specific question on bug screens

I know, this sounds silly. But I put remnants of dog flea collars in the outside of the water heater and the fridge. Have never had a problem after I started to do this.

Before, I had a water heater while up at Denali not start because of a spider web made overnight. They love the smell of LP.

I do put a screen on the furnace output so mud dobbers do not get in there.

manufacturers probably recommend against the use of screens because some people not knowing any better will make flat screens to cover the openings.

The stainless screens sold comercially for furnaces and water heaters are bowl or pan shaped and larger than the opening instead of fitting flat against the side of the trailer.

That allows for the same amount of air that would normally pass through without restricting air flow. It is when the total area of all the holes in the screen is less than the opening that causes a restriction in flow. Making the screens 3 dimensional adds more total surface area than the appliance opening.

When making your own screens the total surface area needs to be taken into account. Screen mesh has to be sized small enough to keep the spiders, wasps and daubers out but not restrict flow. Home made screens should not be smaller than the commercial made screen for the particular appliance. If you can't find the larger screen locally it can be ordered through McMaster Carr.

Stainless hardware cloth

Double post on editing

I've had the Camco screens on our furnaces, fridge, and water heater since 2008. No problems and no bugs...