HVAC Design Mythbusting #LIVE

HVAC School - For Techs, By Techs

Bryan Orr

Education, Business, Self-improvement, Careers

4.9 • 1K Ratings

🗓️ 17 February 2020

⏱️ 45 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

Alex Meaney from MiTek/Wrightsoft joins us at AHR 2020 to talk about some HVAC design myths and how to bust them in your mind. It was a really fun talk with a great guy.

One common HVAC design myth worth busting is that we can use a set friction rate with a Ductulator to make duct systems work. The friction rate only applies per 100 feet, and it has different degrees of impact based on duct sizing and fan speeds. We CANNOT guarantee that a system will work if we subtract losses to filters, coils, and grilles until we reach a set friction rate (usually 0.1 or 0.8). We experience most of our pressure losses at the fittings, which the friction rate doesn't account for.

To prevent some of these myths, we can move away from manual math and start using more software. However, we have to know what our numbers exactly are and what the performance conditions are. For example, filters can show a static pressure drop rating of 0.1, but that WILL change depending on the CFM.

Velocity is a confusing area for techs because we have face velocity and duct velocity. Face velocity refers to the speed of air at the register whereas duct velocity refers to the air speed within the duct. These can get a bit complicated when you throw dampers in, but duct velocity doesn't have that much of an impact on the face velocity; the register has a much greater effect on face velocity than a damper in the middle of a duct.

Alex and Bryan also discuss:

Starting off by learning the wrong thing
12,000 BTUs per ton
Radial duct systems
What really is "static pressure?"
Oversizing ductwork
Creating vs. relieving friction
Manual D
Ideal velocity
Variable-speed technology
Efficiency vs. moisture removal
Sensible heat ratio (SHR) and Manual S
Latent loads

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Transcript

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0:00.0	So this is one of many podcasts recorded live from AHR Expo 2020 here in Orlando.
0:09.9	My hometown, HR was nice enough to allow us to record and to set up some great equipment for us.
0:16.3	So big thanks to AHR for doing this.
0:18.4	It's been a great event.
0:20.1	Thank you to all of our sponsors, Field Piece, Carrier, Navac, Refrigeration Technologies,
0:25.9	and Speed Clean for making this podcast and all of our podcast possible.
0:30.4	But most of all, thank you to everybody who participated in these episodes and who came up and said so many nice things about what we're doing at HVAC school. Hope you enjoy. And now your host, the guy who starts all his limericks with, there once was a man from
0:49.0	Nantucket, and still doesn't cuss. Brian Orr.
0:53.3	Hey, this is Brian and this episode of the HVAC School podcast is definitely
0:58.6	there to help you remember some things you might have forgotten along the way as well as
1:01.2	help you remember some things you forgot to know in the first place because this is with Alex meany from right soft and Alex is one of the
1:07.0	Maybe the most interesting guys in hvacr. I'm not sure. I don't know how you measure that sort of thing, but I think he's great and he did a really great job of teaching on this exact topic at our symposium
1:17.3	So I asked him on to the live stage at a HR to talk a little bit more about it. This is more of a conversation than a training, but we do talk through some common
1:25.9	HVAC myths, design myths, ductwork, and system sides. So hope you enjoy the great the unparalleled Alex Meany
1:36.6	Alex Meany Alex Meany with my tech.
1:38.3	Yep my tech right soft my tech owners of right soft.
1:42.4	Yeah.
1:43.4	Thank you for joining me on the podcast again.
1:44.7	It is my pleasure.
1:45.8	One of the more requested guests on the podcast.
1:49.1	Flattering.
1:50.1	Yeah, it's kind of a big deal as I often say.
	...

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