Static pressure testing

[Zippy4god]

Just wondering how many techs check static pressures on systems in the homes we are servicing.
How important is it?

[Air Movers]

I think its one of the most important things, you can have everything else correct but if your airflow and cfm's are not proper your systems not proper. That can be the biggest reason for fan motor problems, balancing and airflow problems, you have to have that right in order for everything else to be right. Good luck charging and servicing a unit properly with static pressure issues!!

[Trehak01]

I try to on any call I can just because I am trying to learn how to understand airflow and how it effects the system.

[mark beiser]

I agree with Air Movers, it is one of the most important things to check.
At the very least, it needs to be checked and documented when the equipment is first started up, or the first time you service a system you haven't been to before.
I also note the ESP, blower speed, CFM, supply static and return static on the equipment with a marker.
That way I have baseline readings to compare it to if I have to troubleshoot a problem later on.

Judging by the complete lack of test holes in literally every system I see, that hasn't been serviced by us before, the percentage of people in my area actually checking static pressures, or even getting the most basic evaporator entering air temperatures needed for correct charging, is very low.

[ferd1942]

I think it's a topic many contractors don't want to know about: They've always used 500 SF/Ton and 0.10"/100 feet and they've "never had a problem".

It's good to see people who think otherwise, may your tribe increase.

[mark beiser]

They've always used 500 SF/Ton and 0.10"/100 feet and they've "never had a problem".

Yeah, if you never actually test anything, of course you "never had a problem".

[dlove]

Just wondering how many techs check static pressures on systems in the homes we are servicing.
How important is it?

I would say on a routine maintenance inspection Never. And most of the time techs will not check SP across the evap. Over all if you have a steady customer its good to check and to keep records. yes SH, SC and pressures can tell you a lot but SP is good to know.

[hvacker]

Let me tell you why static tests aren't that important.
A fan curve is plotted from laboratory test data under ideal conditions with NO inlet restrictions.
Not every fan is tested. Similar fans have curves developed by interpreting
test data.
Sometimes they are useful as a design tool
They represent laboratory data and do not represent measurable performance under field conditions.
They can be useful in trying to get a probable performance of a fan type.
You cannot predict the CFM of a fan from lab data because it'd difficult to predict system effect.

This information was gleaned from T&B data of the Sheet Metal and Air Conditioning Industry.
I've always thought that too much emphasis has been placed recently on static testing to the point of replacing real T&B instrument testing.
On T&B reports, static tests were made to inform the engineer but the numbers that really matter are the actual real world performance measurments.

[Central NC Tech]

What are some of the tools you are using to check for proper static? digital versus mag
nehelic, etc..

[hvacker]

What are some of the tools you are using to check for proper static? digital versus mag
nehelic, etc..

I use an Alnor velometer with a static probe. Because I don't consider the TSP to be as important as actual air flow measurements almost any instrument such as a magnehelic or a manometer would be ok.
A lot of emphasis is placed on static measurements by the manufacturers of test equipment. Some make it sound like a one tool fits all and this is all you need. I doubt anyone with a T&B cert would agree with this.

[ch4man]

I use an Alnor velometer with a static probe. Because I don't consider the TSP to be as important as actual air flow measurements almost any instrument such as a magnehelic or a manometer would be ok. A lot of emphasis is placed on static measurements by the manufacturers of test equipment. Some make it sound like a one tool fits all and this is all you need. I doubt anyone with a T&B cert would agree with this.

will you please rephase your second sentence. its a little unclear. thank you very much.....

i am very much interested in air flow measurement and have also seen many inconsistances (sp) reguarding tesp vs capacity checks and also dipswitch settings vs. ecm motors/ cfm

[sabur2121]

I think static pressure is very important. I can understand why some guys use 0.10, but its not very good practice. If you add electric filters ect. then you static pressure will change. The best thing for techs to do is refer to the Manual D If are confused or have any questions.

[dlove]

Let me tell you why static tests aren't that important.
A fan curve is plotted from laboratory test data under ideal conditions with NO inlet restrictions.
Not every fan is tested. Similar fans have curves developed by interpreting
test data.
Sometimes they are useful as a design tool
They represent laboratory data and do not represent measurable performance under field conditions.
They can be useful in trying to get a probable performance of a fan type.
You cannot predict the CFM of a fan from lab data because it'd difficult to predict system effect.

