Pellet Tech 101 – Vacuum Switch, Pressure Air Switch

Welcome Back to Pellet Tech 101!

Our video above will cover great oversight on vacuum switches and pressure switches, also referred to as an air switch, or draft switch. In the pellet tech world there is a distinct difference between a vacuum switch and a pressure switch. Not all replacement switches can do both, so being specific is important when ordering the correct replacement part. Most commonly used in pellet and corn stoves, the vacuum switch is detecting negative air pressure in the stove’s firebox and the pressure switch is detecting for positive pressure in the exhaust vent flue pipe. Designed as a safety switch, the vacuum switch and pressure switch are in-line with auger feed motor circuit, and will not allow the auger motor to operate if tripped or faulty. The vacuum or pressure switch is a vital component to the safety and proper operation of your appliance.

Most switches will have a positive and negative nozzle port where the vacuum switch tubing hose connects to. Most pellet and corn stove appliances are under negative pressure in the firebox and positive pressure in the exhaust vent flue pipe. It’s important that the vacuum hose is placed on the correct nozzle port; check out our video above for installation guidance. Vacuum switches will vary in size, mount, and WC rating. It’s important you are replacing your switch with an OEM or aftermarket switch that matches the specs of your existing. The vacuum or pressure switch is a normally open circuit in pellet and corn stoves and will close when proper vacuum or air pressure is met completing the electrical circuit to the auger feed motor. If at anytime during operation there are air losses or air blockages, the vacuum or pressure switch will trip and shut down power the auger feed motor.

Common reasons for a vacuum switch to trip:

• Vacuum switch tubing hose is cracked or not connected properly to the nozzle ports.
• Heavy ash build-up in the stove and venting.
• Poor or weak gasket seals – Firebox door, glass, ash pan door, hopper door (Not all units have ash pan door or hopper door gaskets).
• Weak or failing combustion blower/exhaust fan.
• Air Intake blockages or obstruction.
• Faulty vacuum switch.

General Tips :

• Closely inspect the vacuum tubing hose with a good light. Replace if there are cracks, breaks, or if it’s becoming stiff and brittle.
• Thorough cleaning of the burnpot, firebox area, ash traps, heat exchange tube area, exhaust fan manifold, and exhaust vent pipe.
• Inspect and test your gaskets. With the stove off, use a dollar bill and place half in and half out of the door, close the door and pull on the dollar bill. There should be heavy resistance. Check in multiple places around your firebox door and if applicable your ash pan door and fuel hopper lid. If there are any areas with minimal resistance, air gaps, indents, or heavy fraying, we recommend gasket replacement. Visually inspect your glass gasket; if you notice air gaps, fray, or notable signs of wear, we recommend replacing the glass gasket.
• Inspect and test your combustion blower/exhaust fan. You can use a basic voltage meter to monitor the voltage on start-up and in normal operation mode on various heat settings.

A vacuum switch can be tested and bypassed for TROUBLESHOOTING ONLY. We NEVER want to leave a safety switch bypassed in our appliance. If you have checked all the basics and are still running into issues with a tripped/tripping vacuum switch, follow along with our video below on how to further troubleshoot to determine if the switch requires replacement.

Any Further Questions or Technical Assistance Needed Please Leave us a Comment Below.

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