On Wednesday, September 30, 2015 at 2:40:36 PM UTC-4, trader_4 wrote:
On Wednesday, September 30, 2015 at 2:15:43 PM UTC-4, Bill Gill wrote:
Everybody says to inspect your furnace filters, but they don't say what
to look for. On the TV news they always say it, then show a filter that
is completely clogged. Obviously they should be replaced before that.
So what should I look for to decide if I need to replace them. I have
been replacing them every 3 months, but when I do I can barely tell
the difference between the old ones and the new ones.

Bill

If they are conventional filters, you can see dirt, they look
darker than a new one. Mine can easily go more than a year.
It depends how dusty your environment is, if you have pets, etc.
If you can barely tell the difference, you're probably changing
them too often. The typical 1" thick fiberglass type is almost
worthless. It will hopefully stop some stuff, but to do any
kind of reasonable trapping, you need one of the 4" thick ones
or an electrostatic.

I don't know if 4" filter would fit on my furnace. At a minimum, some tin
snips would be required.

I have something very similar to this, where the filter slips into a 1" slot
in that space just above the left hand edge of the red & white label.

http://strandlund.com/wp-content/uploads/2014/02/62.jpg

The old furnace had a huge blower on the right hand side of the unit so
that is where the cold air returns are. When the new furnace was installed,
the cold air returns were just extended down to the floor and branched over
to the furnace, just like in that picture. It would take some duct-work work
to get a bigger filter in there someplace.

I use a 3 layered, reusable, washable filter that I blow out with a leaf blower about once a month. I blast it with the blower in the opposite
direction of the air-flow arrow and watch the dust fly. I also take it
apart and wash the foam sheets at least once a year.