This information was gleaned from T&B data of the Sheet Metal and Air Conditioning Industry.
I've always thought that too much emphasis has been placed recently on static testing to the point of replacing real T&B instrument testing.
On T&B reports, static tests were made to inform the engineer but the numbers that really matter are the actual real world performance measurments.

i agree with what you say in the most part. But when you come upon a system you never worked on, SP is good information to to have. Like whats the pressure drop across the coil or filters, whats the SP at the farthest point in the duct run

In a VAV system, using bypass dampers or VFDs or vortex dampers ect..SP becomes more important. Taking the time to understand pressures is another slice of the pie you shouldn't leave out.

when you go to a job the customer is not waiting there with the last T&B for you to read. Its nice to check a few spots with a electronic manometer. You may be surprised what you find.

[beenthere]

I use an Alnor velometer with a static probe. Because I don't consider the TSP to be as important as actual air flow measurements almost any instrument such as a magnehelic or a manometer would be ok.
A lot of emphasis is placed on static measurements by the manufacturers of test equipment. Some make it sound like a one tool fits all and this is all you need. I doubt anyone with a T&B cert would agree with this.

If you don't take a ESP/TESP reading. How do you know how much air the RTU/AH is moving. Not unusual for the supply and return to be moving different amounts of air due to duct leakage.

ESP/TESP readings will tell how much air the unit is moving. But not how much air is being delivered.

[hvacker]

If you don't take a ESP/TESP reading. How do you know how much air the RTU/AH is moving. Not unusual for the supply and return to be moving different amounts of air due to duct leakage.

ESP/TESP readings will tell how much air the unit is moving. But not how much air is being delivered.

For the reasons I listed in post #8 the numbers aren't consistently reliable Which is why the numbers regarding the amount of air being moved aren't reliable.
Again, these criticisms about static testing reliability in terms of real numbers I didn't make up. They are available in TAB publications. My only interest in pointing out possible misinterpretation of the numbers.
I include static tests in T&B reports, I just don't give them much weight.
Any tool is useful as long as you know it's limitations. As a quick method of troubleshooting these tests can have value but keep in mind operating conditions are usually different from design and sometimes by a considerable amount.

[hvacker]

will you please rephase your second sentence. its a little unclear. thank you very much.....

i am very much interested in air flow measurement and have also seen many inconsistances (sp) reguarding tesp vs capacity checks and also dipswitch settings vs. ecm motors/ cfm

Sure.
A lot of emphasis is placed on static measurements by the manufacturers of test equipment. Some make it sound like a one tool fits all and this is all you need. I doubt anyone with a T&B cert would agree with this.
I've seen advertisements on Youtube showing the methods for using a digital manometer for TESP tests w/o ever mentioning the shortcomings of the data charts and graphs. The fact that some data is interpolated from another fan is a little unsettling if I am relying on my numbers to be accurate.
It's the problem of comparing laboratory performance with real world numbers. Again, I think these tests are useful within their limitations.

[jrhicks]

Recently, Ive been learning more about static pressure. I serviced a Goodman gaspac with an external static pressure range between 0.1 to 0.5. Does this represent the total static pressure, or supply only?

[rundawg]

I serviced a Goodman gaspac with an external static pressure range between 0.1 to 0.5. Does this represent the total static pressure, or supply only?

Total.

One test probe in the supply duct, and one in the return duct, as near to the unit as possible.

Be sure to read blower performance chart notes for specific unit conditions (i.e.- wet or dry coil, with or without filter act...)

[jrhicks]

I appreciate it rundawg. According to my total number, Im within specs. My supply was bouncing from .05 to .10 and return from .20 to .25. Is that typical for return to read higher?

[rundawg]

I appreciate it rundawg. According to my total number, Im within specs. My supply was bouncing from .05 to .10 and return from .20 to .25. Is that typical for return to read higher?

I don't think you can call any of it typical, but undersized returns are very common.