This video shows you how to use a Testo 510i with the Testo Smart Probes App and a pitot tube to read duct velocity and CFM. Unlike a static pressure tip, a pitot tube has a hole. That hole accounts for velocity, and additional holes account for static pressure. You get velocity by taking the total pressure and subtracting the static pressure.
Velocity changes at different points of the duct. So, we must perform a duct traverse to read at various points of the duct and average out our readings. Alternatively, you could perform a timed average traverse where software takes readings as you're pulling the pitot tube through the duct. Pitot tubes must be inserted all the way into the duct for the most accurate measurements.
Pitot tubes connect to the Testo 510i with hoses. It is best to make sure that your hoses are 4-8 feet long. Connect the hoses to the static and total pressure ends appropriately. Then, connect the hoses to the Testo 510i ports on the positive and negative sides as appropriate.
When taking duct measurements, think about the duct's anatomy to set up the best possible testing conditions. For example, you'll want to try to stay away from transitions to limit turbulence. It is easy to make holes for a duct traverse in a round duct. Profile your duct in the Testo Smart Probes app and set your testing mode and parameters.
When you insert the pitot tube and are ready for testing, press the "play" button on the Testo Smart Probes App and pull the tube out slowly. In this case, Bryan pulls out the tube in about 13 seconds. After you've finished taking your measurements, the "stop" button on the app will give you your measurements. You can use your airflow and CFM measurements to calculate enthalpy and velocity.
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This video is a joint production of HVAC, our school comm, the HVAC school podcast in true tech tools, comm true tech tools, quality tools, essential support, hi, i'm brian, with the hvac school podcast in hvac, our school comm. I'm making this video today in conjunction with true tech tools, comm and what we're going to be talking about is the 5-10 i handheld wireless manometer. So the first thing that you'll notice about this is it's extremely small fits right in the hand very nicely. It's got a nice magnet, but it doesn't have a readout because it connects to your smart device, your smart phone or your iPad or whatever the case may be using bluetooth and what's nice about this, is it gives you the ability to do all the normal things That you do with a manometer reed gas pressure test pressure switches read static pressure, but in addition to that, you can actually use this to read airflow and it has a lot of pretty smart software in the app that allows you to do this more easily than Traditionally would be the case, and so today we're going to be using a pitot tube.

This is a pitot tube. This is not a static pressure. Tip static pressure tip is not open on the end. If you can see here, we have an opening at the end of this pitot tube and the static pressure tip doesn't have the l-shape.

It only has just the end, and the reason is is that on a static pressure tip, it comes at all of the static pressure comes in the sides, there's no tip, and it just comes at the end, and you read the static pressure in the case of A pitot tube, you have a total pressure port which is the end, and then you have the static pressure which is read through these little tiny holes on the side. Those are kind of hard to see is very small, and what happens is is that, by connecting the total pressure port to the positive side of your manometer and connecting the static pressure side to the negative side, this is a differential manometer. What it does is it takes the differential between the two and calculates your velocity pressure. So, what's coming in, the tip is not just velocity pressure, it has to be so it has to have the static pressure subtract it off, because static pressure is also affecting the tip.

So when you insert this into the duct - and let's say the air flow is coming this way what's coming, this tip is going to be velocity plus static pressure. Let's come what's affecting these little holes on the sides are just going to be static pressure so by subtracting the static pressure from the total pressure. We get the velocity pressure now. The challenge in making these types of readings is that we're tempted to take this reading.

Just at one point you know take this insert it into the duct. Take a reading. Well, velocity varies significantly based on where you take the reading in the duct. So if you take it on the sides or in the middle, that's going to significantly change and it will give you wildly different readings.

