When checking total system static...

[hvaclover]

..does anybody use only the 1/4" id metal sensing tubes your manometer kit came with?

[mark beiser]

If you are talking about the straight piece of tube that used to come with a lot of water manometers and magnahelic gauges, no, they are useless for static pressure readings.

If you are talking about actual static pressure tips, than yes, I use those, and occasionally my telescoping pitot tube when I need to "feel around" in a duct for a good static pressure reading, or do a velocity pressure traverse.

[y7turbo]

http://productimages.grainger.com/is/image/Grainger/1W401_AS01?$productdetail$


http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=static+pressure+tip&op=search&Ntt=static+pressure+tip&N=0&sst=subset

[hvaclover]

YEP I get it.

Saw the video too.

Got a new EM 201 dig manometer and investing in a megnehelic (it's inexpensive insurance).

Got two static probes on order too...still got a lot to learn since I was taught air-flow old school.

[hvaclover]

anybody got any advice for an old dog learning new tricks?

[mgenius33]

YEP I get it.

Saw the video too.

Got a new EM 201 dig manometer and investing in a megnehelic (it's inexpensive insurance).

Got two static probes on order too...still got a lot to learn since I was taught air-flow old school.

Henri Pitot's test instrument has been around for almost 3 centuries. That's about as old school as it gets.
A simple static tube will simply read pressure perpendicular to the flow. Which is the walls of the duct of a straight section of duct.
This opinion is probably not popular, but I don't waste my time with static tips. Pitot's are useful though.
For example, we trust highly accurate combustion analyzers to read stack pressure, but they are not bent at a 90* angle with a pointed tip.

[hvaclover]

thanks for that. had no idea the pitot tube was that old.

Your opinion is valued and one has to walk before he can run....duct system testing is something that does not become an acquired skill over night.

[DeHeatify]

I hear that! I am only 2 yrs in the biz but after troubleshooting airflow issues in my sons room I have so far invested in a static pressure tip a testo 410-1 velocometer and a digital sling pyscrometer.. Already have a dual port manometer and and started the long reading journey to try to understand this area of hvac better. I wold really like to get to a point that I can benefit my customers and troubleshoot airflow issues with ease..
Finding the info is the tricky part. I have also made a 12 x 12" square box to use as a flow hood but am trying to research the proper operation of one.

Everytime I learn more... I learn that I know less!!!

Sent from my BlackBerry 8530 using Tapatalk

[mark beiser]

This opinion is probably not popular, but I don't waste my time with static tips. Pitot's are useful though.
For example, we trust highly accurate combustion analyzers to read stack pressure, but they are not bent at a 90* angle with a pointed tip.

There isn't much in the way of velocity pressure to interfere with a static pressure reading in the typical combustion vent system...;)

[ACFIXR]

anybody got any advice for an old dog learning new tricks?

Secure the magnets on your probes with some epoxy, they tend to disappear.

Always have a 1/4" drill bit thats handy.

Whatever your brand that you typically work on make a temporary door switch

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/019-1.jpg

and temporary hi limt cover so you can insert your probes.

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/Blank_Off_Plate-1.jpg

If you bought the low range mag you won't be able to see the problem system's because your mag will be pegged.

[mark beiser]

Whatever your brand that you typically work on make a temporary door switch

Why?

Static pressure readings with the blower door off are useless...

[mgenius33]

There isn't much in the way of velocity pressure to interfere with a static pressure reading in the typical combustion vent system...;)

That's my point, you're not reading/calculating velocity pressure with a static tip. I don't see a static probe being any more useful in calculating airflow than taking a reading flush with the inner wall of the duct, perpendicular to the flow. Most static probes used are only 3 ", so laminar flow isn't really a factor. Also, static pressure is the force exerted on the walls of the ducting. So, what better place to take the reading, than on the wall of the duct.
Seeing as the 2 methods will only yield a couple hundredth of an inch wc difference, is it really going to make a difference in using a cfm calculation method that is marginal at best?

[ACFIXR]

Why?

Static pressure readings with the blower door off are useless...

Removing a blower door can tell me more about a system in a few seconds than 10 minutes of probe insertions.

[hvaclover]

Removing a blower door can tell me more about a system in a few seconds than 10 minutes of probe insertions.

would you please elaborate?

[hurtinhvac]

I have the EM201 as well and the static pressure tips - looking for advice and experiences etc. as well...

[hvaclover]

Removing a blower door can tell me more about a system in a few seconds than 10 minutes of probe insertions.

Whaddaminnit...are you talking about removing the blower door and allowing it to pull back to see with how much force it sucked back?...that was one of the old school techniques I was referring to.

[mgenius33]

I have the EM201 as well and the static pressure tips - looking for advice and experiences etc. as well...

What are you trying to learn?
Your set up will prove to be useful for detecting airflow restrictions.

[mgenius33]

Whaddaminnit...are you talking about removing the blower door and allowing it to pull back to see with how much force it sucked back?...that was one of the old school techniques I was referring to.

Yes, the proven method. Use a luggage scale, by attaching it to the blower door. Measure the amount of force require to pull the door open. Take the inverse of the cubed root of that number and multiply by 1000. The answer is your CFM. Lol:grin2:
The scale can also be used as a backup refer scale.

[ACFIXR]

Whaddaminnit...are you talking about removing the blower door and allowing it to pull back to see with how much force it sucked back?...that was one of the old school techniques I was referring to.

