Repair or replace · Hoods
Loud Hood on a 1990s Duct: New Hood or New Duct?
Short answer
A Viking hood that roars on every speed may be fighting its duct rather than failing. Viking Repair Sammamish checks the duct size, the elbows and the damper against what Viking asks for that ventilator before touching the blower. If the duct is wrong, a new hood on it stays loud. Call (425) 610-8986.
- 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
On the bench
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We measure the duct diameter where it leaves the hood
It tells us whether it matches the round size Viking pairs with that ventilator
So we know if the duct is undersized before we touch the blower.
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We measure the elbows and the length of run we can see or trace
It tells us how much straight run the fan is really pushing against
So we hold it up to the limits in Viking's installation guide.
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We measure the sound on each speed with the filters out
It tells us whether the noise follows the air or stays with the motor
So we separate a worn bearing from a restriction.
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We measure the damper flap's travel with the power off
It tells us whether it swings fully open or chatters half shut
So we free it before we blame the duct.
Resistance is what you hear
Viking rates its hood ventilators at 0.1 inch of static pressure and notes that, measured without it, the airflow figures would be greatly overstated. Resistance in the duct is the gap between the rated number and what reaches the roof cap. The installation guide counts each 90-degree elbow as five to ten feet of straight run, and it forbids flexible duct outright because it creates back pressure and turbulence. A blower pushing into that sounds strained.
What Viking asks of the duct
For its professional wall hoods, Viking pairs a 7-inch round duct with the 300 and 600 CFM interior ventilators and a 10-inch round duct with the 1,200 CFM interior and the exterior ventilators. Over a rangetop with a gas char-grill, a 1,200 CFM ventilator is held to a 50-foot run; for longer runs the guide recommends the 1,500 CFM unit, up to 75 feet. The duct must be metal. A duct laid for an earlier hood was sized for that hood.
Moving the motor or damping it
Viking’s 36-inch 5 Series chimney wall hood, the VCWH53648, lists interior, in-line and exterior ventilator kits, and the last two put the motor away from the cooking area. Viking also lists a duct silencer and a vibration silencer among its optional accessories. Changing the ventilator type or the duct is installer work. We tell you what the duct measured and what the ventilator is doing, so the money goes to the part that makes the noise.
Repair or replace: the signs
Repair the hood when
- The noise comes from a sticking damper or a loose ventilator mounting
- The duct is the right size and the ventilator's bearings are wearing
- Grease on the blower wheel has thrown it out of balance
Change something bigger when
- The duct is smaller than Viking specifies for the ventilator now fitted — a new duct, laid by the installer
- A length of flexible duct sits somewhere between the hood and the cap
- The hood was upgraded to more airflow than the old run was built to carry
Verdict When the duct is right, repair the ventilator. When the duct is wrong, a new hood on it stays loud: the fix is the duct, and laying it is the installer's job.
What it costs here
- Diagnosis visit $89
- Blower motor or ventilator quoted after the diagnosis
- Sticking damper at the hood quoted after the diagnosis
$89 buys the visit and the full diagnosis. Go ahead with the repair and that $89 is taken off its price. The replacement side is not priced on this page: it depends on the unit you choose and who installs it.
Asked about this
Will a more powerful Viking hood fix a loud, weak one?
Not on a duct that is already too small. Viking rates its ventilators at 0.1 inch of static pressure, and a stronger fan on a restrictive run meets the same resistance. Viking Repair Sammamish measures the duct first and tells you which change actually helps, (425) 610-8986.