So the only way to do this properly is what's called a duct Traverse in an adduct Traverse. You have two options: either you read at various points throughout the duct and you do the math, you average it all out or you do what's called a time to average Traverse and that time the average means that you use software in most cases and that's what We're going to do today and it actually is measuring the entire time as you're pulling the pitot tube out of the doctor as you're moving it through the duct, and then it makes the calculation now. The most important thing when you're doing a traverse is you have to actually lay out the duct properly and on a rectangular duct. You take it on five different Traverse points in most cases and I'll share how to do that in a link.
But what I'm going to be doing today is just a round duct and in my home I actually have some spiral. Duct work. When I want to built the house, I always wanted to have spirals, so I have a couple sections of exposed spiral which make it easy to demonstrate this, especially since I only have a 12 inch pitot tube. So I can't use a duct with a diameter of over 12 inches, because when you do the Traverse, you have to traverse the entire depth of that duct when you do the time the average Traverse.

So that's what we're going to do there's a couple things. I need to tell you specifically about the measurements that I'm taking today, I'm using a short pitot tube, which is easy to handle and easy to demonstrate on a video, but again, generally speaking, a 12-inch pitot tube is not a really practical tool. It's not something! You're generally going to use a lot because pitot tubes are generally designed for higher velocity pressure. So if you have a commercial environment with high duct velocity, a pitot tube is a nice accurate way of doing that.

I'm reading this in a residential application, an 8-inch spiral duct, not generally what you would use a pitot tube for. You would generally probably choose an anemometer of some sort, hot wire anemometer or a vane anemometer inductive an anemometer to do this, but I'm demonstrating this tool. So I'm going to show you how to do the time Traverse. Also, a lot of people will take a pitot, tube and they'll insert it halfway into the duct so right in the center of the duct, it will take a single reading and they'll multiply it times.

0.9, a lot of people swear by that way of doing it, and it's not a bad way of doing it. If you have a really small duct, but it's still not quite as accurate, because you're not getting the full range of the duct inand, taking into account any changes from the velocity of the sides to the center, so we're not going to do that. You can do that actually, with the test of smart probes app. It allows you to take a single point reading and it will give you a readout, but that's not really what we're here to demonstrate today.
The other thing to mention is that the way that the way the dwyer recommends it is that you have eight and a half diameters passed so eight. So if you take the duct diameter multiplied that times eight and a half times you measure that past any transitions or changes in the duct. I do have a reducing transition, that's a little less than 68 inches. So it's an eight inch duct times.

Eight eight point five. So it's it's not I'm not exactly what they're looking for, but I did keep it as far away from the transition as I could, as I could get with, based on the way that it's laid out so anyway, I'm just letting you kind of know the reasons Why the readings that I'm going to take aren't going to be exactly within specification but will still be able to accurately demonstrate how to use it. But before we do anything else, I want to first show you how to connect up the pitot tube to the manometer. So I've got some long hoses, it's good to have decent length hoses to work with you don't want.

You know just a couple inches long in this case. These are about I'd, say, five feet long right in that range, and what I'm going to do is I'm going to connect these. This is actually a 5/16 pitot tube. So I have different hose sizes, but it really doesn't matter.

You obviously have to use the proper hose size for your for your pitot tube that you have and then you have to adapt it down to the smaller hose size for the actual manometer. But the manometer comes with the smaller hose size and in most cases when you buy your pitot tube, that's usually going to come with the larger size. So anyway, this is a 5/16, and so I'm going to connect one to the back here. This is the total pressure and then this is the static pressure here, so we have static pressure, total pressure.

So now I just take the total pressure this end here and I connect this to the positive side, which is this port right here. It's imprinted here on the top, it's just a little hard to see in the video, so this is positive and this is negative, so total pressure is going to positive, like that. It was tempted to say like so, but we're not doing that here. This isn't a cooking show and then the negative side here so now we've got both of them connected.

You can actually see here, they're, really pretty snug. I mean they're they're, just they're just pressed fit on, but they're really not going anywhere. I mean. If this, I could hang this by the hoses, and it would be ok not that I would do that, but it falls off the duct with the magnet it's ok if it hangs, and then it's connected here now, it's time to do our Traverse.

First, I'm going to set down the AC system and get it get it running up to this high of output volume, as I possibly can. One thing to note is that anytime you're doing a duct reverse we're really almost any measurement that the resolution of the gauge tends to increase as the volume increases. So when you're, taking a very, very fine reading with less volume, the resolution isn't going to tend to be as good in this particular case. Since we're reading in a small 8 inch duct I'm going to take the readings a couple times and just see what I get after after a couple tries alright.
So this is the duct that I'm going to be taking reading on and it's 8 inches. Generally speaking, you want to be as far away from a transition point as possible in this particular place. Where we're pushing it a little bit, so there will be a little turbulence in the duct play. I just chose the point equidistant between the transition and the outlet.

So I've already gone ahead and made my holes, which and a roundup is significantly easier than doing a a duct Traverse on a rectangular duct, because we only have to make two holes. You just make one on each axis, so I'm going to go through here and then through here average the tool and see what we get all right. So I'm going to go ahead and open the test, two smart probes, app and right now you can see that it's not on. So neither these are on, but I'm going to go ahead and turn it on and then it will.

It will search and it will find and connect. Ok, so you can see that we're at point: zero. 4 inches of water column right now, but in order to make it even better, I'm going to go ahead and I'm going to zero out the pressure sensor. All right so now we're completely zeroed out now before you do that.

Obviously you want to make sure that you're in handy I want to make sure now your hoses are kinked or anything, but I've already done that. So now we're at point: zero, zero inches of water column and now we're going to switch the mode away from basic view, which just shows the basic readings of the sensor to volume flow duct. And we need to go. And we need to check the diameter here.

So we can figure measurement go inside the diameter which I've already done. You can set rectangular or round. You can set multi-point single or time average and we're going to do time to average we're going to do the default density calculation. If I wanted to adjust in four for temperature for relative humidity or for very much pressure, I could go in and set in specific density by setting in temperature and ambient pressure, so we're at supply air 8 inch round time to average.

Okay, all right! So now I'm ready to go ahead and take my reading now when I start taking my reading, what I'm going to do is I'm going to hit this play button right here and that play button will start the time actually I'll. Do it right now. Just so you can see, it will start the time and the timer will run for as long as it takes me to do the Traverse and then, when I'm done with my first reading, I'll hit pause and then I'll go through and attempt to do it at The exact same pace sort of that way, let's say, took nine seconds for the first rivers. I want the second one to also take nine seconds and then, when I'm all done, then I hit the stop button.
I'm gon na hit stop here. I'm gon na go and do a new reading. If you continue the current from it will just be discarded. I wanted to because I didn't read anything there.

We go so now we're ready so we're reading at zero right now I take the pitot tube and remember. This is total pressure. This is static, so these are the static port. This is the static port, total pressure and the total pressure coming in the end.

So we're going to go ahead now and stick this up on top, and the main thing to remember is before you start measuring that the main thing, but one of the main things to remember before you start measuring you get up, send it all the way to The end then hit the play button and then slowly but steadily pull it out. That took me 13 seconds so that one's we're going to try to replicate the same and you'll notice again and that I'm really just focused on keeping this as level as I possibly can and going out as steadily as I possibly can. I'm also wanting to make sure this this hose likes to kink on me a little bit here, so I'm just liking to make sure that it stays open because it's important that it stays open. So there we go or nice, and even now I'm going to attempt to do this in 13 seconds Oz.

So I took me it took me a little more than that, so I have total of 30 seconds didn't quite nail that one, but now I'm going to hit the go ahead and hit the stop button. So let me give me my readout, so it's giving me 236 CFM at 678 feet per minute. So in how did I get dropped? Some older boys going to hit play slides? I can keep it the end pause times. 11 seconds says a little faster.

You can play cause 24 seconds, didn't quite nail at that time, but see what we get. If you look here reading zero now, because we're not in deduct 24 seconds now, I'm going to hit the stop button here and it calculated slightly lower. You can see that p.m. feet per minute, slightly less or do one more time see what we get, and this time we read 174 CFM, so we're all all generally within the same range.

So that's it! This is the test. Oh 510. I digital manometer with bluetooth, and this is a pitot tube and you can use it to calculate your airflow and then, once you calculate your CFM, if you did it say on the entire system, you could then calculate your enthalpy and come up with your total capacity. So, that's it! That's how you use the test of 510 eye to calculate velocity pressure and static pressure and CFM using a pitot tube again, I want to remind you that a pitot tube is not a static pressure.

