Book on static pressure testing.

[leslie cook]

I am looking for a book on static pressure testing. I am confused. Some information I see has you putting the probes in the supply plenum and the return air plenum. Some have them before and after the blower.

[WAYNE3298]

It depends on what you are looking for. Having said that most of the time you are looking for the blower differential pressure and those readings are taken before and after the blower. The purpose for the readings is to determine if the blower actual total static pressure is in line with the blower design. You get a rough CFM reading that way.

[ch4man]

I dont have it handy, but if you ask rundawg here nicely, he'll send you a very nice pdf on it I would think...

[crazzycajun]

Have you seen Jim tutorial

[WAYNE3298]

The biggest problem with static pressure is getting an accurate measurement. Think about the results of the readings because swirling airflow can give wild readings. On a resi unit to get the fan discharge static you are measuring in the blast area of the fan so weigh the results carefully.

[stanbyyourword]

Titus have some great stuff on youtube

[pecmsg]

*

[leslie cook]

Thanks to everyone

[Artrose]

What kind of pressure testing do you need to perform? Air? Water? Static pressure? Total pressure? Velocity pressure? Differential pressure? Other?

Let's scratch the surface.......

In a piece of ductwork, Static pressure Sp is the bursting pressure inside the duct. Using your magnehelic, your (+ or HI) probe is inserted perpendicular (90deg) to the airflow, and referenced to ambient. Total pressure Tp is the ram air pressure that is exerted on your (+ or HI) probe inserted into the duct with the open end facing directly into the oncoming airflow, referenced to ambient. Velocity pressure Vp = Tp + Sp Vp is used in duct traverse calculations ...abreviated...[ Sq rt of Vp times 4005 times duct area in Sq Ft equals CFM] to determine airflow CFM (cubic feet per minute) in an air duct.

Differential pressure is the difference in static pressure across something in the airstream, a fan, coil, filters, or any number of other items found in air duct systems. Differential pressure readings are handy to establish if a system has a restriction, such as a dirty coil, closed fire damper, dirty filters, or any number of other restrictions to design airflow. Note: Many residential techs do this...... Don't use fan differential pressures, and a units differential pressure/cfm chart to determine cfm. It is not a good pratice if you need accurate results. Might work fine in a laboratory, but not so good in the field, and it doesn't cut it in the commercial/industrial world.

All of these pressure readings should be taken in areas of the ductwork that is relatively free from as much turbulence as possible. Example: for a traverse, one rule of thumb is that readings should be taken in a straight area of the ductwork, 3 to 4 duct diameters downstream from any transition, elbow, damper, tap, or any other source of turbulence.
One other note: Remember, Air and Water are both fluids, and have several very similar behaviours. If you can grasp how either of them work, at least to some degree, you are on your way.