Yes, it becomes pretty obvious when the doors are off what your dealing with. Through the years what I have typically found to be the majority of installed systems are undersized filter racks and/or small return duct.Another is a blocked evap coil from lint. Here's a reading from a blocked evap with the "DOOR ON":grin2:

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/Fluke9221.jpg

[hvaclover]

EEEEEE HAAAAHHHHH....little high there ROTFLMAO!

[hvaclover]

Yes, it becomes pretty obvious when the doors are off what your dealing with. Through the years what I have typically found to be the majority of installed systems are undersized filter racks and/or small return duct.Another is a blocked evap coil from lint. Here's a reading from a blocked evap with the "DOOR ON":grin2:

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/Fluke9221.jpg

Nice meter. Don't believe I have ever seen it before.

Fluke 922?

What it set you back and what else does it do?

[mark beiser]

Yes, it becomes pretty obvious when the doors are off what your dealing with. Through the years what I have typically found to be the majority of installed systems are undersized filter racks and/or small return duct.Another is a blocked evap coil from lint.

Ok, I'm with you now.
Yes, tricks with removing the blower door are useful for quickly determining where the problem is in the system.
Not so much for checking the normal operation of the system.

[ACFIXR]

Nice meter. Don't believe I have ever seen it before.

Fluke 922?

What it set you back and what else does it do?

I don't recall the cost,it wasn't cheap but I'm a Fluke guy. I could do volume calcs with velocity readings from this thing but I usually cant find any straight duct :gah: so i use the pressure readings to match rpm's

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/rpms.jpg

to volumes so I can calculate and adjust cfm's.

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/Balancing.jpg

I do mostly light commercial package units with belt drives. So my work is relatively simple compared to residential testing and balancing. Most resi duct systems are designed and installed by ..........well..............I'll just leave it at that.

[hvaclover]

Silly question any way... all i had to do was Google it..does a lot of nice stuff.

Since all my test stuff is over ten years and I need to up-date, I am adding a lot of stuff to my list that wasn't available ten years back.

[mgenius33]

I don't recall the cost,it wasn't cheap but I'm a Fluke guy. I could do volume calcs with velocity readings from this thing but I usually cant find any straight duct :gah: so i use the pressure readings to match rpm's

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/rpms.jpg

to volumes so I can calculate and adjust cfm's.

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/Balancing.jpg

I do mostly light commercial package units with belt drives. So my work is relatively simple compared to residential testing and balancing. Most resi duct systems are designed and installed by ..........well..............I'll just leave it at that.

I'm interested in learning this method of cfm calculation. Could you elaborate on using a tachometer and manometer. Is a chart provided by the manufacturer?
I understand the static chart method, but how does the tachometer come into play? Are you just using the tachometer for ensuring ideal hp adjustment?

[mark beiser]

I'm interested in learning this method of cfm calculation. Could you elaborate on using a tachometer and manometer. Is a chart provided by the manufacturer?
I understand the static chart method, but how does the tachometer come into play? Are you just using the tachometer for ensuring ideal hp adjustment?

The blower performance charts for commercial belt drive equipment references HP or static pressure and RPM rather than static pressure and blower speed tap.

Airflow adjustments are made by adjusting the motor sheave, to change the RPM of the blower wheel, rather than changing speed taps.

[beenthere]

The units manual will list static at X RPM at X HP, equals X CFM.

[ACFIXR]

I'm interested in learning this method of cfm calculation. Could you elaborate on using a tachometer and manometer. Is a chart provided by the manufacturer?
I understand the static chart method, but how does the tachometer come into play? Are you just using the tachometer for ensuring ideal hp adjustment?


Here is how my manufacturer recommends checking volumes.

RPM and volume and pressure are closely related, has something to do with the fan laws


http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/HVAC_Tools/Fanlaws.png


which I can only understand with a magnahelic, tachometer and /or hood in my hands.:grin2:

[mgenius33]

Thanks, it's good to know alternatives. Nice that they give you bhp vs cfm charts.
Do you calculate the bhp when charts aren't available?
Off the top of my head, is it watts x pf x 746

[slctech]

Utilizing the laser tachometer, where are you guys affixing the reflective tape to get accurate rpm readings? I still have my old mans handheld tach which I just touch to the end of the blower shaft. Thinking of jumping to laser.

[mark beiser]

Thanks, it's good to know alternatives. Nice that they give you bhp vs cfm charts.
Do you calculate the bhp when charts aren't available?
Off the top of my head, is it watts x pf x 746

The tricky thing with downflow rooftop package units is getting good ESP readings when you can't really get to the supply and return ducts under the unit.:gah:
That is when a telescoping pitot tube comes in handy. :)
http://www.dwyer-inst.com/PDF_files/166T_IOM.pdf
Pricy though.

[hvaclover]

Well I have a couple ASP1 4" sensing tips on order...

Do you think I should get longer tips?
I don't think I am ready for a pitot tube yet.

[ACFIXR]

Utilizing the laser tachometer, where are you guys affixing the reflective tape to get accurate rpm readings? I still have my old mans handheld tach which I just touch to the end of the blower shaft. Thinking of jumping to laser.

All the new units I get already have the reflective tape on them, I guess from factory adjustments. On fan blades I just have to remember to divide by the number by the number of blades on the fan with this Extech tach because it's so sensitive. Back in the 80's I used to have a meter that I used to set the old style Hoffman head pressure controllers with a laser/light meter and It barely could pickup the reflected light from the tape much less the fan blades in full sun.Anybody remember doing that? :gah: