Showing Posts From
Airflow
Duct Size Chart: How to Match Duct Size to CFM
A round duct size chart by CFM, what a ductulator actually does, the friction-rate and velocity rules behind it, how to convert round to rectangular, and how to size supply vs return ducts.
Return Air Duct Sizing: How to Size the Return Side
How to size return air ducts: why returns must match supply airflow, a return duct size chart by CFM, single vs multiple returns, filter grille sizing, and the static-pressure problems undersizing causes.
Fan Laws Explained: How Blower Speed Affects Airflow
The three fan affinity laws relate blower speed to airflow, static pressure, and power. Why a 10% speed increase costs 33% more power, with worked examples.
What Is CFM and How to Calculate It
CFM is the volume of air your HVAC system moves per minute. What it means, the 400 CFM per ton rule, the formula to size airflow per room, and how to measure it.
HVAC Duct Sizing: Manual D vs Rules of Thumb
How to size HVAC ducts using the Manual D friction rate method and simplified rules of thumb, with duct velocity limits and why wrong sizing causes comfort problems.