Walchem 300/400

How do I add 4-20mA output to my W300 series controller?+

W300 controllers can be ordered with a 4-20mA option board factory installed by specifying it in the model code. This option board (p/n190744) can also be installed in the field by simply plugging it into a header. With the exception of a screwdriver used to open the front panel, no tools are required to actually install the board.

The separate option board (p/n 190744) may be installed in the field by plugging into the connector on either the power supply board and/or the front panel board. The instruction manual for your particular controller will provide the details on where the option board may be installed. When the controller is powered up again, the menus for the 4-20 mA output will appear.

CAUTION: There are live circuits inside the controller even when the power switch on the front panel is turned OFF. The front panel should never be opened before power to the controller is REMOVED.

Why does the controller overshoot the set point?+

A. Pump is too large: Calculate the flow rate required. The metering pump should be set for no more than 1.5 times the expected depletion rate of the chemical. Either adjust the flow rate of the pump down to this level, or replace the pump with one that better matches the required flow rate.

B. Pump is siphoning: Install anti-siphon valve on metering pump, or on metering pump discharge line. Avoid down hill" tubing runs. A metering pump injecting into open atmosphere can pump more than its rated capacity if an injection check valve is not installed.

C. Poor mixing/large lag time: Improve mixing or move the location of the sensor and/or replenishment so that chemical additions reach the sensor faster. If using a flow-through sensor make sure that the flow rate through the sampling system is sufficient (less than 1 minute to detect additions). If the lag time can't be improved then in pH/ORP applications a proportional controller should be used. For other applications it may be possible to use the optional 4-20 mA output for proportional control.

D. Fouled sensor: If the response time of the sensor to a step change in concentration is slow then the sensor may need to be cleaned calibrated or replaced. Follow the sensor troubleshooting instructions for that particular sensor.

E. Programmed incorrectly: For on/off controllers make sure the value of the dead band menu is not too large. For proportional controllers increase the value of the proportional band menu.

F. Relay stuck closed: Use the "Hand-Off-Auto" menu to control the relay. If an ohmmeter doesn't show the contact opening and closing then replace the power supply board or have the unit serviced by the factory.

How far can I run the electrode cable?+

For the most reliable installation, the cable length should be as short as possible. The absolute maximum cable length is 500 feet. Proper shielding of the cable is essential to reliable performance. Four conductor, 24 AWG, shielded cable should be used.

Can I connect a flowmeter to your cooling tower or boiler controller?+

The single input controllers (WCT/WBL) can power a hall effect sensor with 5 VDC; By moving a jumper, they can also read the high frequency paddlewheel signal. Programming it to feed based on a paddlewheel gives you the ability to set the K factor.

Dual input controllers (WDT/WDB) have the ability to power ONE hall effect sensor, on the main (A channel) board only, and the programming does NOT support a paddlewheel on either the A channel or the B channel.

Can I use your controller for boilers with pressures exceeding 250 psi?+

While our boiler electrodes are rated to 250 psi, they can be used in higher pressure boilers if a sample cooler is incorporated into the blowdown skimmer line. This method of installation is preferred even in lower pressure applications, since it eliminates potential problems related to flashing, and improves safety.

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