Has anyone seen?? - Contractor Talk - Professional Construction and Remodeling Forum

jarvis design · 01-18-2009, 11:50 AM

I just put a post up regarding exhaust fan venting and forgot to ask if anyone has seen 4" smooth plastic pipe and elbows.

I currently use galvanized, but think that a rigid plastic pipe would be better - less thermal transfer/condensation

Anyone seen anything like that??

rbsremodeling · 01-18-2009, 11:52 AM

Quote:

Originally Posted by jarvis design

I just put a post up regarding exhaust fan venting and forgot to ask if anyone has seen 4" smooth plastic pipe and elbows.

I currently use galvanized, but think that a rigid plastic pipe would be better - less thermal transfer/condensation

Anyone seen anything like that??

what kind of exhaust fan kitchen or bath?? Why can't you use PVC

jarvis design · 01-18-2009, 11:59 AM

Quote:

Originally Posted by rbsremodeling

what kind of exhaust fan kitchen or bath?? Why can't you use PVC

The majority of my work is bathrooms and 95% of the time I use Panasonic exhaust fans. When you say PVC, what thickness of pipe wall are you referring to??

rbsremodeling · 01-18-2009, 12:05 PM

Quote:

Originally Posted by jarvis design

The majority of my work is bathrooms and 95% of the time I use Panasonic exhaust fans. When you say PVC, what thickness of pipe wall are you referring to??

3 or 4 inch schedule 40 pvc pipe

jarvis design · 01-18-2009, 12:56 PM

Quote:

Originally Posted by rbsremodeling

3 or 4 inch schedule 40 pvc pipe

You know, I have never tried that, but, that might just do the trick!!

I have heard that their exists a thin walled rigid plastic pipe but have never been able to find it.

Do you think plastic would be superior to galvanized??

MALCO.New.York · 01-18-2009, 12:59 PM

Quote:

Originally Posted by jarvis design

You know, I have never tried that, but, that might just do the trick!!

I have heard that their exists a thin walled rigid plastic pipe but have never been able to find it.

Do you think plastic would be superior to galvanized??

Certainly a better seal and more durable. A bit trickier in "Aiming". But that is easily fixed with opposing 45 elbows or a Fernco Fitting. The Fernco will also reduce the transmitted vibration of the fan.

http://www.terrylove.com/forums/atta...1&d=1203472990

rbsremodeling · 01-18-2009, 01:03 PM

Quote:

Originally Posted by jarvis design

You know, I have never tried that, but, that might just do the trick!!

I have heard that their exists a thin walled rigid plastic pipe but have never been able to find it.

Do you think plastic would be superior to galvanized??

The Galvanize I would assume be more susceptible to moisture damage vs PVC. Just a guess though

tcleve4911 · 01-18-2009, 01:13 PM

We always vent our baths with schedule 20. It's much lighter that sch 40 and less expensive. They often use it as drain tile.

Its flared at one end so couplings are not needed for long lengths.

Homeboy Depot & Lowest carries it in the plumbing dept.

Use PVC glue & fittings for sch20 & you're ready to vent.
Just don't dump it in the soffits.......

rbsremodeling · 01-18-2009, 01:19 PM

Quote:

Originally Posted by tcleve4911

We always vent our baths with schedule 20. It's much lighter that sch 40 and less expensive. They often use it as drain tile.

Its flared at one end so couplings are not needed for long lengths.

Homeboy Depot & Lowest carries it in the plumbing dept.

Use PVC glue & fittings for sch20 & you're ready to vent.
Just don't dump it in the soffits.......

I am afraid to use the sch 20 around here I would be afraid that flying debris would tear it up. lots of trees and stuff around the house we remodel.

I forgot we put angle on it with a screen to keep rain, trash and rodents out of it.

tcleve4911 · 01-18-2009, 01:21 PM

Quote:

Originally Posted by rbsremodeling

I am afraid to use the sch 20 around here I would be afraid that flying debris would tear it up. lots of trees and stuff around the house we remodel.

I forgot we put angle on it with a screen to keep rain, trash and rodents out of it.

I thought we were talking about venting a bath?

That would be interior venting, no?

tom m · 01-18-2009, 01:26 PM

I do like tcleve4911. Schedule 40 is heavy Rsb what does flying debris have to do with an internal bath vent?

rbsremodeling · 01-18-2009, 01:29 PM

Ok maybe I am the retard.

