4" Smoke Chimney Cap

Lukjan Non-Adjustable Rain Cap — Series 47, 4″ Ø, 6-1/2″ Length × 7-1/2″ Width

Fixed (non-adjustable) rain hood / vent cap designed for mounting on 4-inch round duct or flue terminations. Series 47 is a Lukjan line of rain / vent caps that provide weather protection while allowing airflow. The cap’s dimensional footprint (6½″ depth and 7½″ width) ensures adequate overhang and protection from precipitation.

• Series / model: Series 47 non-adjustable rain cap (Lukjan)
• Nominal duct connection: 4 inch diameter (round duct)
• Overall length (depth / projection): 6-1/2 inches (6.5″)
• Overall width (across hood brim): 7-1/2 inches (7.5″)
• Material: Galvanized steel (standard sheet metal construction for rain caps)
• Finish: Galvanized coating (corrosion protection) or optionally painted / coated per installer preference
• Gauge (thickness): Likely 28 or 29 gauge (common for ventilation rain caps; subject to confirmation)
• Weight (approx): ~0.25 lb (estimated for small rain cap) — actual depends on gauge
• Mounting / connection:
  • Slip or drive-in fit over 4″ round duct end; edges may be crimped or flanged for screw fastening into duct or flashing
  • Use sheet-metal screws (e.g. #8 or #10) spaced at flanges or lugs at the cap’s base
  • Seal joints with high quality exterior sealant or flashing as needed to prevent water ingress
• Function / purpose:
  • Provides overhead protection (hood) to prevent rain, snow, and debris ingress into vent duct while allowing exhaust / intake airflow.
  • Non-adjustable design means no movable parts — simpler, more durable in many installations.
  • Overhang and brim width ensure coverage even under wind-driven rain conditions.
• Design & performance considerations:
  • Brim width (7.5″) provides sufficient radial overhang relative to the 4″ duct to limit splashback and water entry.
  • Projection (6.5″) allows vertical clearance and helps shield the duct opening in heavy rain.
  • Interior clearance: ensure the internal hood clearance does not obstruct airflow or gather debris.
  • Wind loading: cap should resist uplift or deformation due to wind, so gauge and fastening must be adequate.
• Compatibility & application notes:
  • Intended for use on vents, flues, or duct terminations where a 4″ round opening requires weather protection.
  • Not suitable for adjustable up/down dampers, as it is nonadjustable (fixed hood height).
  • Ideal for roof or sidewall terminations; may require flashing, counter-flashing, or enclosure support per local codes.
  • In corrosive or coastal environments, optional upgrades to stainless steel or painted finish may be recommended.
• Installation recommendations:
  • Ensure the duct end is cut square and free of burrs before installing the cap.
  • Use corrosion-resistant screws and sealant when fastening to avoid leaks or corrosion over time.
  • Provide accessible inspection / cleaning, as caps may collect leaves, nests, or debris at the opening.
  • Verify that the installed cap does not violate required clearances to walls, eaves, or other obstructions per building/vent code.
• Maintenance:
  • Periodically inspect for corrosion, deformation, or clogging from debris.
  • Clean inside hood if obstruction occurs (e.g. leaves, nests). Ensure fasteners remain tight.
  • Retouch finish or apply rust-inhibitive coating as needed to maintain long service life.