Rubycon
Madame President
The homemade solution is more of a dirt catcher than a filter. Box fans are designed to work with a very low pressure. Non pleated media don't restrict too bad. Not all fan blades are the same - some will load heavier if there is a restriction and some will actually unload at restriction! The motors are thermally protected but remember a few things here:
Open air over cooled motors depend on a constant flow of air over them. If you take the fan apart and put the motor on a table with its shaft spinning the casing will actually get hotter over time than if it were in the fan running with a higher load! So open air over cooling diminishes with air flow. If the design loads the motor down as airflow is restricted this makes the windings hotter along with less air to cool them. So keep this in mind as you may wind up with tripping of the motor winding thermal overload. Also a filter's efficiency increases with use. As it clogs it will let smaller and smaller particles pass at the expense of higher restriction of flow.
Pleated high efficiency or HEPA filter media will not be effective with this type of application. You can use washable elements and spray them with "filter enhancer" which basically makes it sticky to attract more airborne pollutants. Keep in mind this will require more frequent attention as it turns it into a dust magnet.
Finally it's quite easy to measure the amps of a box fan as pictured. (Carefully) use a razor blade to split the conductors apart on the line cord forming an area large enough to get your clamp on (amprobe, etc.) in there. Take a reading on HIGH with no load, then lay the fan on the floor and take another reading. Compare the blocked reading with the FLA (full load amps) which should be stamped on the motor housing.
Have fun, but be safe! 🙂
Open air over cooled motors depend on a constant flow of air over them. If you take the fan apart and put the motor on a table with its shaft spinning the casing will actually get hotter over time than if it were in the fan running with a higher load! So open air over cooling diminishes with air flow. If the design loads the motor down as airflow is restricted this makes the windings hotter along with less air to cool them. So keep this in mind as you may wind up with tripping of the motor winding thermal overload. Also a filter's efficiency increases with use. As it clogs it will let smaller and smaller particles pass at the expense of higher restriction of flow.
Pleated high efficiency or HEPA filter media will not be effective with this type of application. You can use washable elements and spray them with "filter enhancer" which basically makes it sticky to attract more airborne pollutants. Keep in mind this will require more frequent attention as it turns it into a dust magnet.
Finally it's quite easy to measure the amps of a box fan as pictured. (Carefully) use a razor blade to split the conductors apart on the line cord forming an area large enough to get your clamp on (amprobe, etc.) in there. Take a reading on HIGH with no load, then lay the fan on the floor and take another reading. Compare the blocked reading with the FLA (full load amps) which should be stamped on the motor housing.
Have fun, but be safe! 🙂
