furnace vent screen

[John Dirks Jr]

I saw these screens in 2" furnace vent and intake openings. They sure do look like they would obstruct flow. In the winter here, it's common to see ice forming at the exhaust termination in longer cold spells. These screens look like they would allow ice to create blockage of combustion venting. Are these pieces standard for furnace vents? Do these look problematic to you?

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[Chad Fabry]

They're blocking more than half of the opening- I guess it depends what size the furnace is and /or what the directions say. If the directions specify 2 inch pipe then yes, it's a problem.

[Jim Katen]

Find the manufacturer's instructions and see what they say. Some manufacturers require a screen. I've never seen a pre-manufactured grate like that, but it certainly might be ok.

[Jim Katen]

I just saw similar screens on yesterday afternoon's Lennox furnace. The installation instructions say that the screens are supposed to be used only on the intake pipe and only in a non-direct vent configuration; that is, when the end of the intake pipe is in the house, in an attic, or in a crawlspace. It specifically warns against using these screens when the intake is in a direct-vent configuration. The concern seems to be ice build up.