Short #64 - Diagnostic Duct Design
HVAC School - For Techs, By Techs
Bryan Orr
4.9 • 1K Ratings
🗓️ 23 July 2019
⏱️ 19 minutes
🧾️ Download transcript
Summary
Balancing complaints are common in the HVAC industry. In this short podcast, Bryan explains how diagnostic duct design solves those issues.
"Diagnostic duct design" refers to using the duct system to locate and solve a customer's comfort problems. If a couple of rooms have problems with humidity control, then the duct system could be a culprit. However, before we even touch the ducts, we should look at the space to determine if we have issues. For example, radiant gains from a window could be contributing to comfort problems, not the duct system. Airflow may also not be an issue if comfort at night is an issue. That's a matter of the equipment cycling less often at night, and we can solve that by reducing the setpoint at night.
When we look for duct issues, we want to assess the pressure. You can do very simple tests with a manometer (or a qualitative test with tissue paper under a door crack) to look for pressure imbalances, which can cause discomfort in rooms where the door is closed very often. Flow hoods are good for assessing airflow, but you can also get an airflow approximation by measuring air velocity. Make sure you're hitting your targets; then, you can check your static pressure.
Since distributed airflow is a major comfort factor, you can take the total CFM and divide it by the square footage (factoring in each room's square footage) to determine the airflow distribution. Remember: Perimeters require more airflow than the centers of rooms, and rooms with more windows will have greater radiant gains to account for.
When you can't redesign the entire duct system, use balancing dampers in oversized ducts to help balance the airflow. (Make sure the register isn't oversized, though! Try to keep the static pressure down, too.)
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Transcript
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| 0:14.0 | Hey, this is the HVAC School Podcast. This is a short episode. And in this short episode I'm going to talk about diagnostic duck design, which isn't a real thing because it's not really design it's more so just being able to diagnose a problem and then fix it for a |
| 0:18.0 | technician to the field but just for the sake of a title we're going to call |
| 0:21.4 | diagnostic duck design but before we get into it I want to |
| 0:23.4 | thank our sponsors and our sponsors are fieldpiece and fieldpiece.com if you haven't |
| 0:27.1 | taken a look at the SM 380V that is a standard manifold it's not a fourport, but it has all kinds of features that you're |
| 0:34.2 | going to like. It has a great hook. It has the ability to do superheat subcool, all kinds of stuff, |
| 0:40.5 | like any digital manifold you would expect, but it doesn't in a really nice form factor, |
| 0:45.3 | very water resistant, the probes attach into the back. It's just a great design. From an industrial design |
| 0:51.1 | standpoint, you're going to really like the SM 380 v by field piece. |
| 0:55.0 | I also want to thank navac and navac global.com if you haven't seen the NRDD recovery machine |
| 0:59.7 | you're going to want to take a look at that kind of a a leading product in the industry. It just does everything well. |
| 1:05.0 | So that's the NRDD speed clean. Speed clean. |
| 1:07.8 | speed clean.com makes a lot of different stuff but one product that I really like is the |
| 1:11.6 | coil bib kit if you're cleaning |
| 1:13.0 | duckless systems look at the coil bib kit from Speed Clean there are other |
| 1:17.1 | knock-off products in the market that aren't nearly as heavy duty not nearly as |
| 1:20.5 | thick I've seen them side by side. Speed Clean is the way to go and their |
| 1:24.7 | bib kit for cleaning, duckless air handlers. Refrigeration technologies, RefrigerateTech.com, they make all kinds of great |
| 1:31.0 | stuff. Use Viper Cleaners for Pete's sake. If you haven't at least tried them, then try them. |
| 1:35.6 | If you try them and then you don't want to use them, then that's fine, but give them a shot. |
| 1:39.1 | They are a great company and they support the industry. |
| 1:41.8 | And then finally, carrier and carrier. And then finally carrier and carrier. |
... |
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