Does the air flow (and thus the air filter) for forced hot air furnace go in the same direction for heat & air

Question

I know that the arrow on the filter must face the same way as the air flow, but don't know if the air flows into furnace or out of furnace at the point where the filter is placed. Also think maybe it is different when I run the air than when I run the heat. I am getting cold...I need an answer. Thank you. Pat

Answer 1

You can test it easily enough. Turn on the system, then hold a paper napkin or something similar in the opening where the filter goes. see which way the airflow pulls the paper.

Answer 2

Two-part answer: Simple spun-fiber furnace filters pretty much only get the 'big stuff' and do not do much with small particles. They also have a relatively small surface area *because* they do not have a potential to clog as quickly. More efficient filters have many pleats (folds in the filter element) so as to give a much greater surface thereby allowing good air transfer even though they trap smaller particles. This balances the fact that more material is trapped leading to clogging. That is part of the basic design. However, when new, a high-efficiency filter presents no more air resistance than a conventional filter - the operative phrase being "when new". The more efficient (smaller-particles trapped) a filter is, the more potential it has to clog. And if you are in a dusty/particle-rich environment it will clog quickly no matter how well designed it may be otherwise. Add to this that such filters are relatively more expensive than conventional filters and you have a dilemma - get the efficiency but sustain the cost. I strongly suggest that you purchase two passive washable electrostatic filters sized correctly for your system. Change them weekly, washing each one as it comes out of the system. You get the best of both worlds - high particle filtration (including some ultra-small ionized allergens) without the potential for great clogging - and after the initial investment (about the same as 8 high-end filters), the filters are re-usable. I have linked you to one source (of a great many) that does custom sizing. However if you have a standard size they are often available at any given big-box store. MAKE SURE!! that whatever you purchase is rated to be cleaned many times. And, again buy two. One clean and ready to drop in, and one in service.

Answer 3

Most furnace filters are placed at the front of the system (where are flows in) to protect motors and fans from getting dirty. Placing a filter element at the output end could potentially be a fire hazard. There should be no difference between the filter when setting to hot or cold.

Answer 4

The air through the heating/cooling system always goes in the same direction.