Pitot tubes

[heatingman]

If I was to order a pitot tube, as a service guy, what length should I get to cover most typical applications?


Sent from my iPhone using Tapatalk

[WAYNE3298]

The 20 and 36 inch will do most of what you will need. The 36 inch will do anything the 20 inch will do if you can physically use it in the space. For TAB work the 20 inch will do almost everything if you don't mind double drilling holes in ducts larger than 24 inch. Having two tubes is far better but you can get by with one.

[icy78]

I have both but mostly use the 24.

[icy78]

@WAYNE3298 trying to send you a PM. It won't go thru. Could you check the TAB area and give me some wisdom on the Q fan question? MUCH appreciated!

[hvacker]

What type static pressure do you want to measure? Are you wanting to measure TESP or do you want to traverse a duct?
Do you run resi or commercial?

[heatingman]

What type static pressure do you want to measure? Are you wanting to measure TESP or do you want to traverse a duct?
Do you run resi or commercial?

For traverse. I normally use hot wire anemometers, but I want a pitot to confirm accuracy and as a simple back up.

I do commercial


Sent from my iPhone using Tapatalk

[icy78]

You use that Fieldpiece sta2 if I remember correctly. I bought that partly on your recommendation and have really liked that tool. The I did have trouble once with some readings that I regarded as suspicious, and it turned out that some duct lining fibers had lodged onto the thermocouple.

[heatingman]

You use that Fieldpiece sta2 if I remember correctly. I bought that partly on your recommendation and have really liked that tool. The I did have trouble once with some readings that I regarded as suspicious, and it turned out that some duct lining fibers had lodged onto the thermocouple.

Yes, thats my hot wire. I like it, and think it works well. But its harder to do the point type traverse and be repeatable. I was talking to an old timer the other day and he said he would put tape on the pitot to mark the sample points for repeatable readings. So, now I want one. Actually just ordered a 24" pitot from Dwyer.

Before that I used the "poor-mans pitot" when I wanted to get a feel for what was happening.

1/4" copper tube with a 90 bent on it to point into the airflow attached to positive port and a static probe on the negative. But, I am starting to do alot more airflow work, so its time to get a legit pitot.


Sent from my iPhone using Tapatalk

[vargimike]

Why do they cost so much. Or am i looking in the wrong places.

[heatingman]

Anyrhing TSI or Alnor is super expensive. Look up one by Dwyer, they're quite a bit cheaper.

But there a stainless precisely machines tool.


Sent from my iPhone using Tapatalk

[icy78]

The pitots are marked with ruler type markings etched into the stainless. I use a sharpy to mark the insertion points. Wipes off easily when finished with that traverse.

[Push It]

Our Shortridge kit has a airfoil tub for velocity readings also. Can anyone tell me when this would be better over the pitot tube?

[WAYNE3298]

You also probably got a velocity grid with the kit. I wouldn't use the vel-grid or airfoil unless there was no other choice. If you do be sure to read and follow the manual.

[Push It]

You also probably got a velocity grid with the kit. I wouldn't use the vel-grid or airfoil unless there was no other choice. If you do be sure to read and follow the manual.

Yes we have the velgrid. I have used it before to test fume hoods, economizers, etc.

[icy78]

How do you do kitchen hoods WAYNE.? Velgrid the entire hood or just the filters, or both, and average them?

Sent from my SM-G930V using Tapatalk

[WAYNE3298]

About the only way you can do a kitchen hood exhaust is at the filters with the vel-grid. The earlier Shortridge manuals gave a multiplier of 1.2 for vel-grid exhaust reading at the filters. At least one hood manufacturer complained that the multiplier was incorrect so Shortridge rescinded the multiplier. As you know very seldom can you traverse the kitchen hood exhaust duct but I have had that opportunity on 4 occasions. In comparing the vel-grid readings to the traverse on all four times the 1.2 multiplier was on the money. All four hoods were Captiveaire.
Fume hood certification testing includes tracer gas testing, airflow measurement and requires a video of the test. Hoods are not certified to pass or fail which in my opinion is a cop out. In my experience nobody wants to take any responsibility for whether a fume hood will perform as required, not even the manufacturer. The way I handled that on new installs was to inform all parties that I would traverse the duct and calculate the face velocity of the sash but would not do a certified test of the hood. That was to assure the hood was ready for a certified test. My opinion is not a popular one but it is what I sincerely believe.
Ernie Shortridge was alive when I got my first Shortridge kit. I called him and ask him about the vel-grid and he said it was designed to read airflow on the inlet side of AHU filters and for any other use had to have the correction multiplier. The worst place I tried to use it was the outlet side of a cooling coil. It was 40% high.

[GoCougs]

The pitots are marked with ruler type markings etched into the stainless. I use a sharpy to mark the insertion points. Wipes off easily when finished with that traverse.

Icy when do you choose a pitot over a hot wire? I know you've mentioned the FP STA2 in other threads so I figured you've had your share of experience with both.


Sent from my iPhone using Tapatalk

[icy78]

Icy when do you choose a pitot over a hot wire? I know you've mentioned the FP STA2 in other threads so I figured you've had your share of experience with both.


Sent from my iPhone using Tapatalk

Usually I use the hotwire when I'm interested what the velocity is. Meaning that I may know that I need 1500fpm in that duct. Am I close to it? Sometimes I only drill a couple holes and move the stick around a lot to get an average, albeit not so accurate. But if I'm looking for 1500 and am seeing 1100 for example then I am stopping and checking why. If I need an accurate reading on higher cfm for troubleshooting, then pitot tube.
If I have to do some balancing for our company, then I use pitot, hood, and hotwire. Hotwire is nice in the small ducts.
Also the vel-grid. I did not know that about a 1.2 multiplier.

When I did some balancing along time ago I remember standing on a 6ft stepladder inside 20 x 20 ft concrete duct, measuring velocity with a vel-grid on 20 x 20ft charcoal filters. That was kind of cool. Now that Wayne mentions that 1.2 multiplier, I wonder how far off we were on our readings. We read on the inlet side of the filters.

Sent from my SM-G930V using Tapatalk