Care notes · Hoods
Checking the Duct Run and Roof Cap
- Baffle filter — grease collects on the channels and drains to the bottom
- Blower (ventilator) — the only moving part pulling the air
- Backdraft damper — opens under airflow, falls shut when the fan stops
- Metal duct — smooth and straight is best; every elbow costs draw
- Roof or wall cap — where the air finally leaves the house
- Lights and controls — the lamps and the fan and light switches on the canopy
In short
A hood pushes air only as far as its duct allows. Viking Repair Sammamish reads the run in order, damper, duct, then cap, and an owner can look at most of it without climbing: (425) 610-8986.
What the run has to be
Washington’s residential code (WAC 51-51-1503, section M1503.3) sends kitchen exhaust outdoors through a smooth, airtight duct with a backdraft damper, never ending in an attic, a crawl space or inside the building. Viking’s installation guide adds metal duct only, never flexible duct, and straight runs with gradual turns; it counts each 90-degree elbow as 5 to 10 feet of straight run.
Why we read the run before the motor
Viking rates hood airflow at 0.1 inch of static pressure, so every restriction in the run takes air off that figure. A blower spinning freely into a crushed duct or a blocked cap is not a motor fault, so we check the whole path before we price a ventilator. Above the ceiling the run is ours to read: we look for rigid metal duct, taped joints and an end at the roof rather than in the attic.
The steps
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Look up through the filter opening
Breaker off, filters out, flashlight in. On Viking's 10- and 12-inch-high wall hoods the damper sits on top of the canopy where the duct joins, so you may see only part of it. A flap bent or glued down with grease traps the air. Note it; leave it.
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Watch the outside cap from the ground
Have someone run the fan on high while you look at the cap from the yard, with binoculars if the roof is steep. Needles, moss, a nest or a flap that never lifts all show from below. Do not climb up to clear it.
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Feel for backdraft at the filter opening
With the hood off and the filters back in, hold a hand at the opening. Cold air falling in means the damper or the cap is not closing. Note it and leave it.
Call us when
- The damper is bent, stuck or glued shut with grease
- The cap outside never opens, or holds debris you cannot reach from the ground
- You know or suspect the duct stops short of the roof
Past that point it is a bench job, not a care job. Viking Repair Sammamish picks up on (425) 610-8986; the visit and diagnosis are $89, taken off the repair if you go ahead.
Asked about this
Can a Viking hood vent into the attic?
No. Viking's installation guide says ducted fans must always vent outdoors and never into walls, ceilings, attics, crawl spaces or garages, and Washington's residential code says the same for the duct's end. If yours stops in the attic, Viking Repair Sammamish will note it: (425) 610-8986.
How high should a Viking wall cap sit above the ground?
Viking's hood installation guide puts a wall exhaust at least 24 inches above the ground, and notes that local codes and location can change that. A cap lower than that, or one buried behind shrubs, is worth raising with the installer. Viking Repair Sammamish, (425) 610-8986.
