start up. Press “ENTER” to access these sub-menu screens. Press the “UP” or “DOWN” key to move to each relay control screen. Press “ENTER” from each relay output screen to energize that output relay. Press “ENTER” a second time to de-energize that relay. One or all of the relays may be energized in this manner. The output relays will be de-energized if:

  1. No Keys are pressed for 3 minutes and the controller returns to the “system run” screen.
  2. The operator manually de-energizes each relay output.
  3. The operator manually exits the “MANUAL OUTPUT” sub-menu screens
Manual Outputs Instructions
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DC4500 Advanced Setup Instructions

DC4500 List Options
DC4500 Menu Screen

The “ADVANCED SETUP” screens allow for the special configuring of the controller for advanced options. These options include:

  • FLOW ALARM (energizing the alarm output relay on loss of flow);
  • FLOW SENSE (under FLOW ALARM the response of the flow switch may be changed from either normally open or normally closed logic);
  • TRIP (bleed based on either rising or falling conductivity trip point);
  • 4 – 20 mA recorder output programming, conductivity units DISPLAY may be either µSiemens or PPM/TDS;
  • PULSE OUTPUT (strokes per minute programming control of each individual pump);
  • FEED LOCKOUT (prevents feed pump from operating during biocide addition);
  • BLEED control (continuous or timed);
LMI Controller Operations Manual
Click image to see larger Diagram

DC4500 Temperature Controls

List Options Controller
LMI Controller Display

The “TEMPERATURE” screen displays the temperature sensed by the externally connected thermistor [10K Ohms at 77° F / 25° C]. The screen may display temperature in either Degrees (F) or Degrees (C). Pressing “ENTER” from this screen accesses this option change. Pressing the “UP” or “DOWN” key toggles between displaying °F or °C. Pressing “ENTER” a second time saves the displayed Temperature selection.
LMI Controller Setting
DC4500 H2O Meter Programming Instructions

LMI Controller List Options
LMI Controller Display

Water Meter Totalizer Screen

The “WATER METER TOTAL” screen allows for the display of the total gallons accumulated through a flow meter. The submenu’s allow for the programming of the: 1) counts-to-gallons ratio; and 2) reset of the totalizer.

LMI Controller Instructions
Click image to see larger diagram

DC4500 Cooling Tower Installation Instructions

The DC4500 Series of conductivity controller should be installed based upon the recommended system diagram below. A bypass loop for open recirculating water systems is the best method of conductivity monitoring and control.

The conductivity sensing electrode used with the conductivity controller must receive an active representative sample of system water. The electrode should be installed so that it is removed horizontally from its mounting tee. Water flow should enter from the bottom of the conductivity tee and exit out the top. This type of installation insures that the electrode tee is full of water whenever system flow is on and that the probe is fully immersed. This prevents the electrode from becoming air bound.

System shut off/isolation valves are recommended for installation on either side of the conductivity sensing electrode. This allows for ease of system isolation and electrode removal. A sample cock valve and a strainer are recommended to allow for periodic water sampling and water filtering.

Injection of required water treatment chemicals can be effected directly into the bypass line. When chemicals are injected into the bypass line, they should be downstream of the conductivity sensing electrode to avoid interference with readings.

An installed flow switch is recommended for the bypass line to allow for disabling of controller/pump operation during system maintenance or repair.

LMI Controller Instructions
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DC4500 Cooling Tower Start Up

If you prefer, you can download this PDF as a working document for  DC4500 Cooling Tower Worksheet

The DC4500 can be programmed for a multitude of tasks for cooling tower applications.  Prior to powering up the DC4500 Conductivity Controller it is recommended that the following PRE-START UP work sheet be completed to determine required system operating parameters.

1.- Current System Conductivity __________________________________________________

2.- Desired Conductivity Set Point _________________________________________________

3.- Differential (Hysterisis) Range _________________________________________________

4.- Method of Chemical Inhibitor Feed (choose one of the following) __________________________

  1. PULSE TIMER (Flowmeter based input response).
  2. % of TIME (Continuous repeating cycle with pump ON time based on percent of the  cycle time.
  3. % of BLEED or BLOWDOWN (Amount of feed is based on a percent of the total bleed/ blowdown time).
  4. LIMIT (Chemical inhibitor feed at the same time as system bleed or blowdown).

The Feed pump can be controlled by either a powered relay output or by direct  variable speed control.  The direct power or On/Off mode requires the pump to be  connected to the ‘FEED L’ and any ‘AC NEUT’ terminal connection on the pc board.  If an LMI ‘7’ or ‘9’ series pump is being used the pump stroking speed may be  directly controlled by the DC4500 pulsed output.  The pump 4 pin connector must  be wired to the ‘PLS1 +’ and ‘PLS1 -’ terminals on the pc board.

On/Off Pump Control __________________________________________________
Variable Speed Pump Control _____________________________________________

5.- High Alarm Setting _____________________________________________________

6.- Low Alarm Setting ______________________________________________________

7.- Flow Switch Alarm activation (Yes/No) ________________________________________

8.- The DC4500 controller can be configured to control dual-chemical (biocide) pumps for water contamination/biological growth control based on a selectable 1-4 week timer. Use the table below to assist in setting up the program operating periods for the pumps when using the 1-4 week timer option.

