[limiteddi]

Greetings,

I was about to start installing my range hood and noticed something that threw me off. The unit has a capability on speed 4 to operate at 1200CFM but the duct size is only 8". I was looking at various charts and it doesn't look like 8" will produce enough airflow room for 1200CFM? We never have more than 2 burners on.

Here is the unit.
https://www.canadianappliance.ca/pdf/elica/ventilation/ELN136S2_installation-instruction.pdf

Can someone shed some light in regards to the sizing of the duct in this case?

 

[user_12345a]

The CFM ratings for hoods don't reflect what happens in the real world.

The hoods are rated at ridiculously low duct pressure - sometimes with no duct at all connected.

It's not necessary to have 1200 cfm for a range, if it moves even 400 cfm you're more than good.

Having the velocity and pressure high helps with preventing grease from getting deposited in the duct.

Even if it moves 400 cfm you'll need to open a window when it's in use or have dedicated make-up air if you have any natural draft appliances.

 

[roughneck]

What do you plan on doing for makeup air?

 

[Bud9051]

Page 5 of the link you provided says:
6 . Make up air: Local building codes may require the use of Make-Up Air Systems when using Ducted Ventilation Systems greater than specified CFM of air movement. The specified CFM varies from locale to locale. Consult your HVAC professional for specific requirements in your area."


The typical threshold (U.S.) is 400 CFM. I don't know what Canada requires or what your local code official wants. As User mentioned "if you have any natural draft appliances." then there is a risk of backdrafting.


Bud