Some local codes may preclude any vertical use of flexible air duct. Where it is allowed, ADC guidelines say that factory-made flex air ducts may not be used for vertical risers in air duct systems serving more than two stories. Vertically installed ducts also should be stabilized by support straps every 6 feet.
What are the three types of ducts?
There are three main types of ducting used within domestic ventilation systems: rigid ducting, semi-rigid ducting and flexible ducting.
How do you design ductwork?
6 Tips for Good Ductwork Design
Choose the best location for HVAC equipment and ducts. ...
A detailed load calculation. ...
Consider your equipment type and supporting systems. ...
Use the right materials, fittings and supports. ...
Choose the right duct size and layout. ...
Ensure proper ductwork sealing.
What size duct is needed for 1200 CFM?
The higher the cubic feet per minute, the larger the duct you'll need. At 600 CFM, the minimum duct size is 6”. At 900 CFM, the sheet metal ductwork fabrication minimum duct size is 8”. Finally, at 1200 CFM and above, consider a 10” diameter duct or larger.
Does reducing duct size increase pressure?
If your ducts are too small to accommodate the air flowing through them, the pressure increases and backs up in the system. This causes resistance for the blower fan, reducing your HVAC system's efficiency and longevity.
How many CFM is a 2.5 ton unit?
For instance a 2.5 ton system (Approximately 400 CFM per ton) would require (2) 14” flexible return ducts or (1) very short flexible 18” duct to move the 1000 CFM required by the 2.5 ton system.
What is semi-rigid duct made of?
The product is referred to as radial semi-rigid ducting, radial ducting, or occasionally just semi-rigid ducting. The material is made from high density polyethylene with a ribbed, flexible exterior and a smooth interior.