External Static Pressure

[spectrum]

Hello

I need help in the following

1- A rule of thumb in calculating the external static pressure for supply and return air ducts

2- Web sites that have a detailed but easy to apply and user friendly methods in calculating external static pressure

I have tried the methods in ASHRAE and SMACNA and find then very lengthy, had to make too many assumptions, and hard to apply.

Thank you in advance

 

[timr]

You need to provide more information. What type of application, ie, residence, institutional, commercial, anticipated velocity(if known), etc. There are rules of thumb. Just keep in mind rules of thumb are conservative, so an estimated static using rules of thumb should be higher than actual, meaning equipment will probably be oversized. timr

 

[spectrum]

Hello

the application is commercial building, the velocity is 1000 FPM, 1100 FPM, 1200 FPM.

By approximatly how much is it would be oversized?

 

[svanels]

The practical limits for air velocity on humans are
between 1.5 meter/min and 10 meter /min
or 4.9 fpm -- 32.8 fpm. Steven van Els
SAvanEls@cq-link.sr

 

[kailu]

Approximately, in a commercial building, assume 0.1"/100ft. for the duct length entire. Then assume another 0.5" of the AHU PD. If the AHU has apecial filters then add the PD as per filters manufacturers. In a one floor office with supply and return ducting and diffusers I would estimate approximate 1.5" as the external static pressure. This needs to be checked later exactly as it could oversize the motor.

Hope the info was useful

 

[Rockhead]

I also have a similar question regarding "External Static Pressure".

When viewing BLOWER DATA info, on for example, Trane XV80 gas furnace, External Static Pressure is always a factor on the chart, and is a fairly important one at that I'm sure.

Where and at what point exactly to you insert probe in duct? Also, do you insert low probe in R/A duct at the same time as high probe in S/A duct? Is that .45 your ESP that you are seeing on you magnahelic guage?
This exact manner in wich this measurment is performed has always been a big "?" for me, as it seems everybody has a differing view as to how it is correctly performed.

PLEASE HELP! Thanks, Rockhead

 

[Rockhead]

Rockhead, Feb 10, 2001
I also have a similar question regarding "External Static Pressure".

When viewing BLOWER DATA info, on for example, Trane XV80 gas furnace, External Static Pressure is always a factor on the chart, and is a fairly important one at that I'm sure.

Where and at what point exactly to you insert probe in duct? Also, do you insert low probe in R/A duct at the same time as high probe in S/A duct? Is that .45 your ESP that you are seeing on you magnahelic guage?
This exact manner in wich this measurment is performed has always been a big "?" for me, as it seems everybody has a differing view as to how it is correctly performed.

PLEASE HELP! Thanks, Rockhead