For venting: 640 CFM range hood or 630 inline blower?
 

Ok, total amateur here, trying to set up an inexpensive, but effective vent system.

I have done all the calculations, and I think I need for a 30"x20" range hood size hood: 5 feet of 6" ducting with 2 ninety degree elbows:
around 600CFM blower/fan.

I have found brand new high-drawing range hoods between 630 CFM and 700 CFM for $120 to $135.

I have also found an inline blower at 630 CFM designed for venting hydroponic greenhouses, lightly used for $150 to $175.

Do you think the 630 or 700 Range Hood with 6" ducting will work for a ventilation system? Do they draw as much as they are rated to?

Rangehoods are Milano brand and Cyclone brand - don't know either company - don't know if they are knockoffs at this price, but they have no side baffles, so I will be adding them.

Inline fan is Ostberg brand.

Any thoughts?
TIA

p.s. I'm in Canada and it seems hard to find reasonably priced inline fans - especially squirrel cage - for a good price!

What kind of torch? I'd spend the extra 150.00 and get the 1000 cfm if it were me. There are several on EBAY. 2 ninety degree elbows is going to really hurt the performance.

Just a HotHead.

Yeah, with 2 90 degree bends it will drastically reduce the amount of draw. No matter what the fan is rated, you won't be getting near that. Shoot for the 1000 cfm to make up for the elbows.