Summary
This article explains how to determine the correct AC or furnace filter size when the existing filter is missing. A short video at the top demonstrates where to look and how to measure properly.
When to use this
Use this guide if you are:
Unable to find an existing AC or furnace filter
Unsure what filter size your system requires
Looking at an intake grill and unsure if it holds a filter
Replacing a filter for the first time
Video: Determining AC and Furnace Filter Size
This video demonstrates how to locate the intake grill, open it safely, and measure for the correct filter size.
Overview
AC and furnace filters are commonly located behind an intake grill or inside a filter housing. If a filter is missing, measurements must be taken to determine the correct replacement size.
Using the correct filter size is important for proper airflow and system performance.
Common Questions Covered in the Video
What Is an Intake Grill?
An intake grill is the opening where air is drawn into the HVAC system. It is commonly located:
On a wall
On a ceiling
Near the air handler or furnace
Determining if the Intake Grill Holds a Filter
The video explains how to:
Identify whether the grill is designed to hold a filter
Recognize filter tracks or slots behind the grill
Opening the Intake Grill
The video demonstrates how to:
Open or remove the grill
Identify hinges, latches, or fasteners
Avoid forcing the grill open
Measuring for the Correct Filter Size
The video explains where and how to measure:
Width and height of the filter opening
Depth of the filter slot
Measurements should be taken from the opening itself, not the grill cover.
Tools Needed
Basic tools such as a tape measure are typically sufficient.
Filter Thickness
The video explains that filter thickness is not always one inch. Some systems require thicker filters depending on the design.
Screws and Caulking on the Grill
If screws or caulking are present, the video explains:
The grill may not be intended for tenant access
Maintenance assistance may be required
Troubleshooting
No visible filter slot → Filter may be located elsewhere in the system
Grill does not open easily → Do not force it
Unsure of measurements → Contact maintenance for confirmation
FAQs
Q: Is the filter thickness always one inch?
A: No. Filter thickness varies by system.
Q: Can I install a filter if one is missing?
A: Only if the intake or housing is designed to hold a filter.