Thermador recommends an additional inline backdraft damper for cold weather
installations. From page 4 of their installation manual:

COLD WEATHER installations should have an additional
backdraft damper installed to minimize backward cold air
flow and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.
The damper should be on the cold air side of the thermal
break. The break should be as close as possible to where
the ducting enters the heated portion of the house.

Now from reading this it appears that this is in addition to the damper
that will be on the wall cap. I would think that Brooklyn qualifies as a
cold weather installation.

Do people here think having two dampers makes sense? It will restrict the
air flow some, though the fan currently spec'd is 1,000 CFM, which should
be ample.

The wall cap I plan to use is the 10" he
http://www.luxurymetals.com/coppervents.html#anchor_423

A butterfly backdraft damper candidate is he
http://www.luxurymetals.com/butterfl...ft_damper.html

Don. www.donwiss.com (e-mail link at home page bottom).

Don Wiss wrote:
Thermador recommends an additional inline backdraft damper for cold weather
installations. From page 4 of their installation manual:

COLD WEATHER installations should have an additional
backdraft damper installed to minimize backward cold air
flow and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.
The damper should be on the cold air side of the thermal
break. The break should be as close as possible to where
the ducting enters the heated portion of the house.

Now from reading this it appears that this is in addition to the damper
that will be on the wall cap. I would think that Brooklyn qualifies as a
cold weather installation.

Do people here think having two dampers makes sense? It will restrict the
air flow some, though the fan currently spec'd is 1,000 CFM, which should
be ample.

The wall cap I plan to use is the 10" he
http://www.luxurymetals.com/coppervents.html#anchor_423

A butterfly backdraft damper candidate is he
http://www.luxurymetals.com/butterfl...ft_damper.html

Don. www.donwiss.com (e-mail link at home page bottom).

Hi,
I'm in Calgary AB, Usually flap in the exterior cap is all common,
nothing additional. 1000CFM? If the blower is good one, it could be
quite noisy. More added things, more chance of getting trouble, LOL!

On Wed, 13 Aug 2014 09:51:33 -0600, Tony Hwang wrote:

I'm in Calgary AB, Usually flap in the exterior cap is all common,
nothing additional. 1000CFM? If the blower is good one, it could be
quite noisy. More added things, more chance of getting trouble, LOL!

Calgary is a lot colder than here!

It will be a Thermador. I expect I would rarely run it at full speed.

Don. www.donwiss.com (e-mail link at home page bottom).

On 8/13/2014 11:42 AM, Don Wiss wrote:
Thermador recommends an additional inline backdraft damper for cold weather
installations. From page 4 of their installation manual:

COLD WEATHER installations should have an additional
backdraft damper installed to minimize backward cold air
flow and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.
The damper should be on the cold air side of the thermal
break. The break should be as close as possible to where
the ducting enters the heated portion of the house.

Now from reading this it appears that this is in addition to the damper
that will be on the wall cap. I would think that Brooklyn qualifies as a
cold weather installation.

Do people here think having two dampers makes sense? It will restrict the
air flow some, though the fan currently spec'd is 1,000 CFM, which should
be ample.

The wall cap I plan to use is the 10" he
http://www.luxurymetals.com/coppervents.html#anchor_423

A butterfly backdraft damper candidate is he
http://www.luxurymetals.com/butterfl...ft_damper.html

Don. www.donwiss.com (e-mail link at home page bottom).


We have flaps on exhaust vents.
Just had experience of birds stuffing our drier vent with nesting
materials where one of vent flaps is slightly warped and birds got in.
Could have caused a fire with all the stuff we had to clean out. I
capped it with a bird nest cage.
So even if warm, back draft dampers can be a good idea.

On Wed, 13 Aug 2014 11:42:02 -0400, I wrote:

and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.

I was starting to research Thermador's suggestion of a nonmetallic thermal
break. Like what to call it so I can buy such an item. And I found someone
has asked the same question I'm asking:

http://www.diychatroom.com/f47/range...climate-90906/

Don. www.donwiss.com (e-mail link at home page bottom).
Don. www.donwiss.com (e-mail link at home page bottom).

Don Wiss wrote:
On Wed, 13 Aug 2014 11:42:02 -0400, I wrote:

and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.

I was starting to research Thermador's suggestion of a nonmetallic thermal
break. Like what to call it so I can buy such an item. And I found someone
has asked the same question I'm asking:

http://www.diychatroom.com/f47/range...climate-90906/

Don. www.donwiss.com (e-mail link at home page bottom).
Don. www.donwiss.com (e-mail link at home page bottom).

Plastic.

Greg

On Thu, 14 Aug 2014 07:19:45 +0000 (UTC), gregz wrote:

Don Wiss wrote:
On Wed, 13 Aug 2014 11:42:02 -0400, I wrote:

and a nonmetallic thermal break to minimize
conduction of outside temperatures as part of the ductwork.

I was starting to research Thermador's suggestion of a nonmetallic thermal
break. Like what to call it so I can buy such an item. And I found someone
has asked the same question I'm asking:

http://www.diychatroom.com/f47/range...climate-90906/

Plastic.

Well, I can't simply search on plastic. A search term is what I was asking
for. Where do I find a 10" round plastic tube?

Don. www.donwiss.com (e-mail link at home page bottom).

On Wednesday, August 13, 2014 12:07:42 PM UTC-4, Don Wiss wrote:
On Wed, 13 Aug 2014 09:51:33 -0600, Tony Hwang wrote:



I'm in Calgary AB, Usually flap in the exterior cap is all common,

nothing additional. 1000CFM? If the blower is good one, it could be

quite noisy. More added things, more chance of getting trouble, LOL!



Calgary is a lot colder than here!



It will be a Thermador. I expect I would rarely run it at full speed.



Don. www.donwiss.com (e-mail link at home page bottom).

I'd say a key factor is also how windy it is at the location.
If it's an area of extreme temps and high winds, then I can see
using a double flapper approach. Otherwise, I would be more concerned
about the increased flow resistance than I would about the loss from
occasional gusts that might push the flap open.

Personally, I've never seen an installation with more than one.

But, if done properly, would you ever actually see the second damper?

On Thu, 14 Aug 2014 20:46:20 -0700 (PDT), wrote:

But, if done properly, would you ever actually see the second damper?

No. All ductwork will be inside the cabinets.

I did find a nonmetallic thermal break to put in the ductwork. I can buy 2"
of this 10" PVC pipe for a few dollars:
http://flexpvc.com/cart/agora.cgi?pr...-DUCT-Thinwall

Don. www.donwiss.com (e-mail link at home page bottom).