Air Filters, Coil Cleaners and Air Treatment

Filter size, depth and rating: choosing one that fits the cabinet

Furnace filters are labeled by nominal size, such as 16x20x5, and the actual dimensions are a fraction of an inch smaller, so read the real size printed on the old filter. Depth matters as much: a 5 inch media filter belongs in a deep cabinet and cannot replace a 1 inch filter in a standard slot. Deeper filters offer more surface area and usually last longer between changes.

MERV ratings rank how well a filter captures small particles; MERV 11, as in some synthetic media filters, catches fine dust and pollen better than a basic MERV 8. Higher is not always better, because dense media restricts airflow, and a system not designed for it can run hot or lose capacity. Follow the equipment maker's guidance on the highest rating it accepts.

Coil cleaners, drain care and respirators: the supporting items

Cleaners are matched to the coil. Aqueous condenser cleaners are water-based and rinse away; acid-based ones work faster on heavy scale but can attack aluminum fins and need protective gear and thorough rinsing. Drain-pan tablets and gels are dosed by system size, and one listed for a 5 ton unit will not be right for a small split system. A drain-clearing gun clears a blocked condensate line with pressure.

Some items protect people rather than equipment. Respirators and masks carry a NIOSH approval marking, such as N95, and only approved products are rated for fine particles; a plain dust mask is not. Ultraviolet lamps for coils or ducts are used to limit growth on surfaces, but wear eye protection near the light and match the lamp to the cabinet size and power supply.

Questions about Air Filters, Coil Cleaners and Air Treatment

What MERV rating should I use at home?

Many homes use MERV 8 to 11, which captures dust, pollen and pet dander without restricting airflow much. Move higher only if the equipment maker says the system handles it. A clean MERV 8 filter changed on time often outperforms a clogged high-rated one.

How often should I change a furnace filter?

A 1 inch filter typically needs changing every one to three months, while deeper 4 to 5 inch media filters often last six months to a year. Pets, dust, construction and heavy use shorten that. Check the filter monthly and replace it when it is visibly loaded.

Can I use a thicker filter than my system had?

Only if the cabinet or rack is built for it. Forcing a thick filter into a slim slot leaves gaps that let air bypass the media. If you want deeper filtration, have a media cabinet installed, or choose a good filter of the original depth.