LMI Controller Timetable

The Biocide chemical pumps may be controlled by either On/Off or Direct Variable Speedmodes. The On/Off mode supplies AC power to the pump based on relay control. The Direct Variable Speed Control mode supplies a low voltage signal to the pump for pump stroke rate control.

The terminal connections on the I/O pc board for these modes are shown:

LMI Controler Biocide Setting

9.- Biocide Lockout Timer ____________________________________________________

10.- Biocide Pre-Bleed Timer ___________________________________________________

11.- 4 mA Output ___________________________________________________________

12.- 20 mA Output __________________________________________________________

Once the operating settings and parameters have been determined by the data entered in the previous pages, the DC4500 Controller can then be programmed. Supply power to the controller. Read the conductivity and verify the accuracy using a calibrated meter and conductivity sample. Calibrate the controller as needed. See Calibration Section.

In the Main Menu, enter the required values for Conductivity, Differential, Low Alarm and High Alarm.

Go to the FEED menu screen (see FEED programming sheet in manual) and enter the required mode and settings for the chemical inhibitor pump control.

Go to the SET UP menu screen (see SET UP programming sheet in manual) and enter the Flow Alarm Option, Trip Actuation, 4 – 20 mAmp settings, Display Mode, Pulse Output Pump Control, and Control Cooling Tower.

Go to the CLOCK menu screen (see CLOCK programming sheet in manual) and enter the current day and time information as well as the number of weeks required for the repeating Biocide Pump programming.

Go to the BIOCIDE pump menu screen (see BIOS programming sheet in manual) and enter the required options for the Biocide Pumps.

Use the MANUAL OUTPUTS menu (see MANUAL OUTPUTS programming sheet in manual) to check that all controlled devices are properly connected.

This completes the cooling tower start-up.  Return the display to the ‘SYSTEM RUN’ or ‘CONDUCTIVITY Reading screen to begin operation.

The system will return to the “SYSTEM RUN” mode automatically on its own after three (3) minutes if no keys are pressed.

If you prefer, you can download this PDF as a working document for  DC4500 Cooling Tower Worksheet

DC4500 Bleed or Blowdown Sampling Option

Operating Mode

The DC4500 Conductivity Controller can be configured to operate in one (1) of two (2) different operating modes for conductivity bleed or blowdown:

  1. Timed Conductivity Blowdown Sampling
  2. Continuous Conductivity Blowdown Sampling (Standard Method)

The Continuous Conductivity Bleed/Blowdown is the most commonly used method. When the conductivity is above a setpoint, a valve is opened and water is bled off until the conductivity is below the setpoint minus the hysteresis. All DC4500 Controllers are factory set for this method of control.

In the ADVANCED Menu, the operator is offered the option of changing this to a “TIMED SAMPLING” method of bleed control.

In the “TIMED SAMPLING” mode, the conductivity is only looked at periodically. If the conductivity is high, the valve will be opened and the water bled off until this conductivity is brought back to the desired setpoint. This is done when the probe is installed on the drain line itself. It allows for minimal piping installation.

The programmed settings for this method are 1) sampling time, and 2) sampling duration.

  • SAMPLING TIME – is the amount of time in between active conductivity readings. If the conductivity is above the setpoint during this time, the unit will not bleed.
  • SAMPLING DURATION – At the end af the Sampling Time, the bleed valve will automatically open up and start bleeding off water. The unit will bleed water off for the entire sample duration time. This is done to get a good clean sample near the probe. At the end of the sample duration the valve will be closed if the conductivity is below the setpoint, or held open if the conductivity is above the setpoint. It will then continue to bleed until the setpoint is reached.

DC4500 Calibration Instructions

Calibration will be required during system start up or when a variation in conductivity readings exists between the displayed conductivity and the conductivity value determined from a reliable source (such as a hand held tester). The conductivity probe should be cleaned prior to calibration (see 7.0 MAINTENANCE for probe cleaning instructions).

The ‘SYSTEM RUN’ or ‘CONDUCTIVITY reading ’ screen is used to calibrate the controller. Press the ‘ENTER’ key from this main menu screen to access the calibration mode. The ‘CALIBRATION’ screen will display the word CAL and then the current conductivity reading. Place the probe in the conductivity standard. Allow the conductivity reading to stabilize. Use the ‘UP’ or ‘DOWN’ keys to enter the correct conductivity reading, and then press enter. This will save the reading value and re-calibrate the controller based on this value.

If the probe reading is off by more than 50%, then the controller will indicate an error by displaying ‘CAL LIM uS‘.  This means that the probe has failed or needs cleaning.

Alternately, a sample of cooling tower water may be analyzed by a precalibrated conductivity monitor, and the DC4500 controller calibrated to match that reading using the sample as a standard solution.

LMI Controller Instructions

The DC4500 Controller provides a circuit board test-switch to aid in troubleshooting the unit and system. The switch is located under the access cover on the lower section of the controller (see Figure 5).

The conductivity test-switch allows the user to determine if the conductivity circuit is operating correctly. When placed in the test position, this switch switches the conductivity probe and wiring out of the circuit and places an internal precision resistor. This resistor has a known conductivity reading of 3000 uS +/- 5%. If the unit has been calibrated then this reading could be displayed as + or – 50% of this 3000 µS value (+4500 µS, -1500 µS).

DC4500 Maintenance Controller and Probe


The DC4500 controller itself requires very little maintenance. Wiping the controller down with a damp cloth will clean it. Do not spray down the controller unless the enclosure door is closed and latched.


The controller must be re-calibrated after cleaning the probe

Cleaning Procedure

The probe can normally be cleaned using a cloth or paper towel and a mild cleaning solution such as 409 cleanser. Occasionally, a probe may become coated with various substances which require a more vigorous cleaning procedure.  Usually the coating will be visible, but not always.  To clean a coated probe, use a fine grit abrasive, such as emery paper.  Lay the paper on a flat surface and move the probe in a back and forth motion as shown in Figure 7. The probe should be cleaned parallel to the carbon electrodes, NOT perpendicular.

Controller Set up


The probe should periodically be cleaned to maintain accurate measurements. The frequency of cleaning required will vary from application to application. In a new installation, it is recommended that the probe be cleaned after two (2) weeks of service. In order to determine the frequency of cleaning, use the following procedure.

  1. Read and record the conductivity with probe in system.
  2. Remove the probe, clean it, and place it back into the system.
  3. Read the conductivity of the probe after it is cleaned and record it.

Compare the first conductivity with the second. If the variance in readings is greater than 5%, increase the frequency of probe cleaning. If there is less than a 5% change in the reading, the probe was not dirty and can be cleaned less often.

DC4500 Oringinal Factory Settings

Conductivity Set point2000 S
Delta Differential100 S
Low Alarm100 S
High Alarm4000 S
Feed ModePulse Timer
Pulse Timer10 seconds
Pulse Count1 flow meter count
% Time – Cycle Time10 Minutes
% Time –10%
Feed after Bleed10%
Feed after Bleed – Limit10 Minutes
Limit (Feed & Bleed)10 Minute Limit
Flow Alarm (On/Off)Off
Trip (Rise/Fall)Rise
4 mAmp setting0 S
20 mAmp setting20,000 S
Display (uS/PPM TDS)S
Pump Pulse Feed100 strokes/minute
Pump Pulse Biocide #1101 strokes/minute
Pump Pulse Biocide #2102 strokes/minute
Controller Cooling Continuous/TimedContinuous
Biocide Lockout0 Minutes
Biocide Prebleed0 Minutes
Biocide Week Cycle4 Weeks

DC4500 LMI Controller Product Specifications

Power Requirements115 VAC +/-15%, 50/60 Hz
230 VAC +/-15%, 50/60 Hz
Voltage input selectable via a selector switch located on the I/O PCB. Fuse: 4A 250 VAC Time Delay
InputsFlow Switch. All low voltage inputs active low, i.e. the active state is when the switch is closed. The switch must be capable of switching 2 mA at +/-15 VDC.
OutputsPulse Pump A and B, Auxiliary, Alarm
 All low voltage outputs capable of switching 2 mA at = 24 VDC. The pulse output frequency range is 0-100 SPM. The pulse output is active low. The pulse width is 100 milliseconds in the active low state.
The output type is an opto-isolated NPN transistor open collector configuration. 4-20 mA: 600 ohms maximum
KeypadThree key membrane keypad with tactile response. Material: Polyester with a hard coat finish. Actuation Force: 2.6N to 3.3N.
Temperature InputThermistor resistance 10k Ohms at 77° F [25° C] Circuit Accuracy: +/- 33° F [+/-0.5° C] Temperature Display: 32° F to 212° F [0° C to 100° C] Temperature resolution: +/- 1.8° F [+/- 1° C]
Probe InputCell constant of 1.5 ESD Protection: 700 Volts Three (3) sample readings / second : display updated every second
RelaysFuse protected electromechanical. Control Relay (1): 250 VAC, 10amp contact relay Feed Relay (1): 250 VAC, 10amp contact relay Biocide Relay (2): 250 VAC, 10amp contact relay Contact type: Normally open and normally closed contacts (FORM C) Change over relay.
LCD Display16-Digit Liquid Crystal Display [LCD] with green backlighting
Operating Temperature32° F to 122° F [0° C to 50° C]
EnvironmentalPrinted pc boards conformally coated.
Enclosure: IEC IP65, NEMA 4X – Door closed. IEC IP NEMA – 12X Door open
MechanicalTwo (2) pc boards [three (3) if communication option installed]. Control CPU board: microcontroller and display – low voltage. Terminal power I/O board: transformer, fuses, terminal blocks, relays. Option board: 4-20 mA output – low voltage.

DC4500 Device Exploded View Diagram

Diagram of LMI Controller DC4500 Exploded View.

LMI Controller Product Diagram
Click diagram to view larger image

DC4500 Product Parts List