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Ducting inside a wall for a hood for Bluestar RNB 36?
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Posted by frenchman (My Page) on Thu, Nov 19, 09 at 16:43
| I am toying with the idea some gentleman expressed here of hiding a hood under/within cabinets and having the ducting go inside a wall that we're building this weekend and that the range will be against.
I would want an inline blower in the attic. What size ducting should I expect to use? It seems that it's 10" or 8". That ducting would then have to be connected to a rectangular duct that could go inside the wall. Is there such a duct that would still provide enough capacity? Finally, the duct would end flush with the wall or inside a cabinet. Would that reduce the effectiveness of the blower or increase noise a lot? (I imagine that either the opening is at the wall, resulting in a "horizontal" sucking, or boxed in somehow, and would that count as a bend?)
Thanks!
YA |
Follow-Up Postings:
RE: Ducting inside a wall for a hood for Bluestar RNB 36?
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| Ten inches is extremely large. (Too large is a possibility.) Pi times R squared for a 10" or 8" round duct is about 80 or 50 square inches. A rectangular duct has about 90 to 60 square inches cross area. That is greater. Then, removing a bit since there will be a little more friction loss since there is more metal for the air to rub against, (more than in a round duct), you get a result in the same range as the 10" or 8" round duct. More or less, give or take, rounded out to the nearest, etc, plus or minus ten percent, etc. An inline blower in the attic means that your transitioning from rectangular to round will not require elbows (bends), or maybe one 135-degree bend. This means there are not any significant friction losses. Sounds like it could be a feasible plan. |
RE: Ducting inside a wall for a hood for Bluestar RNB 36?
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| Thanks. If doing 8" (I don't want to overbuild anything), should I still go for a 1200 CFM blower? (I used Modern Aire's site as my reference and they say "total BTUs / 100 ~ CFM" and the RNB 36 puts out 113,000---which includes the oven, so let's say 98,000 w/o it). The Fantech 1200 comes as a 10" (with 8" adapters IIRC). YA |
RE: Ducting inside a wall for a hood for Bluestar RNB 36?
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| If you go 1200 CFM, then you probably should go with 10" round, or equivalent. For a BlueStar 6-burner (no grill), you are probably OK with a 600 CFM internal pack on a hood the quality of a Modern-Aire, Prestige, or Independent. The Fantech would not be overkill. If you are working with a semi-custom hood manufacturer, I'd call their support team and discuss your install with them. I've talked with both Modern-Aire and Prestige and both have been very helpful even in pre-sales planning. |
RE: Ducting inside a wall for a hood for Bluestar RNB 36?
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| I'm installing a 1200 cfm internal blower on the Prestige/Bluestar hood (36") with the 30" BlueStar. The overkill factor is somewhat mitigated by the 8" duct (all I could fit) but the reasoning is that if I DO need to crank up the CFMs then I will have the ventilation power and let the noise be damned. I am hoping that for normal use I will run the hood on low and the duct size should be more than adequate. It was very inexpensive (via Trevor at Eurostoves) to upgrade to the larger blower. I did call Prestige, and they agreed with Trevor that 8" duct, though maybe not absolutely ideal, should basically be OK for their 1200 CFM internal blower :). |
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