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furnace filter mystery

I just had a HVAC technician to the house to perform a yearly tuneup on my furnace and A/C. He confirmed a suspicion I had for some time now. The return air filter doesn't fully span the duct. There is a piece of strapping screwed into the inside of the duct that was obviously put there to act as a stop at the far end of the filter track. Once I slide the filter in and it hits the stop, there is about a two inch gap on the far side of the duct that isn't blocking any air. The tech said the filter is doing next to nothing in this situation and the motor is filthy as a result (to say nothing of the potential for terrible indoor air quality). Can anyone think of why this strap stop may have been put in? This is the third tech to see the unit in the past three years and no one has said anything until now. Is this guy off base? He recommends reworking the ductwork so the filter fills all gaps. Thanks for your thoughts.

A. Spruce
Re: furnace filter mystery

Well, noticed or not, if the air can bypass the filter, then the filter can't do it's job. Rather than reworking the duct, which will likely be expensive, why not add a filter grill to the return air inlet(s )?

Re: furnace filter mystery

Or move the stop and get a bigger filter.

Re: furnace filter mystery

well if you don't want to get correct filter then just replace whole furnace

then you'll have a clean motor too


Re: furnace filter mystery

Is it a stop or is the filter supposed to go on side of it to keep it from being pulled into the Blower?

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