We are installing a new DSC gas range and VentaHood with the dual fans
(600cfm) to go over it. Because of the location, it is very difficult
to run a duct to the outside. Our contractor suggested getting a
back-venting model and running a duct (rectangular?) down through the
wall into the crawlspace and then laterally out. Does this make
sense? It will be about a 17 foot run (4 feet down, 13 feet across).
Do these things have to be vented in the upward direction only, or it
doesn't matter as long as the fan is strong enough and there aren't
too many "bends"?

Thanks for any suggestions.

-Morgan

(Morgan) wrote in message . com>...
> We are installing a new DSC gas range and VentaHood with the dual fans
> (600cfm) to go over it. Because of the location, it is very difficult
> to run a duct to the outside. Our contractor suggested getting a
> back-venting model and running a duct (rectangular?) down through the
> wall into the crawlspace and then laterally out. Does this make
> sense? It will be about a 17 foot run (4 feet down, 13 feet across).
> Do these things have to be vented in the upward direction only, or it
> doesn't matter as long as the fan is strong enough and there aren't
> too many "bends"?
>
> Thanks for any suggestions.
>
> -Morgan

Have you checked here?

http://www.ventahood.com/Specs%20Ins...%20Install.htm

Rob

(Morgan) wrote in message . com>...
> We are installing a new DSC gas range and VentaHood with the dual fans
> (600cfm) to go over it. Because of the location, it is very difficult
> to run a duct to the outside. Our contractor suggested getting a
> back-venting model and running a duct (rectangular?) down through the
> wall into the crawlspace and then laterally out. Does this make
> sense? It will be about a 17 foot run (4 feet down, 13 feet across).
> Do these things have to be vented in the upward direction only, or it
> doesn't matter as long as the fan is strong enough and there aren't
> too many "bends"?
>
> Thanks for any suggestions.
>
> -Morgan


Morgan --

1. As to the general question whether a rangehood has "to be vented
in the upward direction only"? The answer is no. For similar
reasons, we vented our rangehood as your contractor suggested. The
duct comes out of the back of the rangehood, runs inside the wall
(using rectangular duct), through the floor into the basement, across
the basement ceiling (it's 8" round duct at this point), and outside
through a window. Ducting run is around 20 feet overall, plus a
couple of bends.

Is this the most efficient routing? Of course not. But it works just
fine. We did get a more powerful hood than the usual formula would
otherwise suggest to compensate for the less-than-ideal run -- and the
other aspects of the installation are also all along the preferred
lines. We've had it up and running for about two months, and I'm
satisfied.

2. Some details. The hood is over a 30" Blue Star rangetop. Total
BTU is 66,000. Conventional wisdom says take total BTU and divide by
100 to get CFM (so that's 66,000/100 = 660 CFM). We got a 900 CFM
dual blower hood to try to compensate for the routing. Plus the hood
is mounted at 30" above the cooking surface (more or less the
preferred height) and the hood is 36" wide, also following the
preferred rule of 6" wider than the range/rangetop. The hood we got
is a Best by Broan K210A (that's a 10" high, under-cabinet, pro-style
hood) with the dual P8 in-cabinet blower. (Could also get a remote
blower instead, if you prefer.) The Best K210A (at 10" high, 22" deep)
is basically a slightly smaller version of the K260A (at 18" high, 24"
deep); the K260A would have been too tall for our cabinet arrangment.

3. One advantage of the Best hood is that it does allow you to run
the ducting directly out the back of the unit, rather than only out
the top. This eliminated one sharp bend -- plus it means that we lost
no space in the cabinet above the hood (as ducting goes directly into
wall). I believe Thermador under-cabinet Pro-Style hoods also vent
out the back (as well as the top).

4. I think the Vent-A-Hood specs are saying that the ducting can only
run out of those units from the top, and not the back. That would not
be preferable if you then want to run the ducting downwards (as it
adds an extra bend). There is more or less continual debate about
Vent-A-Hoods in the appliance forum at the gardenweb site
(www.thathomesite.com). Many love them -- and, in particular, claim
they are quieter than other hoods. Others worry about cleaning them
(as there are no filters). The Best by Broan is resonably quiet (for
an inherently noisy appliance) at lower to mid fan-speed settings and
reasonably loud at upper mid to high speeds; I haven't needed to use
the latter yet to get the job done.

Hope this helps.

Thank you for a thorough and well written reply. We are currently
considering re-modeling the entire kitchen and may move the range
location so that venting is easier. But if not, we will go for the
down ducting and make sure we get a proper hood. Thanks again.

