HVAC Filter Question

8 years ago

We recently had a pro HVAC tech out to the house to do a repair. We have a zoned system with two units. While looking at the system, he noted that we had both 1" filters at the returns, and 4" filters at the plenums. He said that the 1" filters at the returns were unnecessary and could be causing too much restriction. What I'm concerned about is that this system was built with the house, so I'm guessing that the installers knew what they were doing. On the other hand, air flow without the 1" filters greatly increases. It's not that the 1" filters are dirty. I am very diligent about regularly replacing the 1" filters every 60 days and 4" filters every 6 months.

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Comments (4)

tigerdunes
8 years ago
You don't need the 1" filters...

IMO
kevinande
8 years ago
I agree it just restricts air flow.
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Austin Air Companie
8 years ago
Double filtration can cause problems, restricted air flow is one of them.

You have a few choices with how your system was installed. The 4 inch filter is the better filter. However, if you remove the 1 inch filter eventually that return from the inlet of the filter grill to the furnace where the 4 inch filter sits is going to get filthy over time.

This where all those before and after duct cleaning pics come from.

You have a few choices. Pull the 1 inch filter out and keep the 4 inch in place accept the fact that the return before the 4 inch filter will get dirty.

OR buy a cheap 1 inch see thru filter to use as a pre-filter and leave the 4 inch filter in place. Replace the cheap filter every month and periodically check the 4 inch filter.

OR the best of the best (depending on how your 1 inch filter grill is attached) You'll have to check to see if this could work for you. Remove the 4 inch filter at the furnace and install a 4 inch lip filter at the 1 inch filter return spot. It's more or less a 4 inch filter that can fit a 1 inch filter slot, depending how the filter grill was attached to the system. This way the whole duct system is filtered and dust build up will be minimal.

Home builders and HVAC installers via a GC make all kinds of mistakes nothing along that line is without error.
Bret Maxwell thanked Austin Air Companie
sktn77a
8 years ago
"buy a cheap 1 inch see thru filter to use as a pre-filter and leave the 4 inch filter in place. Replace the cheap filter every month and periodically check the 4 inch filter."

This is probably a workable solution, just be sure to use the cheap, fiberglass, see through filter. Ideally you would get a manometer reading to make sure the return airflow isn't too restricted. It certainly prolongs the 4" filter life for up to 1 year, depending on how dust-free your house is.