Different Types of Boiler Air Pressure Switches

Different Types of Boiler Air Pressure Switches


Boilers burn fuel, and to do that, they need air. Not just for combustion purposes, but also for the crucial ventilation processes that keep boilers operating safely. These switches come in a variety of styles and names. “Air Pressure switch”, “Combustion air switch”, “Air proving switch”, “Differential pressure switch” are just some of the monikers used to describe these switches and their functions. They all provide different functions from proving air movement during purge cycles to measuring the draft on the exhaust. 


Combustion air switches on forced-draft burners provide a safety function by making sure there is airflow through the burner and furnace. When a boiler kicks on, it goes through a purge cycle that ensures a certain number of air changes occur throughout the boiler. This is to confirm that there is no residual unburned fuel collecting in the combustion chamber. As long as the pressure switch is made for the set amount of time required for that individual boiler, it will be able to communicate to the flame safeguard that it is safe to go to the next step and light a flame in the combustion chamber.


Once the boiler is past the purge cycle and is up and running, the combustion air switches make sure that there is enough incoming air to support proper combustion. If the pressure drops below the switch’s set pressure range, it will shut off the burner. This helps protect the boiler from a variety of issues and failures having to do with thermal stress, and with mechanical failures from the forced-draft fan.


There are a wide variety of air pressure switches out there because there are a wide variety of pressures to measure inside a boiler. Some switches just sense a certain set point, others measure a differential pressure from two different points. Others may even sense a negative pressure like those found in boiler vents and exhaust systems.  

No matter what kind of air pressure switch you need, WARE has a complete inventory ready to go. We also have the expertise to install them correctly. If there’s anything we can do to help your boiler run smoothly and safely, we’re here to help. Just contact us at your convenience. 

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