Tube a pitot tube has an open end and it has the l-shape connection at the end. That's how you can tell it's a pitot tube, a static pressure tip does not have an open end and it only has the straight adapter. So don't confuse the two. Otherwise, it's not going to work at all the other thing to know about the 510.
I, like, I said, is you can use it for regular pressure, readings, regular pressure, readings and whatever pressure scale that you choose - and I didn't show you the setup of this. But it's fairly simple within the testo app you just go in and set up what pressure scale you'd like to read, but in general, as you know, we read water column and all you need to know is because it is a differential manometer. If you're reading positive and only positive, you don't want to read differential, then you just connect to the positive side if you're reading negative - and you only want to read negative like say, for example, if you want to read the static pressure on a return side, duct And see what just the return side is. If you want to find an airflow restriction across the return side, then you would just use the negative side, and the same is true: if you're reading static pressure on just the supply side, you would do just the positive side when you connect both that's when it Shows the differential between the two - hopefully, this was helpful.

As always, you can go to true tech tools comm to find this particular product, as well as the pitot tubes and many other things. It's also where you can find the link for the duct Traverse for rectangular ducts, because laying out the duct Traverse, while on roundup, is fairly easy on a rectangular duct. You have to make sure that you get the points in the right places, and so they have a great sheet there. That shows you how to do that and there's also some other videos that have been done, that do some specifics on how to do a rectangular.

Duct: reverse thanks for watching I'm Ben Brien war with HVAC our school comm and the HVAC school podcast doing this video in conjunction with true tech tools, comm use the offer code, get schooled a true tech tools, calm for a great deal on any of your tool; Purchases.

12 thoughts on “Reading duct velocity pressure, cfm and static with a testo 510i and a pitot tube”
  1. Avataaar/Circle Created with python_avatars Napo Guevara says:

    👍🙋‍♂️

  2. Avataaar/Circle Created with python_avatars David S says:

    Which app do you use that shows barometric pressure in PSI? The only ones I can find all show inHG and I can't find a conversion chart that converts inHG to PSI.

  3. Avataaar/Circle Created with python_avatars vconcerned says:

    236, 173, and 188 CFM are not in the "same" range", not even close. That's a variance exceeding 25%.

  4. Avataaar/Circle Created with python_avatars Quang Nguyen says:

    236 cfm – 173cfm thats a huge different? can u compare using vane anemometer Are you in Nepean ?

  5. Avataaar/Circle Created with python_avatars idris allen says:

    Can you re-do this with the testosterone hot wire probe?

  6. Avataaar/Circle Created with python_avatars maaz khan says:

    Can u please make a vedio about static pressure and it's importance in Hvac , like it's exact definition, how to maintain, how to measure ? Why it is needed ? Difference between static pressure and external static pressure??

  7. Avataaar/Circle Created with python_avatars Bob Lacy says:

    B(*

  8. Avataaar/Circle Created with python_avatars Howard Katzman says:

    Is this approach at all accurate at residential duct velocities?

  9. Avataaar/Circle Created with python_avatars wait just a minute says:

    That 8" sure looks like 10" to me

  10. Avataaar/Circle Created with python_avatars Cubby McElrath says:

    Great information Bryan
    Thank you guys for your time and effort to better the industry
    As a technician and electrician one of the hardest arguments that we get is “it’s working or it’s worked that way for years”
    You guys are giving us the knowledge and information to know and act otherwise
    Thanks so much

  11. Avataaar/Circle Created with python_avatars James Crawford says:

    Brian, this forms a great intro to the Testo 510i and pitot tube!  Can you tell us the minimum duct  diameter the app permits?

  12. Avataaar/Circle Created with python_avatars vegas hvacr guy says:

    great videos great explanation thank you for your time with these videos and the podcast , i live in Los Angeles i get stuck in traffic all the time so i always listen to your podcasts
    i have a question am going for the refrigeration side am just wondering do u have any podcast about how to adjust pressure switches on refrigeration units ?
    thank you Service area Ottawa??

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