I bought a house with a Bryant Furnace (310JAV04290AAJA). There is no slot for an air filter anywhere in the system, instead the previous owner duct-taped a 20x20x1 filter over the duct opening (which is just a grate over a metal box in the floor with a large duct opening that leads to the furnace). The filter gets dirty constantly (even shutting down the furnace at one point) and I'd prefer to use something more robust, like a 20x20x5 box filter, but I don't want to overload the blower if it's not meant for that thick a filter. How can I tell what kind of filter I can use with this furnace?

I have a Weil Mclain Oil furnace. It is very difficult to clean, the brush gets stuck all the time because the boiler plates are very close together and the cleaning opening on the top of the furnace is off center so you need to bend the wire brush to get to some areas of the boiler plates. It takes dozens and dozens of passes with the brush to get the soot off the boiler plates and down to bare clean metal, at the same time with almost every pass the brush gets stuck. Also due to the opening being off center there are areas of the boiler plates that are very difficult to get to so I must bend the wire brush to get into these spots. The bending has to happen several times with each pass of the brush so again with dozens of passes I am constantly bending the wire brush back and forth to clean these areas. It takes hours to clean the boiler. I have a wood burning stove and I clean the flue pipe with a wire brush. It would take a long time and dozens of passes with a wire brush to clean out all the soot and get to clean bare metal. I started using creosote remover products in the wood stove a few weeks before cleaning and now when I clean the wood stove flu it is sparkling clean with just a few passes of the brush and I am done in no time. I see they make soot remover products for oil furnaces. I was thinking that I could use these products in my furnace a few days before taking the furnace apart to clean with the wire brush and hopefully get the same results, just a few passes of the brush and clean as a whistle. Any thoughts on this idea? And since I already have creosote remover can I use this or do I need to use the soot remover product? I see they make both creosote remover and soot remover and I did not know if there was an actual difference or are they the same? I have used Rutland creosote remover and ACS creosote remover in my wood stove. Rutland also makes a soot remover powder and a stick (Kwik Stick) you put in the fire box of the boiler. Since I already have the creosote remover and if they are the same I do not see the point in buying another product just because the product name is slightly different.