Table of Contents
- 1 What is the difference between the return and supply sides of a duct system?
- 2 Why are the return ducts slightly smaller than the supply ducts?
- 3 What is return air duct?
- 4 How do return air ducts work?
- 5 What is the air velocity in a duct?
- 6 Why is velocity important in ductwork?
- 7 Does air velocity affect HVAC ductwork?
- 8 What is duct velocity and why is it important?
What is the difference between the return and supply sides of a duct system?
The supply vents in your home blow conditioned air out into your rooms. This air travels from your heating and cooling system, through your ductwork and out of the supply vents. The return vents in your home suck the air from your rooms into your return ducts and back to your heating and cooling system.
Why are the return ducts slightly smaller than the supply ducts?
Yes, return ducts are usually larger than supply ducts to ensure that air within the home is balanced. There are generally more supply vents in the system creating the need for return vents to be larger. Ensuring that there is sufficient air supplied and returned is critical to maintaining an ambient environment.
How can air duct velocity be reduced?
As duct size increases, air velocity decreases, and vice versa. So we can increase the velocity of air in a duct by making the ducts smaller and we can reduce the velocity by making the ducts bigger.
What are some possible causes of low inadequate air velocity in an air duct?
Five Common Causes of Low Airflow in a Home
- Dirty Furnace Filters or Excessively Efficient Furnace Filters. This is an example of friction.
- Crushed, Blocked, Improperly Installed or Disconnected Duct Runs.
- Duct Leakage (Including Home Leakage)
- Not Enough Return Air Vents.
- Undersized Vents or Oversized Ductwork.
What is return air duct?
Return air ducts balance airflow in your HVAC system — The primary role of return ducts is to bring air that has been warmed or cooled back to your furnace or air conditioner. This air is returned so that it can be heated or cooled again, filtered of particulates and contaminants, and redistributed inside your home.
How do return air ducts work?
An HVAC system is basically a recirculating pump that works by heating or cooling air and then pumping it into a home. As conditioned air is pushed in, the air already in the home needs a place to escape. Return air vents serve this purpose by helping to pull in the air and putting it back into the system.
How much bigger should return duct be?
With a return and supply in each room it’s important for them to be of an equivalent size so that the room is not over or under pressured. For homes that have one or two main return ducts located in a hall or a great room, those returns should be equal in size to all the supplies throughout the home.
What size should a return air duct be?
The duct for this system must be sized by using 6 square inches of clear duct area for each 1000 BTU of cooling. Each ton of cooling contains 12,000 BTU. Multiply the tonnage, 3.5, by the total BTU per ton and this will give you the total BTU rating.
What is the air velocity in a duct?
Air velocity (distance traveled per unit of time) is most often expressed in feet per minute (FPM). Multiplying air velocity by the area of a duct allows you to determine the air volume flowing past a point in the duct per unit of time. Volume flow is generally measured in cubic feet per minute (CFM).
Why is velocity important in ductwork?
Flow velocity in air ducts should be kept within certain limits to avoid noise and unacceptable friction loss and energy consumption. Low velocity design is very important for the energy efficiency of the air distribution system. Doubling the duct diameter reduces the friction loss by factor 32.
Why is my air return not pulling air?
Return Air Duct Problem Causes The main reasons the HVAC system experiences issues with the return air ducts is because the duct is either blocked or leaking. The blockage could be inside the duct itself, or you may have just overlooked the placement of furniture or other personal items in front of the vent.
Why should air velocity in branch ducts be limited to 600 feet per minute quizlet?
Why should air velocity in branch ducts be limited to 600 feet per minute? To minimize air noise. The system cannot operate properly against excessive air restriction. Air is moving through a trunk duct that remains the same size through its entire length.
Does air velocity affect HVAC ductwork?
According to CIBSE Guide B – HVAC / 2005, clause 3.3.2, the duct air velocity is not a major factor in the constructional specifications of the ductwork. On the other hand the velocity of air flowing through a duct can be critical, particularly where it is necessary to limit noise levels and has a major impact on the pressure drop.
What is duct velocity and why is it important?
As service technicians, we are often expected to understand a bit about design to diagnose a problem fully. Duct velocity has many ramifications in a system, including: High air velocity at supply registers and return grilles resulting in air noise Low velocity in certain ducts resulting in unnecessary gains and losses
What are the effects of high and low air velocity?
High air velocity at supply registers and return grilles resulting in air noise Low velocity in certain ducts resulting in unnecessary gains and losses Low velocity at supply registers resulting in poor “throw” and, therefore, room temperature control
Where should my return-ducts be located?
If the supply ducts are in the floor, then the return air should be located up high. This pulls the air across your body. If the supply ducts are high or in the ceiling, then the return-air ducts or grills should be low on a wall. FREE Call From Tim Carter About Your Ducts – CLICK or TAP HERE. My House is Hot or Cold. Is This a Return-Duct Issue?