-Morgan


(MEM9) wrote in message om>...
> (Morgan) wrote in message . com>...
> > We are installing a new DSC gas range and VentaHood with the dual fans
> > (600cfm) to go over it. Because of the location, it is very difficult
> > to run a duct to the outside. Our contractor suggested getting a
> > back-venting model and running a duct (rectangular?) down through the
> > wall into the crawlspace and then laterally out. Does this make
> > sense? It will be about a 17 foot run (4 feet down, 13 feet across).
> > Do these things have to be vented in the upward direction only, or it
> > doesn't matter as long as the fan is strong enough and there aren't
> > too many "bends"?
> >
> > Thanks for any suggestions.
> >
> > -Morgan
>
>
> Morgan --
>
> 1. As to the general question whether a rangehood has "to be vented
> in the upward direction only"? The answer is no. For similar
> reasons, we vented our rangehood as your contractor suggested. The
> duct comes out of the back of the rangehood, runs inside the wall
> (using rectangular duct), through the floor into the basement, across
> the basement ceiling (it's 8" round duct at this point), and outside
> through a window. Ducting run is around 20 feet overall, plus a
> couple of bends.
>
> Is this the most efficient routing? Of course not. But it works just
> fine. We did get a more powerful hood than the usual formula would
> otherwise suggest to compensate for the less-than-ideal run -- and the
> other aspects of the installation are also all along the preferred
> lines. We've had it up and running for about two months, and I'm
> satisfied.
>
> 2. Some details. The hood is over a 30" Blue Star rangetop. Total
> BTU is 66,000. Conventional wisdom says take total BTU and divide by
> 100 to get CFM (so that's 66,000/100 = 660 CFM). We got a 900 CFM
> dual blower hood to try to compensate for the routing. Plus the hood
> is mounted at 30" above the cooking surface (more or less the
> preferred height) and the hood is 36" wide, also following the
> preferred rule of 6" wider than the range/rangetop. The hood we got
> is a Best by Broan K210A (that's a 10" high, under-cabinet, pro-style
> hood) with the dual P8 in-cabinet blower. (Could also get a remote
> blower instead, if you prefer.) The Best K210A (at 10" high, 22" deep)
> is basically a slightly smaller version of the K260A (at 18" high, 24"
> deep); the K260A would have been too tall for our cabinet arrangment.
>
> 3. One advantage of the Best hood is that it does allow you to run
> the ducting directly out the back of the unit, rather than only out
> the top. This eliminated one sharp bend -- plus it means that we lost
> no space in the cabinet above the hood (as ducting goes directly into
> wall). I believe Thermador under-cabinet Pro-Style hoods also vent
> out the back (as well as the top).
>
> 4. I think the Vent-A-Hood specs are saying that the ducting can only
> run out of those units from the top, and not the back. That would not
> be preferable if you then want to run the ducting downwards (as it
> adds an extra bend). There is more or less continual debate about
> Vent-A-Hoods in the appliance forum at the gardenweb site
> (www.thathomesite.com). Many love them -- and, in particular, claim
> they are quieter than other hoods. Others worry about cleaning them
> (as there are no filters). The Best by Broan is resonably quiet (for
> an inherently noisy appliance) at lower to mid fan-speed settings and
> reasonably loud at upper mid to high speeds; I haven't needed to use
> the latter yet to get the job done.
>
> Hope this helps.

MEM9 > wrote:

4. I think the Vent-A-Hood specs are saying that the ducting can only
> run out of those units from the top, and not the back.

I had VAH add their "lowered blower deck" option to my 18" tall Emerald
model, so that I could have a rear duct (directly through the outside
wall on which the hood is hung.) The lowered deck drops the "ceiling"
of the hood nine inches, making the hood only nine inches tall inside.

The upper nine inches is open space, which allows one to use VAH's
90-degree elbow to cause a rear exit from the hood. The entire elbow is
invisible from the room.

The only drawback is that one has a smaller volume within the hood, but
this has never been a problem for me. Even with high-heat cast-iron
searing, the blowers empty the hood canopy with easy.

General kitchen photos, with views of the hood in place at
http://www.cfcl.com/rick/pix/finished.html

Detailed hood photos, showing the ducting, at
http://www.cfcl.com/rick/pix/hood/

--
- rick http://www.cfcl.com/~rick/
Rick Auricchio Macs Only: Macintosh support
I acknowledge the existence of a higher power, and have therefore installed
surge suppressors.

Thanks for the lengthy reply and indeed it answers my query. Both Morgan and i have actually the same predicament about Vent-A-Hood range hood.

Range hood technician/contractor knows best when it comes to duct installation since they are the experienced ones compared to us.