{"id":7463,"date":"2022-02-18T17:20:28","date_gmt":"2022-02-18T09:20:28","guid":{"rendered":"https:\/\/aircondlounge.com\/?p=7463"},"modified":"2024-03-26T12:07:27","modified_gmt":"2024-03-26T04:07:27","slug":"hvac-diffuser-sizing-guide-cfm-chart-selection","status":"publish","type":"post","link":"https:\/\/aircondlounge.com\/hvac-diffuser-sizing-guide-cfm-chart-selection\/","title":{"rendered":"HVAC Diffuser Sizing Guide: CFM Chart & Selection"},"content":{"rendered":"\n
Supply air diffusers are critical to HVAC air distribution system. Inappropriate supply air diffusers can cause the entire HVAC system to perform poorly. So, how do you size and select a supply air diffuser?<\/p>\n\n\n\n
Generally, the size of HVAC diffusers should be based on an airflow of around 250 CFM and a noise level of below NC30. 2 ft length by 2 ft width and 8 inches inlet diameter is the most common size for a 4-way ceiling diffuser. <\/strong><\/p>\n\n\n\n Unlike return air grilles, the size of supply air diffusers is not determined by a formula. Instead, we need to go through a process to find the most suitable supply air diffusers.<\/p>\n\n\n\n Since 4-way diffusers and linear diffusers are the two most common types of supply air diffusers in HVAC, I’ll be using both of them as examples in this guide. If you want to see what other diffuser types available, check out my post about the 6 different types of supply air diffusers.<\/a>.<\/p>\n\n\n\n Different sizes of HVAC diffusers can be used for the same airflow depending on the diffuser type. To give you a quick solution, below is the common diffuser sizes and their corresponded airflow.<\/p>\n\n\n\n Before we can select the supply air diffuser, there are two things we need to size first; a) physical dimension and b) neck size.<\/p>\n\n\n\n Physical dimension is the length, width and height of a supply air diffuser. Meanwhile, the neck size of a supply diffuser is the size of the connection between the diffuser and the supply duct.<\/p>\n\n\n\n The physical dimension of 4-way diffusers and linear diffusers is very different. At the same time, their sizing process is also quite different.<\/p>\n\n\n\nHVAC Diffuser CFM Chart<\/h2>\n\n\n\n
Airflow<\/th> Diffuser Size<\/th> Neck Size<\/th><\/tr><\/thead> 150 CFM<\/td> 2 ft x 2 ft <\/td> \u00d88″<\/td><\/tr> 200 CFM<\/td> 2 ft x 2 ft <\/td> \u00d88″<\/td><\/tr> 250 CFM<\/td> 2 ft x 2 ft<\/td> \u00d810″<\/td><\/tr> 300 CFM<\/td> 2 ft x 2 ft<\/td> \u00d810″<\/td><\/tr> 350 CFM<\/td> 2 ft x 2 ft<\/td> \u00d812″<\/td><\/tr> 400 CFM<\/td> 2 ft x 2 ft<\/td> \u00d812″<\/td><\/tr> 450 CFM<\/td> 2 ft x 2 ft<\/td> \u00d814″<\/td><\/tr> 500 CFM<\/td> 2 ft x 2 ft<\/td> \u00d814″<\/td><\/tr><\/tbody><\/table> Airflow<\/th> Diffuser Size<\/th> Neck Size<\/th><\/tr><\/thead> 50 CFM<\/td> 1-slot, 2 ft<\/td> \u00d86″<\/td><\/tr> 100 CFM<\/td> 2-slot, 2 ft<\/td> \u00d88″<\/td><\/tr> 150 CFM<\/td> 2-slot, 4 ft<\/td> \u00d88″<\/td><\/tr> 200 CFM<\/td> 2-slot, 4 ft<\/td> \u00d810″<\/td><\/tr> 250 CFM<\/td> 3-slot, 4 ft<\/td> \u00d88″<\/td><\/tr> 300 CFM<\/td> 3-slot, 4 ft<\/td> \u00d810″<\/td><\/tr> 350 CFM<\/td> 4-slot, 4 ft<\/td> \u00d810″<\/td><\/tr> 400 CFM<\/td> 4-slot, 4 ft<\/td> \u00d812″<\/td><\/tr><\/tbody><\/table> How to Size a Supply Air Diffuser?<\/h2>\n\n\n\n
A) Physical Dimension<\/h3>\n\n\n\n
4-Way Directional Ceiling Diffuser<\/h4>\n\n\n