Run the attic HVAC/Furance without an Air Cleaner/Purifier Filter

I have the same filter location as referenced by Steve Armstrong. There is no slot for the filter but it is just held in place over the return duct by a metal arm.

Here is the opening between the return and the blower: alt text http://serverintellect.jeffwids.com/public/20100802_762_furnace_filter.jpg

And here is the filter in place over that opening with the metal arm holding it in place: alt text http://serverintellect.jeffwids.com/public/20100802_762_furnace_filter_2.jpg

I would not have known a filter was supposed to go there if there hadn't been one there already.

First off I did not see anything in the video to make me think there was a cracked heat exchanger. The heat exchanger may be cracked but the video does not indicate so. It seems that removing the inlet pipe fixed the problem? The furnace installation instructions has vent tables showing what size pipe can be used for various lengths and amount of elbows. For instance a 90,000 btu furnace can have a maximum of 70’ of pipe and 4 elbows with 3” pipe but only 20’ of pipe and 4 elbows with 2” pipe. And this is combined for both pipes, not for each pipe. So adding the second pipe may have pushed you over the limit. This furnace comes with a restriction plate that must be installed if using only 1 vent but must be removed if using 2 vents. Was it removed? And in my experience these tables are often over generous. I have pushed the limits of the tables and have had venting problems. I had to either increase pipe size or reduce the amount of elbows or both.