I thought the original op was talking about venting an exhaust fan to the exterior of an house

neolitic · 01-18-2009, 01:30 PM

Quote:

Originally Posted by rbsremodeling

I am afraid to use the sch 20 around here I would be afraid that flying debris would tear it up. lots of trees and stuff around the house we remodel.

I forgot we put angle on it with a screen to keep rain, trash and rodents out of it.

Geeze, I hate attics,
but yours sound down right
dangerous!

rbsremodeling · 01-18-2009, 01:34 PM

Quote:

Originally Posted by neolitic

Geeze, I hate attics,
but yours sound down right
dangerous!

If you ever saw a DC rat you'd be very, very afraid.

jarvis design · 01-18-2009, 03:03 PM

Quote:

Originally Posted by MALCO.New.York

Certainly a better seal and more durable. A bit trickier in "Aiming". But that is easily fixed with opposing 45 elbows or a Fernco Fitting. The Fernco will also reduce the transmitted vibration of the fan.

http://www.terrylove.com/forums/atta...1&d=1203472990

The Fernco is a great idea...wishing I thought of that myself!!

TTR · 01-18-2009, 03:10 PM

We put an expander from 4" to 6" right on the fan then run insulated flexible line until we reduce back down from 6" to 4" at the termination fitting. By increasing the diameter of the vent pipe right after the fan the restriction is reduced and we can get 100% of the rated CFM every time and it installs quickly. The fan runs quieter and is line is insulated for unconditioned spaces.

MALCO.New.York · 01-18-2009, 03:40 PM

Quote:

Originally Posted by jarvis design

The Fernco is a great idea...wishing I thought of that myself!!

They make 'em longer and more flexible than what I pictured. They are QUITE versatile!

MALCO.New.York · 01-18-2009, 03:44 PM

Quote:

Originally Posted by TTR

We put an expander from 4" to 6" right on the fan then run insulated flexible line until we reduce back down from 6" to 4" at the termination fitting. By increasing the diameter of the vent pipe right after the fan the restriction is reduced and we can get 100% of the rated CFM every time and it installs quickly. The fan runs quieter and is line is insulated for unconditioned spaces.

Is it not the smallest orifice in a "flow system" that determines the flow rate and pressure?

It is my belief that the six inch pipe in no way helps in actual CFM's once the termination is reduce back to 4".

If I am incorrect, please re-educate me.

Mike Finley · 01-18-2009, 03:48 PM

Quote:

Originally Posted by tcleve4911

We always vent our baths with schedule 20. It's much lighter that sch 40 and less expensive. They often use it as drain tile.

Its flared at one end so couplings are not needed for long lengths.

Homeboy Depot & Lowest carries it in the plumbing dept.

Use PVC glue & fittings for sch20 & you're ready to vent.
Just don't dump it in the soffits.......

Now I thought we were the only geniuses that had figure that out!

Actually I'm glad to see others doing that, to be honest I wasn't sure how code approved that was over the standard sheetmetal ducting. It always seemed like the more logical choice to me but I figured there was probably a tiny likelyhood it might run into some code issues.

We've always found it way easier to work with, with the one exception of sometimes it's tricky to get 8 or 10 footers into the attic!

TTR · 01-18-2009, 04:26 PM

Quote:

Originally Posted by MALCO.New.York

Is it not the smallest orifice in a "flow system" that determines the flow rate and pressure?

It is my belief that the six inch pipe in no way helps in actual CFM's once the termination is reduce back to 4".

If I am incorrect, please re-educate me.

We are typically retrofitting an existing installation and our job is tested by a 3rd party with a flow hood, so we have to get it right the 1st time. Each inch you increase the size of the pipe the restriction is reduced by 50%.

Each 90 or 45 degree angle introduces extra restriction on the line and makes the fan less efficient. 4" flexible line is the worst for restriction, 2 bends and the rated CFM can be cut by 60% even in short 2' runs. By bumping up the line size 2" the fan doesn't see any restriction in the 6" line even though it is the flexible insulated line. You can curl the 6" line 6 times around and still get 100% rated capacity. Not that we do this but it demonstrates how big a difference the line size can make.

Sure it would be even better to have a 6" termination but that is over kill, and usually we are using an already installed termination. The type of termination also makes a difference in the actual rating of the fan installed, if it a high restriction termination or broken we replace it.

Also if you can pipe the fan duct from the ceiling down a wall through the floor and out the wall you will eliminate a draft. I think it's a min of 3' drop to stop cold air working back in the winter.