(NGC) Hot Air

[trippah]

A neighbor called and asked me "Which way does the air filter in the hot air furnace system go?  Well I answered, there is a red arrow above which is are the words AIR FLOW  on the spine- just line the arrow up with the direction the air goes..  I went to look at mine and yup, that is what is happening I tell him, arrow pointing towards the duct system.  A few minutes later he calls back...NO NO NO, arrow always should point towards the blower moter another neighbor who has worked on home heating systems has informed him.  A quick search on the web seems to have both as correct. Wiki says towards ducts but another video from Hiel(? ) says arrow  always towards the blower motor.  Hmmm.  Any help would be appreciated.  meanwhile I'll go back to trying to loosen a 30 year rusted in screw in the old basement wash sink.

[John A]

That’s a head scratcher alright. On Mom’s furnace it has an arrow with the words airflow which makes me think maybe furnaces could be either an air pusher or a puller, depending on which side of the blower the filter is on. Ours has a fancy dust zapper and only goes in one way.

[AJ Huff]

Pretty sure I've always put in arrow toward the blower. I've also never believed that there is anything unique about the construction of the air filter that makes it even matter.

-AJ

[guzzisteve]

Air filter has arrow on it. It goes in furnace cold air return TO the blower usually. Arrow goes in direction of cold air returning to furnace. Never seen a filter on the warm air side.

[Motormike]

Exactly.  Cold air return, arrow points toward air handler, blower.  If you've ever seen one installed backward for any length of time you know what can happen.  Most filters only have a mesh, screen or other support on one side.  This reinforced side goes towards the blower.  It prevents the airflow from tearing the filter element apart and into the duct work/blower fan.  I once purchase a home where the filter had been installed incorrectly, then never changed for who knows how long.  When I pulled the cover off, the filter had a large hole in it and most of the filter media was packed in around the blower squirrel cage.  Wasn't doing much filtering at that point.

[80CX100]

Air filter has arrow on it. It goes in furnace cold air return TO the blower usually. Arrow goes in direction of cold air returning to furnace. Never seen a filter on the warm air side.

     ^^^^^^^This^^^^^^

     As to the other comment re the construction of the filter and if it makes a difference, absolutely.

     Depending on the quality/price, every filter I've ever seen will have some type of reinforcement (wire mesh/cardboard weave etc) on the side of the furnace/blower to keep the filter in one piece and prevent it from falling apart and getting sucked into the furnace.

     fwiw

[Iron Cross Junction]

I am seriously disappointed, as I got excited when I saw the topic title and thought it was a new subthread for lawyers.   

And, rats, too, I even knew the answer on something (semi)technical but came here too late to look smart. 

Bill