Troubleshooting Boiler Conductivity Sensors

Lakewood Instruments boiler conductivity sensor

The main cause of boiler sensor failure is steam exposure. Our SR2 series sensors, both Standard and Harsh Duty, are not designed for a steam environment. When a boiler plumbing set-up is not optimized, damage to the sensor can be the result. Damage can include burned sensor tips, pitted sensor tips, and failed o-rings.

Burned or pitted sensor tips can inhibit the sensors ability to accurately measure conductivity. If the conductivity read by the controller is not accurate due to the sensor, the controller’s performance suffers greatly. Typically, in a properly plumbed system, this is caused by insufficient flow restriction. A lack of flow restriction will cause steam flash. Steam flash will eventually destroy a sensor.

A second cause of boiler sensor failure is chemical reaction. If your boiler has a high amine content, chances are that the standard sensor will fail before its time due to a failure in the o-rings and seals of the sensor. When high amounts of amines are used, we suggest the use of the Harsh Duty (HD) sensor. This sensor contains amine-resistant o-rings and seals and will last much longer in a harsh chemical environment.

The next probable cause of failure is “Plating”. This occurs when there is a DC current in the water (usually bleed off from some type of equipment on the same circuit). If you notice that one sensor tip is larger than the other, you are seeing plating. Electrical current is removing material from one tip and depositing it on the other. This renders the sensor unbalanced and inaccurate.

Another possible cause is over-tightening of the sensor in the tee. Over-tightening will cause the sensor body to go out of round, allowing a leak to occur. The sensor has an NPT thread which should be wrapped with pipe tape before installation. “Tight” is finger tight plus ½ – ¾ turns. The sensor should be tightened with a wrench, not by sticking a screwdriver between the standoffs and torqueing the sensor.

The last probable cause of failure is simple age. We warranty our boiler sensors for 1 year from the date of shipping during normal use. Improper plumbing causing steam flash damage, chemical damage, and plating caused by current in the water are excluded from the warranty.  Physical damage such as a broken standoff from improper tightening of the sensor are also excluded.

A properly placed sensor, in a properly piped system, should last a good number of years. We have customers that have had the same sensor in place for over 10 years with no problems. They have implemented a monthly cleaning protocol that assures the sensor is kept in good condition.

As always, please call our technical support department with any questions or problems. 800-228-0839.