question about adding a flex ducting run


  #1  
Old 03-19-06, 02:46 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
Received 0 Votes on 0 Posts
question about adding a flex ducting run

Hi all,

My current furnace setup is all flex ducting thru the house. The furnace is located in the attic, as is all the ducting. Registers are ceiling mounted. Currently there are 8 branches off the main trunk.

Recently completed an addition, and I'd like to add a ducting run. The truck is relatively close to the addition; I'd need a run of a bout 10 feet to get there.

The installation seems pretty straightforward, but I"m sure there ae some things I need to verify first prior to determining location of the cut-in, flex duct diameter, and anything else I'm missing.

Thanks for any advice, in advance.
 
  #2  
Old 03-19-06, 08:31 PM
T
Member
Join Date: Dec 2005
Posts: 458
Received 0 Votes on 0 Posts
What size is your house, your addition and your system? Normally, one run is not sufficient for an addition.
 
  #3  
Old 03-19-06, 08:40 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
Received 0 Votes on 0 Posts
house without the addition is a 3/2, around 1100 sq. ft. The addition is only 1 room, which is approx. 13/20, so let's say 260 sq. ft.

My furnace is new as of last winter. I'm looking at the manual, and forgive me for not being specific but HVAC is new to me. Here is what I see:

Looks like it's a UPG/York Model LY8S, Single Stage 80% Downflow...?


Probably need to look on the unit itself to determine the CFM's??

Thanks for any help you all can provide.


My original plan is to run the new duct from the furnace, thru the garage, and then into the addition and position the register about 1 ft from the ceiling. The way the addtion is built, there is no floor or ceiling access. The only other option is to run the duct thru a wall, but the only wall available is one that used to be the outside of the house years ago, so it's load bearing (I would assume)

And thoughts and advice is welcomed. Thanks !!
 

Last edited by fuente; 03-19-06 at 08:58 PM.
  #4  
Old 03-21-06, 05:10 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
Received 0 Votes on 0 Posts
top. anyone?
 
  #5  
Old 03-22-06, 10:41 AM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,386
Received 0 Votes on 0 Posts
Wink

My original plan is to run the new duct from the furnace, thru the garage, and then into the addition and position the register about 1 ft from the ceiling
If its a long way you might have to make the supply pipe bigger

The only other option is to run the duct thru a wall, but the only wall available is one that used to be the outside of the house years ago, so it's load bearing (I would assume)
[/QUOTE] You could cut the wall between two studs for a register and that wont hurt it/

ED
 
  #6  
Old 03-22-06, 10:54 AM
F
Member
Thread Starter
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
Received 0 Votes on 0 Posts
Thanks Ed. I guess I'd nee to know what 'a long way' is; I'm looking at a duct running approximately 25 feet if I go thru the garage. If I cut thru the load bearing wall, it brings it down to approximately 10-15 feet.

Thanks. Is there a link that would step me thru the process of cutting into the duct and adding a new one?
 
  #7  
Old 03-22-06, 08:02 PM
T
Member
Join Date: Dec 2005
Posts: 458
Received 0 Votes on 0 Posts
You should probably add 2 ducts. If you go through the load bearing wall just go between the studs and its ok. Add a big return. Close to the ceiling is best. If you can get the supplies to the floor level thats great.
 
  #8  
Old 03-22-06, 08:26 PM
F
Member
Thread Starter
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
Received 0 Votes on 0 Posts
Originally Posted by thermofridge
You should probably add 2 ducts. If you go through the load bearing wall just go between the studs and its ok. Add a big return. Close to the ceiling is best. If you can get the supplies to the floor level thats great.
I'm assuming when you say two ducts, one is for supply and one is for return. The house only has one return ,and it's in the middle of the hallway. No other area has a return. The addition is near the return, via a hallway and pass thru window to the kitchen.

Would I still need to add a return? I can't add a return to the ceiling, as there is no access. And I cannot get the suppy to the floor level; it would have to be on the wall, near the ceiling, due to the nature of the addition.

The room is only really cold in the mornings. We live in CA near San Francisco, so our climate is pretty mild. Any heat we can get in the room, even if it only raises the temp 5-10 degrees, would be comfortable.

Thanks again for all the advice. It's good to know I can go thru the wall. What size ducting would I need, and how would I go about cutting into the main trunk?

Also, is it acceptable to make the new run come off an existing branch, and not the main trunk? If this is do-able, the run would only be 3-5 feet. I can put it right off the line going to the kitchen.

Thanks.
 

Last edited by fuente; 03-22-06 at 08:44 PM.
  #9  
Old 03-23-06, 04:21 AM
E
Member
Join Date: Jul 2005
Location: Ottawa, Canada
Posts: 857
Received 0 Votes on 0 Posts
Originally Posted by fuente
Thanks for any advice, in advance.
Don't use flex duct as it dramatically reduces the air flow which increases the load on your furnace thereby reducing it's life expectency.

If all of your ducts are accessible in your attic, then you should changed them all to metal ducts while you are up there.

Flex duct has no real purpose and adds no value.
 
  #10  
Old 03-23-06, 06:49 AM
F
Member
Thread Starter
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
Received 0 Votes on 0 Posts
Originally Posted by em69
Don't use flex duct as it dramatically reduces the air flow which increases the load on your furnace thereby reducing it's life expectency.

If all of your ducts are accessible in your attic, then you should changed them all to metal ducts while you are up there.

Flex duct has no real purpose and adds no value.
Thanks for the input, but I don't plan on being in the house for much longer, and the house isn't that big. Just trying to get a little air into this one room. I know flex is inferior to metal, but at this time I don't what to replace everything. Maybe in the future, but not right now.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: