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HVAC School - For Techs, By Techs

Feb 19, 2019

In this short podcast episode, we discuss the common myth about cleaning flame rods/sensors/rectification devices.

Flame sensors or rectification rods are NOT the same as thermocouples or thermopiles. Thermocouples and thermopiles use two dissimilar metals to create a temperature differential. So, we do not clean thermocouples and thermopiles because the heavy abrasives in cleaners can damage and reduce the effectiveness of those devices. However, you don't have to worry about that sort of damage on a flame sensing rod; we can indeed clean those.

The flame rod sits in the flame (regardless of ignition type) and allows for a DC current to travel through the ions in the flame to ground. The flame creates a path for that current, which makes a closed circuit. Flame sensing rods are merely pieces of metal that allow current to flow when there is an active flame on a furnace.

So, you want to keep your flame rods clean to allow for conduction. You may want to avoid using sandpaper or Emory-type materials to clean the rods because sediment can build up on the flame rod. When the flame ignites, the sandy substance on the rod can turn glassy and impede conduction. However, you can use an appropriate cleaner without damaging the rod. You can also replace the rod if you happen to have one on your truck, but you don't have to replace all dirty rods.

Pool heater flame sensors can get exceptionally nasty due to the chemicals they encounter. If a piece of equipment has a flame rod that gets dirty a little too quickly, try to find the cause of the excess grime and take care of it.


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