Zero 321AA Light-Duty Surface ...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$88.84
Zero 321AA Light-Duty Surface Mounted Automatic Door Bottom

Zero 321AA Light-Duty Surface Mounted Automatic Door Bottom

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Model: 321AA 36

In Stock (leaves warehouse same day if ordered before 3pm ET)

$88.84
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The patented automatic door bottom technology from Zero ensures an efficient seal against the floor or saddle. As the door is closed, the adjustable plunger is compressed against the door frame, activating a concealed flat spring mechanism. Zero door bottoms are designed to block penetration by air, sound, smoke, and flames.

  • AA = Anodized aluminum
  • Surface-mounted. Supplied with two handing holes that allow changing handing without changing mounting orientation.
  • Fire-rated UL10C/UL10B up to 90 minutes
  • ANSI/BHMA: R3B3341

Manufacturer Resources

Product Specs

Commercial/Residential:
Commercial
Product Group:
Door Trim and Accessories
Product Subgroup:
Door Bottom Sweeps and Door Shoes
Product Type:
Door Bottom
Product Finish:
Clear Anodized
Performance Rating:
Fire Rated-UL10c
Product Substrate:
Aluminum

Zero International 321AA 36 – Frequently Asked Questions

1) What is the Zero 321AA automatic door bottom designed for?
The Zero 321AA is a light-duty surface-mounted automatic door bottom for interior applications. It automatically seals the gap between the door and floor when closed. Best suited for lightweight hollow metal or wood doors where sound control and draft sealing are needed.
2) What door widths and thicknesses does the 321AA accommodate?
Standard lengths available for most common door widths. Accommodates standard door thicknesses from 1-3/8" to 1-3/4". Verify exact door dimensions against manufacturer specifications before ordering. Can be field-cut to fit specific door widths.
3) How does the automatic operation work?
The 321AA uses a spring-loaded mechanism that responds to door position. When door closes, the drop seal automatically extends downward to contact the floor. When door opens, the seal retracts upward. No electrical power required for operation.
4) What finishes are available for the Zero 321AA?
Typically available in mill finish aluminum and dark bronze anodized finish. Some configurations may offer additional finishes. Check specific product listing for available finish options. Mill finish can be field-painted if needed to match door hardware.
5) Is this suitable for fire-rated doors?
Check manufacturer's fire rating certifications for specific applications. Light-duty automatic door bottoms may have limitations on fire-rated assemblies. Verify code compliance with local AHJ before installation on fire-rated doors.
6) What type of seal material is used?
Features flexible rubber or neoprene drop seal that compresses against floor surface. Seal material provides good sound dampening and draft resistance. Replacement seals typically available separately for maintenance.
7) How is the 321AA mounted to the door?
Surface mounts to bottom rail of door with screws through pre-drilled holes. No mortising required. Mounting template typically provided. Use appropriate fasteners for door material - wood screws for wood doors, machine screws for hollow metal.
8) What tools are needed for installation?
Basic hand tools including drill, appropriate drill bits, screwdriver, measuring tape, and level. Hacksaw or metal cutting blade if field-cutting to length is required. Installation typically takes 15-30 minutes per door.
9) How do you adjust the seal contact pressure?
Most models have adjustable spring tension or cam mechanism. Refer to manufacturer's adjustment instructions. Proper adjustment ensures seal contacts floor without binding door operation. Test door swing after adjustments.
10) What are common alternatives to the Zero 321AA?
Consider heavy-duty automatic door bottoms for high-traffic applications. Surface-mounted door sweeps offer simpler alternative without automatic operation. Check our door hardware selection for Zero brand alternatives and other manufacturers.
11) Will this work on uneven floors?
Light-duty automatic door bottoms work best on relatively flat, smooth floors. Minor irregularities can be accommodated by flexible seal material. Significant floor variations may require floor preparation or heavy-duty models with greater adjustment range.
How fast can I get the Zero International 321AA 36 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Zero International 321AA 36 come with a warranty?
Absolutely. The Zero International 321AA 36 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Zero International 321AA 36?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
Why buy the Zero International 321AA 36 from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support, and rewards on every order. Our team is always ready to help you choose the right product for your project.

Product Reviews

  • 5
    Simple Install

    Posted by Paul Shumate on Apr 23rd 2025

    Simple install to close the gap under a fire door. Works well, easy to adjust

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