Boards Switches Sensors

Select Your Harman Pellet Model

Pellethead offers a wide range of Harman control boards for all of your needs, ranging from the 4-output circuit board that comes with 3 knobs and 3 shafts, to older manual ignition control boards. The control board of the stove, also known as motherboard, or mainboard controls critical functions of the stove. The sensors that a Harman control board uses is an ESP (exhaust temperature probe) and a RSP (room sensing probe). The ESP comes in either a red or black, (replaces older white wire) which is controlled by the settings on your control board. Other safety switches of the Harman pellet stove include a vacuum pressure differential switch that ensures the unit has proper draft.

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Harman pellet stoves use a number of different control boards based on the model and year of manufacturer. The most common Harman control board is their ‘Platinum Board’ which is used on most automatic Harman stoves. This video will go through the operating modes and basic overview of the features and functions of this style Harman control board.

The vacuum or differential switch is a key component in making your Harman stove safe to operate.  The differential switch is also known as a vacuum switch.  The switch will measure the air pressure difference from inside the firebox.  Once this switch is activated it allows the feed system to kick in.   If you have an air leak from a door gasket, hopper lid, or a vent blockage this would cause the switch to open and prevent the stove from feeding.  Please watch the video below for more information.  If your board has a 2 blink error this is usually due to a failed vacuum switch or an air issue not allowing the vacuum switch to properly lock in.

The Harman ESP or Exhaust Sensing Probe is an advanced system used by Harman to measure how much heat the stove is producing out the exhaust to deliver precision heating control.  It will constantly monitor and adjust heat output to maintain set temperatures +/- 1 degree.  Some common symptoms of a bad ESP probe is your stove not shutting completely down after cooling, your distribution / room fan not turning on or off, or improper heat output based on your control board selections.  Your ESP may need to be replaced if your status light has a repeated 3 blink error. The below video illustrates how to clean and remove your ESP.

Another common sensor that Harman pellet stoves use is an RSP or room sensing probe.  If your stove operates on stove temp, but not on room temp, the likely culprit is a bad RSP.  These are inexpensive and easy to replace.  If you have a 4 blink error this is more than likely associated with a bad or unconnected RSP.