Zero International 323AA Sill ...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$104.54
Zero 323AA Light-Duty Mortised Automatic Door Bottom

Zero International 323AA Sill Protection Automatic Door Bottom with Neoprene Insert - Mortised - Clear Anodized Aluminum

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Model: 323AA 18

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

$104.54
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Zero 323AA Light-Duty Mortised Automatic Door Bottom

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.

  • Sill Protection Automatic Door Bottom
  • Mount: Mortised
  • Regular Duty
  • Insert: Neoprene
  • Finish: Clear Anodized Aluminum
  • Specify handing
  • Maximum effective drop: 1"
  • Fire Rated
  • Rated for 5 million cycles
  • ZERO’s patented automatic door bottom technology ensures a tight seal against the floor or saddle. As the door is closed, an adjustable "plunger" is compressed against the door frame, activating a concealed flat spring mechanism. This mechanism drops the seal smoothly from the housing in a scissor-like motion as illustrated below. The door seal compresses tightly even on uneven surfaces and retracts automatically when the door is opened.
  • All ZERO automatic door bottoms function the same way. The concealed spring mechanism causes the insert seal to activate on the hinge side first. It prevents the seal from dragging along the floor or threshold while the door is being closed to avoid door hang-up or closing delay.
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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
Department:
Door Hardware

Zero International 323AA 18 – Frequently Asked Questions

1) Do I have to specify handing when ordering a Zero 323AA automatic door bottom?
Yes, handing is a required choice on the 323AA. It's stocked as left hand and right hand, and the reason is mechanical: the concealed spring mechanism drops the seal on the hinge side first so the insert doesn't drag across the floor or threshold as the door swings shut. Order the hand backwards and the seal activates on the wrong end of the door. Stand outside the door, on the side it swings away from you: hinges on the right is right hand.
2) What lengths does the Zero 323AA door bottom come in, and can I cut it down to fit my door?
Two lengths are stocked, 18 inches and 42 inches. A 42 inch unit covers a standard 3'0" door once you allow for the mortise pocket; the 18 inch is for narrow leaves and small openings. Because the 323AA is an automatic bottom with a spring mechanism and a plunger at the hinge end inside the housing, it is not a sweep you trim freely to length like a solid door shoe. Pick the length that suits the leaf rather than planning to cut it short.
3) How big a gap under the door will the Zero 323AA seal?
Maximum effective drop is 1 inch. That's the working travel from the housing down to the floor or saddle, so measure your worst undercut across the full swing, not just at the latch. If the gap runs beyond an inch anywhere along the opening, the 323AA won't close it and you need a threshold or saddle to bring the floor up first. Within that range the neoprene insert compresses to the surface even where the floor is uneven, and retracts as soon as the door opens.
4) Can I use the Zero 323AA on a fire rated door?
Fire rated, and rated to UL10C. That's the positive pressure fire test standard, which is what most current commercial fire door assemblies are inspected against. The 323AA also blocks air, sound, smoke and flame passage at the sill, which is the gap a fire door leaves open once everything else is sealed.
5) What's the difference between a mortised automatic door bottom and a surface mounted one?
The 323AA is mortised, meaning the housing sits in a routed pocket in the bottom rail of the door so nothing shows on the face. That takes a door with enough bottom rail to take the cut, and it's a job better done on a door that's off the hinges or on new work. A surface applied automatic bottom screws to the face of the door instead, needs no routing, and is the retrofit choice when you can't or won't machine an existing leaf. Same sealing action either way, different prep.
6) Will an automatic door bottom hold up on a high traffic entrance?
The 323AA is rated for 5 million cycles and is a commercial spec part, not a residential sweep. It's built as a regular duty unit, so it suits offices, corridors, classrooms and multi-family entries. For an exterior door taking abuse or grit, a heavy duty automatic bottom is the better call. The housing and body are aluminum with a clear anodized finish, so it won't rust out at the sill.
7) Does an automatic door bottom drag on the floor every time the door closes?
No, and that's the point of the mechanism. On the 323AA the seal stays retracted in the housing while the door swings. A plunger at the hinge end hits the frame as the door reaches closed, which trips a concealed flat spring and drops the seal in a scissor motion, hinge side first. It lifts again the moment the door opens. That's why it doesn't scuff finished flooring or hang up on a threshold the way a fixed sweep does. The plunger is adjustable, so you can tune when in the swing the seal drops.
8) Is a Zero automatic door bottom enough for sound control, or do I need perimeter seals too?
The sill is only one of four edges. The 323AA seals the gap under the door against air, sound, smoke and flame, which is usually the largest leak on an opening, but the head and jambs still pass sound unless you gasket them. For an acoustic job, plan on the automatic bottom plus perimeter gasketing on the frame, and on a fire door the whole set has to be listed hardware.
9) Why is neoprene the insert on this Zero door bottom, and where does that matter?
Neoprene is the seal material that actually contacts the floor on the 323AA. It stays flexible, takes compression against uneven concrete or a metal saddle without taking a set, and it's the insert Zero pairs with their fire rated door bottoms. It's the right choice at an interior fire door or a corridor where the seal is going to be squashed against the sill several thousand times a week.
10) Will a clear anodized aluminum door bottom match the other hardware in my building?
Clear anodized aluminum reads as a satin silver and lines up with the aluminum storefront, brushed chrome and satin stainless that most commercial openings already carry. On a mortised unit like the 323AA very little of it is visible anyway, since the housing sits inside the bottom rail and only the face edge shows. For a fleet of doors it's the safe standardizing finish.
How fast can I get the Zero International 323AA 18 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 323AA 18 come with a warranty?
Absolutely. The Zero International 323AA 18 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 323AA 18?
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 323AA 18 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.
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