HVAC Tech School: How to Read AirFlow Differential Pressure?

In this HVAC tech video, we show you a couple of different tools you can use to check airflow differential pressure. Knowing what the pressure difference between your supply and return can give you the information needed to troubleshoot HVAC systems.
I will show you the tried and true Dwyer Magnehelic and show you how the internals work. I also give you some recommendations on handheld blue tooth devices. So check it out, give us a like, and subscribe to our channel.
Stromquist & Company: www.stromquist.com
Click here and read a detailed blog post on how to use Magnehelic gauges to troubleshoot HVAC systems. controltrends.org/hvac-smart-...
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Video Transcript: Hi Control Trends Community. This is Eric Stromquist with controltrends.com, your source for smart building in HVAC control news you can use. We get a lot of questions on the website about Magnehelic gauges and how they work. I think about it this way. The doctor checks your blood pressure for a reason because basically that pressure allows the blood to flow from your heart through your body. If you get a card, you got a problem - same thing with your buildings and same thing with your homes. If restrictions, like dirty air filters or other restrictions, keep the air from flowing, then you have to troubleshoot it because the tenants are not going to be happy. So how do you do this? Well, in this video I'm going to talk about the tried and true the Dwyer Magnehelic gauge. So check it out. So short video, watch it till the end.
If you like it, please subscribe to the KZbin Channel and give us a lot. Okay, so let's look at the basic Magnehelic gauge and as you can see it's a couple of things, just a set of magnets. It is a center that's senses the differential pressure, the static pressure, and then it's a helix that wind and unwind as the magnet is pulled from side to side. You can see how this works in this particular little video clip here. Okay? You can use these gauges and a lot of different ways. Typically what you're going to use it for is to diagnose airflow problems, uh, in a unit. So to do that, you'd be putting a pitot tube or some soother type of airflow sensor in the supply return air streams. And the most important thing to remember is the pitot tube that must be inserted at 90 degrees and points into your air flow, if you get it backward, that'll measure readings up.
Okay? So once you get the supply and the return hooked up, you are ready to go? You can either read it directly off of the specs of your equipment to get the differential pressure rating that the equipment will operate at optimally. If it's not in that range, then you know you've got a problem. It could be dirty air flow filter, or something could be clogging up your duct work. Okay. Many, many uses of this. You can use it on your uh, AC units, your furnaces, you can use in commercial applications too, but it's all based around the airflow pressure. You got to get the airflow through the system. Now Stromquist Company, styromquist.coim, we still stock Magnehelic gauges and even sell lots of the Dwyer Magnehelic gauges, because it is one of the all-time great differential pressure gauges and it still works well.
A lot of people have a popped over to the electronic ones, that we stock as well, and there are a couple of other great brands. The same principles apply, but now you get an electronic reading and can even use Bluetooth, and you can use your phone to do your diagnostics. Okay. So I will put some links, with some Magnehelic and electric meters in the notes below. So if you're looking for a Magnehelic pressure gauge, click the links, take you right to stromquist.com website. All right, if you liked this video, please subscribe to our KZbin channel and give us a thumbs up. If you have any questions, reach out in comments.

[@ryankilgore6407]

Good video, thank you for posting. One minor technical detail, the angled probe shown in the video (closed tip that is pointed into the airstream) and commonly use for static pressure pressure testing is not a pitot tube, it is a static pressure probe. A pitot tube is used for measuring airflow. It has a hole in the tip (pointed into the airfstream) to measure total pressure and another set of holes to measure static pressure. The static pressure is subtracted from the total pressure to calculate velocity pressure, which is used to calculate airflow.

[@coldfinger459sub0]

It’s about time would like to see you do more hands-on videos of practical usage of equipment correlating with the efficiency of the building and automation systems put into use. Testing and measurements

[@EricStromquist]

Thanks so much for your comment! Are there any training videos you would like us to make?

[@JustinCrediblename]

is there a reason not to permanently install one of these near the air intake and just leave it there?

[@nicklaham4515]

Does it matter which way the 90 degree angle pressure tube is facing inside the duct? Do I face the tip at the direction of air flow?

[@1Akanan1]

If using a digital manometer, what unit to use to find the DIFF (DeltaP) on a HRV? Thank you

[@mikaelmullarkey3931]

I have the gauge can some one please help and send a link for good probes?

[@nickledimez4012]

What about the increments on the gauge mean.

[@user-tt5pz4wn1x]

So pretty much tells you if your filter is clogged or based on the flow of air

[@mohamedallam958]

if magnehelic gauge measure the differential pressure for water also??? because i have pipe filled with water and i want to measure the differential pressure between inlet and outlet for water ???