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

Over the range microwave hoodfan vs range hood

What are the differences between an OTR vs a dedicated range hood.

Over the range micorwave:
 PRO'S:

• Saves space in small kitchens where counter top space is limited
• Its convenient location above the stove
• CFM (cubic feet per minute) is low - limits negative air pressure in the home

CON'S:

• Typically very noisy as a hoodfan
• Does not provide coverage over all cooking elements - so vapours from front burners are'nt captured
• Poor grease filters
• If vented externally then ducting is typically small and cfm is low - not a good situation if being used over say a gas range
• CFM - cubic feet per minute of airflow is typically low - this is okay if over say a basic 30" electric top
• Most OTR's are re-circulating and require constant charcoal filter replacement
• Very low height over the range - "sort of" in your face
• Typically difficult to keep clean because they are so close to the range top and get greasy quickly

Range Hood:
PRO'S:

• If installed and sized to the range correctly these range hoods provides optimal extraction and disposal of those dangerous cooking vapours
• Range hoods are typically visually appealing and enhance the design and look of the kitchen
• These range hoods are easy to clean and the range hood filters come out easily for cleaning

CON'S:

• Range hoods require a dedicated space above the range
• A half decent range hood generally costs more than a good over the range microwave

Our latest happy customer

Ken and Charmaine love their new range hood as much as they love their new kitchen

PS15SP 54" wide by 28" high Oil rubbed bronze with

brushed stainless steel trim and a 1000cfm externally

mounted blower 

Does your range hood perform as well as it should

Here are a few of the typical issues that consumes encounter with their range hoods and a brief look at why these issues may exist:

Problem = NOISY RANGE HOOD
Result = You don't use the range hood and the grease, vapors are spreading through your home

• The ducting is restricted
• This could be as a result of a back draft damper flap that is jammed in place creating back pressure on the blower - like all things in nature the blower responds and pushes back by increasing its effort
• The ducting is to small for the range hood blower
• Same situation as above - the rangehood blower works harder to get push the air out
• Filters are blocked - usually the case with mesh filters where the grease has congealed and the air cannot pass through easily
• Clean the venthood filters - if they are dishwasher safe - dishwasher otherwise by hand with a powerful detergent
• A cheap motor - as with most things in this world there are varying degrees of quality and a badly balanced and cheaply built range hood blower will make a great deal of mechanical noise

Problem =SMOKE AND COOKING FUMES ARE NOT BEING SUCKED IN BY THE RANGE HOOD
Result = Grease, vapors and odors spread through your home

• Blocked filters as above - this very rarely happens with baffle filters, it mostly happens with mesh filters
• Clean the filters
• The range hood blower system is under powered relative to the stove or range - in ventilation terms it is not drawing sufficient cfm(cubic feet per minute of air) to handle the volume of smoke or vapor being created by the range - very often happens over ranges with bbq's or griddles.
• Not much you can do except change the range hood blower - this has other implications - is the range hood ducting large enough to cope with the increased cfm - there is a correlation between cfm and range hood duct size - see other posts on this blog
• The capture area formed by the range hood does not cover the burners - when hot vapor rises it expands outwards like a funnel - if the range hood doesnt at least cover the burners you will have this problem
• Not much you can do again except a mjor reno and replace the range hood so that it covers the burners.
• A case in point - we were called to a consumers house who had a 48" wide by 27" deep wolf range with bbq - the client loved to bbq. However the hood above the range was only 14" deep - it was/is a beautiful 72" wide custom cabinet mantel hood. This was a big problem - not only are there no inserts on the market that are around 14" shallow by 48" wide there just is not the coverage - we came up with a solution for them - we bulit a custom 14" deep by 72" wide custom insert with baffle filters and only had baffle filters over the 48" space - we then added a 1000cfm external blower to the mix which creates a huge amount of negative air pressure through the filters - not a 100% solution but pretty close - most of the bbq work must be done at the back of the bbq. Picture doesn't show the whole story but there it is.

• Maybe you have a microwavehood - these typically suck in the air and then blow it back into the room - these are called re-circulating hoods - not much to say about these that is positive.

If you have any questions or live with these problems feel free to contact us - we provide advice and suggestions free of charge.

Range hood Noise and how to manage it

The critical factors in noise reduction are:

-          Type of filters

-          Quality of duct work – appropriate size for the airflow, length and number of bends

-          Quality and size of blower used

Filters:

There are in essence two types of filters – mesh and baffle. Baffle filters are quieter, 96% efficient and excellent fire travel blockers. Mesh are only recommended in lower cfm applications around 400cfm to 600cfm and over electric style cook tops.

Quality of ductwork:

The most critical element is the size and quality of duct material relative to the maximum airflow you try to move down that duct – for 400cfm internal blowers we recommend 7”, for 600cfm internal blowers 8” and 1200cfm internal blowers 10”. Inline blowers between 600 and 1000cfm need 8” duct and external blowers of 1000cfm 8” duct. Rigid metal duct is strongly recommended – flexible ribbed ducting will be noisy because the air is “tripping” of the ridges and makes noise.

The average duct length and number of bends found today is not too much of an issue – if bends and length is excessive then external blowers and more powerful blowers should be used – if a blowers is trying to “PUSH” a high volume of air down a long and wavy duct run the motor needs to work harder and of course will be noisier.

Blowers:

These  come in all forms of quality – the quality blowers have less mechanical noise because they are well made and balanced.

An internal range hood blower

An external range hood blower

roof or wall mount

An inline range hood blower

http://www.customrangehoods.ca/