Internal, inline and external range hood blowers

There are three basic forms of range hoods blowers:

• Internal range hood blower - the range hood blower is located inside of the range hood canopy
• Inline to the duct run - the range hood blower is located somewhere along the range hood exhaust ducting
• External to the range hood - the range hood blower is located either on the roof or on an external wall

Internal range hood blower

External range hood blower

Inline range hood blower

If the cooking equipment - the stove or the range dicatate (based on the btu to cfm calculation that can be found on posts in this blog) that around 600cfm is required then there is not a great deal of benefit to be achieved by placing the range hood blower remote from the range hood canopy

Noise is one of the main reasons why remote blowers for range hoods are installed. If the range hood blower, whether inline or external is close to the range hood very little benefit in term so of noise reduction will be achieved.

An external blower mounted on the wall directly behind the range hood without any bends in the duct run will not help the noise a great deal.

For optimal noise reduction from an external blower there should be at least one 90 degree bend in the duct run.

For optinal noise reduction a duct silencer system can be placed in the duct run.

Duct silencers

What the Home Ventilation Institute(HVI) has to say about range hoods

PS31 SP Textured Black

 

Kitchen Range Hoods:

A kitchen range hood must move more air than a bathroom fan. about 50 to 140 L/s (100 to 300cfm) as a minimum. As a result, they are noisier, with the lowest rating about 4.5 sones, although they can be

relatively quiet on low speed.
The most useful units have a low noise rating, an energy-efficient fan, fluorescent lights, sound
insulation, anti-vibration mounts and duct connections. For heavy duty use, select non-corrosive
materials such as aluminum or stainless steel. High quality hoods may have heat sensors and a
safety shut-off.
Kitchen exhaust systems should discharge outdoors. Recirculating range hoods rely on filters to
capture some odours and grease. The filters are generally made of carbon which must be
replaced frequently to be effective. Grease will coat carbon, making it ineffective. With
recirculating fans, cooking moisture and odours will usually remain in the house.

Positioning:

Range hoods are most effective when they extend out over the stove surface and are close to the
stove top. Island units are less effective than wall units.

Cleaning:

Range hoods usually have washable, aluminum-mesh grease filters. Better quality filters have a
smaller diameter mesh over a larger surface area and can be cleaned in the dishwasher.

Fire:

There is always the possibility of a grease fire with a kitchen range hood exhaust. Smooth metal
ducting, preferably galvanized steel, is safer in a fire than lighter assemblies.

Installation:

Install fans and exhaust systems so they make the least possible noise, vibrate as little as possible
and leak as little air as possible.
Anti-vibration pads or foam tape can isolate the fan housing from wood joists and drywall. You
can wrap fan housings and some duct sections in rubber or vinyl noise barrier mats.
DuctsInstall exhaust systems according to the building code and manufacturer's recommendations.
Straight, short duct runs, with few turns, will result in the highest fan flow