Is Your Boiler Conductivity Sensor Working?

Lakewood Instruments boiler conductivity sensor

What do you do when your boiler conductivity sensor is not giving you the right reading? There are a few simple things you can check to determine whether your sensor is the problem or if something else is going on.

Quick Controller Checks:

  • If your controller is in sample/cycle mode, the conductivity is only measured during the sample part of the cycle. Check what mode you are operating in!
  • The Cell Constant should be set to 0.108 for a boiler– this is a mathematical setting to ensure the controller is looking for the correct input. System Settings>Process Parameters>Cell Constant.
  • Initialize Calibration – this can clear “bad” calibration data that can mess things up. System Setup>Initialization>Calibration.

Checking the Sensor:

Starting at the boiler conductivity sensor, remove it from the system (careful, the system is under pressure!) A visual inspection of the sensor should indicate there are no loose items – all the threads should be tight. If the assembly is loose, it likely means someone used a wrench improperly on the sensor and sorry – there is little that can be done from that point forward as the seals can be compromised. You should also see clean sensor tips with no scaling or debris – if they are dirty, clean them!  Use a soft steel brush (not brass or copper.)

If the physical integrity seems OK, then dry off the sensor tips, and note the reading on the controller. The conductivity should be essentially 0 – because there is nothing conducting electricity between the sensor tips. Then take your screwdriver and short out the process tips – and the controller should react with a very high conductivity.

Remove the wires from the conductivity sensor altogether. To finish testing the sensor, connect an ohmmeter to the standoffs (what you removed the wire from) on the sensor. The resistance should be very high – indicating an open circuit. If you are getting any resistance value, it would indicate you have water inside the sensor body, and the sensor should be replaced.

Checking the Wiring

If the sensor seems OK, then short out the wires themselves – connect them to one another. The controller should react with a very high conductivity. When the wires are separated (not shorted), the controller should read 0 conductivity.

You can also check the controller itself by removing the terminal block connection and then shorting the two pins on the terminal strip – you should see the same controller response as described above.

These steps should help you determine whether the problem is in the controller, the wiring or the sensor itself. If all components are working correctly, then the issue may be in the plumbing layout, flashing or in the system itself.  Call Lakewood, we have a few more tricks up our sleeve to help you out.

A properly installed controller, boiler conductivity sensor and plumbing can give great service for many years if the sensor is cleaned MONTHLY.

As always, don’t hesitate to contact us with any questions!