Short answer: A seal that no longer touches the sill can fail in two visibly different ways: the exposed contact material looks damaged or missing, or the drop assembly does not move to the same position during an ordinary door-close cycle. These observations suggest different questions for a technician; they are not a remote diagnosis and do not identify a compatible replacement part. NGP's own installation sheets distinguish the case, plunger, spring/drop-bar assembly and separate rubber or brush seals. [N07, N08]
First establish the right mechanism
A fixed sweep or door shoe is not the same as an automatic bottom. In the NGP 680 and 220/222/229SS instructions, the bottom has a hinged-side plunger (adjusting nut) associated with a moving drop bar; NGP describes the item as handed and says it is positioned for the specified push-side installation. A door-bottom silhouette alone cannot tell you whether the installed unit is 680, 222 or another series. [N07, N08]
Compare the installed label and the documented family. The 680 cut sheet depicts a black nylon-brush contact element with an EPDM insert; 222N depicts the elastomer-style bottom. Only use the picture as an identification cross-check for those named products, not a parts-interchange map. [N03, N04]
Observation table — no disassembly needed
| What you can observe | What it means—and does not mean | Useful next question |
|---|---|---|
| Brush is missing/uneven while the bar appears to descend on ordinary closing | Contact-material wear is a candidate, but the brush and its carrier identity remain unknown | Is the exact series serviced with a separate original brush insert? [N04, N08] |
| Bar seems stationary while the door closes normally | This suggests the actuation path needs professional inspection; it does not prove a failed spring or plunger | Is the specified handing/actuator geometry present? [N07, N08] |
| Seal touches at one end but leaves a gap at the other | Could reflect door, sill or installation geometry rather than a material defect | Can the door/sill clearance be checked without alteration? |
| Closing/latching force changed after a prior adjustment | Stop further adjustment and document the changed symptom; NGP warns that over-adjustment can damage internal components | Can a qualified technician restore the manufacturer-specified operation? [N07, N08] |
What to document for a dealer or door technician
Take four photographs: the full bottom in its open / at-rest position; the product/length/finish markings; a clear end-on view of the contact material if accessible without removing covers; and the sill contact location with the door closed only during normal safe operation. Make a short written log of what changed, which side the plunger is on if visible, whether the opening is a single door or pair, and whether a floor covering was altered recently. If the contact bar is concealed, write not observable. No crawling below a moving or powered door, disassembly, forceful actuation, or improvised adjustment is needed for this record.
NGP's 680 instructions document that two seals are fitted into the drop bar, and warn against over-adjusting the plunger because it can cause internal component failure. This shows why replacing visible bristles would not automatically solve an actuation problem. But the published sheets do not establish that an arbitrary historic assembly has a separately orderable service insert. [N08]
What we do not know from a symptom alone
We cannot determine exact spring condition, carrier wear, correct brush length, model revision, net length, compatible insert, or the applicability of a fire/smoke listing. An opening that must reliably close and latch—especially a rated or egress door—needs professional review, not home diagnosis. If the manufacturer cannot match the component from the model and photographs, request its replacement-unit or official service recommendation; do not make a substitute fit claim. For generic, unrelated mechanisms see the site's automatic door-bottom profile; this guide focuses on the NGP model-family symptom distinction.
Sources / scope
- [N07] NGP,
220, 222, 229SS Surface Mounted Automatic Door Bottom, instructions marked8.25, p.1-2, Hand the ADB; Install Door Seals; caution; US: https://www.ngp.com/plugins/NGPAdmin/data/products/220-222-229SS-Seal-Gasketing-Install-25.08.pdf - [N08] NGP,
680 Heavy Duty Automatic Door Bottom, instructions marked9.25, p.1-2, component labels, Door Seals and plunger warning; US: https://www.ngp.com/plugins/NGPAdmin/data/products/680-Seal-Gasketing-Install-25.09.pdf - [N03] NGP, 222N cut sheet
NGP-GKT-222N-PCS-0626-A, p.1, exact model/section; US: https://www.ngp.com/plugins/NGPAdmin/data/products/222N_cutsheet.pdf - [N04] NGP, 680 cut sheet
NGP-GKT-680-PCS-0626-A, p.1, exact model/section; US: https://www.ngp.com/plugins/NGPAdmin/data/products/680_cutsheet.pdf
Troubleshooting here means observation and evidence collection, not repair instruction or a safety-critical field diagnosis.