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pvsorge 10-08-2008 02:43 PM

Duct work patch
 
Hi, I recently purchased an older home (1929) that was retro fitted with flexible ductwork in the attic. In order to provide heat/ac to a sunroom, the previous owner ran the "flex" duct work through the closet in the master bedroom. I know very little about HVAC, but I'm avid DIYer (I know my limits as well). The duct work takes up half the closet and I want to replace that piece with a smaller diameter, solid duct to free up the much needed closet space.

It important to point out that the room this duct supplies in used very little in the winter, but I still need some heat. What would be the best way to remedy this problem?

Marvin Gardens 10-08-2008 04:00 PM

Smaller means less air which means less heat/cool in the room it serves. Think real hard before you go through with this.

1610 CUB 10-08-2008 06:11 PM

pvsorge, If the flex duct is 6", 7" or 8" you can get those sizes in oval pipe sizes. an oval pipe can take up space wile not hurting the CFM to the room it services. ( An 8" oval off the top of my head is 3.125"X10") Any sheet metal shop can get you oval pipe and fittings, I hope this is some help... j

Reilley 10-08-2008 08:33 PM

Quote:

Originally Posted by Marvin Gardens (Post 169763)
Smaller means less air which means less heat/cool in the room it serves. Think real hard before you go through with this.

Naturally. However when replacing flex duct with regular sheet metal duct the sheet metal duct of about 1/2 to 2/3 the size would provide the same amount of flow as the crappy flexible stuff.

Marvin Gardens 10-08-2008 09:00 PM

Quote:

Originally Posted by Reilley (Post 169883)
Naturally. However when replacing flex duct with regular sheet metal duct the sheet metal duct of about 1/2 to 2/3 the size would provide the same amount of flow as the crappy flexible stuff.

That is true plus no insulation to take up space. Round is always better than square for moving air though.

dac122 10-09-2008 07:51 AM

Please post the diameter size flex duct you have. I can look up the equivalent galvanized circular or oval in the Manual D friction charts so your CFM doesn't change. Flex usually has more friction so you can downsize when switching.

If you are looking to replace the entire run in an unconditioned attic space you will want to insulate the duct.

pvsorge 10-09-2008 08:49 AM

Duct work patch
 
Thank you for all the useful replies.

The flex duct is 7". The main issue is this: The 7" flex duct runs from the attic, through the center of the closet, turns, and then goes into the wall where it connects to the register in the cieling. Basically taking up half of the closet in the master BR. This duct provides heat/AC to a sun room addition that was at one point a screened in porch. As such, we generally don't use the room in the dead of winter. The air flow to that room now, is terrible at best without and modification. The whole configeration defies logic. I'm fully aware that at some point I'll need a pro HVAC person to come in and do some major upgrades to the whole system. With that being said, I'm mostly looking to free up much need closet space without causing any major airflow issues to other areas in the system until I can get(affford) a professional to come in. As a side note, this is my wifes closet. To anyone who is married, I'm sure you don't need any more details.

Thanks for all your great insight!

dac122 10-09-2008 09:30 AM

A 6" galvanized circular should be equivalent. You will probably have to go to a specialty heating place to get the oval, so tell them you need 6" galvanized circular equivalent.

Since you are saying the flow is terrible now it is possible the size and where it taps your system was wrong from the beginning.

chatterbass 10-09-2008 10:27 AM

Can you post a pic of what you have. I am sure ther is a couple of ways you can go about it. Also there is a few things you should check before starting. One is make sure the damper on the main trunk is open . This could be one of the restrictions you are having. Also depending on the room you have and you mechanical capibilitys you can probally free up a good amount of space.

pvsorge 10-09-2008 11:33 AM

Thanks for the advice. I will post a picture ASAP.

My guess, based on your replies is that something can be done temporarily.

Thanks again for all your help.


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