About this item
The Adams Rite 3889-08 is a removable steel mullion for paired doors up to 8 feet in height- used with the Adams Rite 8700 Series life-safety rim exit device and 3700 Series fire-rated rim exit device. If you searched "dl 3889", "part number 3889 specifications", "mullion lock", or "door mullion"- this is the product. The 3889-08 is the steel primer-finish version for hollow metal and wood door pairs; the -08 suffix designates door height up to 8 feet.
"DL 3889" and "Part Number 3889 Specifications": What You Are Looking For
If you searched "dl 3889"- the DL prefix is a distributor catalog lookup format used in commercial hardware purchasing systems where "DL" precedes the manufacturer part number in order forms and RFQ documents. DL 3889 and part number 3889 both reference the Adams Rite 3889 steel removable mullion series. The 3889-08 is the 8-foot height variant in that series.
What a Door Mullion Is and Why This One Exists
If you searched "door mullion" or "mullion lock"- a mullion in the context of paired exit device doors is a vertical post that stands in the center of a double-door opening, dividing the pair into two independently operating leaves. On paired doors with rim exit devices, the problem is mechanical: a rim exit device needs a fixed vertical surface- a strike- to latch against when the door closes. On a single door, that surface is the door frame. On a pair of doors, neither leaf has a fixed vertical frame at the center- each leaf closes against the other leaf.
The traditional solution on paired doors is to use concealed vertical rod (CVR) or surface vertical rod (SVR) exit devices, which latch at the floor and head of the door frame rather than at the center meeting edge. But vertical rod devices have drawbacks: they require top and bottom rod cutouts in the door, they cannot be used on some fire-rated door assemblies, and they create more complex maintenance and alignment issues over time.
The 3889 removable mullion solves this by providing a temporary fixed post at the center of the paired opening. The inactive leaf latches to the mullion. The active leaf latches to the inactive leaf. The rim exit devices on each leaf can now operate exactly as they would on a single-door opening- latching to a fixed vertical surface provided by the mullion. The mullion is removable- it can be taken out when the full paired opening width is needed for moving large items or for emergency vehicle access- then reinstalled.
3889-08 Model Decoded
3889- The steel removable mullion series for the Adams Rite 8700 and 3700 Series rim exit devices. Steel construction, primer finish only.
08- Door height designation. The -08 specifies this mullion is cut for doors up to 8 feet (96 inches) in height. Taller openings require a different length specification- confirm door height before ordering. An undersized mullion will not span the full door height and will not properly engage the strike at both top and bottom contact points.
3889 Steel Mullion vs 3890 Aluminum Mullion: Critical Distinction
The Adams Rite 3889 and 3890 are both removable mullions but are not interchangeable:
3889 (this listing): Steel construction, primer-only finish. For use with 8700 and 3700 Series rim exit devices specifically. Used on fire-rated applications (3700 Series) or non-rated applications on hollow metal or wood doors. Available in primer only- it must be painted to match the door finish on site. Primer-only is standard practice for steel mullions in commercial hollow metal door applications where the installer applies the final color coat.
3890: Aluminum construction, anodized finish (313 dark bronze or 628 clear anodized). For use with the 8800 Series narrow stile rim exit devices on aluminum glass storefront doors. Available in 8-foot and 10-foot heights.
If your exit devices are the 8700 or 3700 Series on hollow metal or wood doors- order the 3889. If your exit devices are the 8800 Series on aluminum narrow stile doors- order the 3890. Using the wrong mullion series means the strike engagement geometry will not align with your exit devices.
Why Rim Devices with a Mullion Outperform CVR on Paired Doors
Adams Rite's own catalog states this directly and no competitor product page repeats it: the 3889 removable mullion provides higher security and better traffic flow than paired doors with vertical rod exit devices.
Higher security: Rim devices with the Adams Rite Starwheel interlocking bolt mechanism provide deadlocking engagement when the door closes. When the door closes, the interlocking noseguard and Starwheel bolt close around the strike, and the deadlocking slide springs over, locking the Starwheel bolt to the strike. This over-center deadlocking action prevents the bolt from being pushed back by spreading the door frame. CVR devices that latch at floor and head do not provide the same center-of-door deadlocking engagement.
Better traffic flow: On a pair of doors, the inactive leaf can be held fully open by the mullion configuration, or both leaves can open simultaneously for large-object movement. CVR exit devices on paired doors often require sequential operation- one leaf must be opened before the other because the rods require specific stroke sequencing.
8700 vs 3700 Series: Which Devices Use This Mullion
8700 Series: Life-safety rim exit device for hollow metal and wood doors. UL 305 panic hardware, ANSI/BHMA A156.3 Grade 1. For non-fire-rated applications where panic hardware is required.
3700 Series: Fire-rated rim exit device for hollow metal and wood doors. UL 10C fire-rated up to 3 hours, CAN/ULC S104, NFPA 252 conformant. For fire-rated paired door assemblies where both life-safety egress and fire rating are required. The 3889-08 is confirmed compatible with both 3700 (fire-rated) and 8700 (non-rated) series- the mullion itself carries the steel construction that satisfies fire-rated paired door assembly requirements.
Specifications
Model: Adams Rite 3889-08
Type: Removable steel mullion
Compatible Devices: 8700 Series life-safety rim exit device, 3700 Series fire-rated rim exit device
Door Height: Up to 8 feet (96 inches)
Material: Steel
Finish: Primer only- field paint to match door finish
Aluminum Mullion Alternative: 3890 (for 8800 Series narrow stile on aluminum doors)
Door Types: Hollow metal, wood
Applications: Paired door openings requiring rim exit devices without door narrowing; fire-rated and non-rated assemblies
Fire Rating: Compatible with fire-rated assemblies (3700 Series)
American Locksets has stocked Adams Rite exit device hardware since 2001.
Trusted Since 2001
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