Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Register Calendar Latest Topics
 
 
 


Reply
  Author   Comment  
gbwillson

Avatar / Picture

Registered:
Posts: 2,126
Reply with quote  #1 
Hi Gang-

Below is a PDF about HVAC ducting. The part I was most interested in dealt with equivalent duct length or EL. A 1' straight pipe has an EL of 1. Some elbows and take-offs can have an EL of well over 100. That means a single connector has the air flow resistance of over 100' of straight pipe. You can use this to identify better choices for duct connections to keep the flow resistance as low as possible. 

Greg in MN[tongue]

Here is a page from the document:
pdf Duct Equivilent Length.pdf     

Here is a link to the entire document:
http://web.fscj.edu/Mark.Bowman/handouts/ACCA%20Friction%20Rate%20Reference%20Chart.pdf





solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #2 
Thanks Greg for ruining my day.  I have far to many 4Qs which are the same as 50 feet compare to something that seems to be the same a 4R which is 20 the equivalent to 20 feet.

Good info though.....
gbwillson

Avatar / Picture

Registered:
Posts: 2,126
Reply with quote  #3 
Dan-

My neighbor with the ZP has two 6' straight duct runs. Or at least they are straight until he has a 90˚ adapter at each end with an equivalent length of 80' at each end. Even with identical fans, and about 42' of duct runs I still get better flow than he does. He's running hotter than he should and is going to try a fan at each end and see if that helps.

Greg
netttech

Registered:
Posts: 720
Reply with quote  #4 
Good Info GB! [smile]

Jeff
Central IL
Solar air & water
gbwillson

Avatar / Picture

Registered:
Posts: 2,126
Reply with quote  #5 
Hi Gang-

Over the weekend I put up my ZeroPass heater. I'm quite limited in where I place my heaters, so I have to deal with duct runs much longer than I would like, so I was looking for any way to improve flow. This year the only thing I changed was the adapter that connected my ducts to the fan. And man...what a change! 

I switched from an end boot to a straight boot and increased my flow by 24%!!!

End boot on the left, straight stack boot on the right
IMG_0887.jpg 

The numbers on the ducts are the MPH that the fan pushed through the adapter. The improvement was quite noticeable without my anemometer. The end boot has an EL that is over 10x that of the straight boot. I didn't get a chance to measure the improvement in flow through the ZP itself as the increased flow blew apart(pun intended) several connections. And by the time the repairs were completed, the sun had faded. So my suggestion to everyone is to reassess your ducts, specifically the adapters and elbows and see where you can make some easy and inexpensive changes. Keep in mind, that at higher, more efficient flow rates, any restrictions and/or bottlenecks only get worse.

Greg in MN[wave]

stmbtwle

Avatar / Picture

Registered:
Posts: 2,546
Reply with quote  #6 
Good to know, thanks!
__________________
Willie, Tampa Bay
longoria6111@gmail.com

Registered:
Posts: 12
Reply with quote  #7 
Plastic or metal better cheaper? 4 in new Guy thanks
gbwillson

Avatar / Picture

Registered:
Posts: 2,126
Reply with quote  #8 
Not sure what you mean? Are you wondering if solid metal ducts are better than plastic flex ducts? If so, yes, solid is better in most circumstances. Solid ducts have a smoother sides so air flows through them easier. But if you pull the flex duct very tight, you can get pretty smooth sides for better flow. But most people done or can't pull flex duct tight enough so it leaves ridges on the sides of the duct which increase flow resistance. Solid is more expensive, but I think if you have a strong, more efficient air flow, it is worth the extra money. In fact, many of us have removed the flex duct from the insulated sleeve and inserted a solid duct. This means you end up being both, adding to the expense. 

I would suggest for a first time builder to use flex duct, pull the duct as tight as possible to smooth the sides and if you are happy with the performance, leave it as is. But if you are moving a lot of CFM through your system and want better airflow, use the solid ducts with the insulated sleeves.

Greg in MN[wave]
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics