Dose anyone have experience testing high velocity duct systems?

I've been asked to duct test a Zhender HRV with comfoducts (2" homerun ducts).

I designed & installed a hydronic high velocity system a few years ago. It had 25' of 12" return flex duct, and 15-20' of 6+8" sheet metal ducting, 2 + 2-1/2" branch ducting. I sealed everything with mastic.

I installed the duct tester at the return, and the duct pressure at the nearest supply to the air hander, as I would on a low velocity system. I measured a high duct leakage, I was disappointed. I'm wondering if I should have taken my duct pressure at the supply trunk (6-8") rather than the 2 - 2-1/2" ducts, due to pressure drop.

Any thoughts?

Thanks

 

Views: 395

Reply to This

Replies to This Discussion

This duct system should be tight enough that it should not matter where you test it from.  I recommend you test under negative pressure to ensure you get good seals at the registers.  How high was your reading and what flow range were you on?

When measuring super low flow, do a field check of your duct tester (thank you for not calling it a Blaster) by cutting a 1 inch x 3 inch hole in thick card board and tape it to the flange on your duct tester. This hole should come in at around 16 cfm at 25 Pa with the pressure measured across the cardboard.  If it measures more than that, your duct testing system could be leaking or out of whack some how. 

if the duct leakage is relatively low, 200 cfm or less, the pressure in the duct system will be quite uniform and either location will give consistent results.  If the duct leakage is high, over 500 cfm, we recommend that you do two tests.  One with the probe in the supply register closest to the Duct Blaster setup and one with it in the farthest supply register and average the readings.  

RSS

Forum Discussions

Tankless Water Heaters... has their time finally come?

Started by Bob Blanchette in General Forum. Last reply by Stanley Layman 1 hour ago. 33 Replies

How would you insulate this roof?

Started by David Butler in General Forum. Last reply by John Hatfield 16 hours ago. 9 Replies

Psychrometric Chart Training

Started by John Krochmalny in Training yesterday. 0 Replies

Dirty solar panels

Started by Evan Mills in General Forum. Last reply by Stacie Bagnasco on Monday. 1 Reply

Latest Activity

Marc Tannenbaum's blog post was featured

3 Issues HVAC contractors Should Know About Impacting Customer Comfort and Health

There is an epidemic of people suffering in many of the 100 million homes across the U.S.  Many of…See More
37 minutes ago
Profile IconPaigh Bumgarner, Blake Reid, James Barras and 3 more joined Home Energy Pros Forum
44 minutes ago
Stanley Layman replied to Bob Blanchette's discussion Tankless Water Heaters... has their time finally come?
"A tankless water heater can be a bit pricey. Tankless water heaters can range from $300 to $1100 or…"
1 hour ago
John Hatfield replied to David Butler's discussion How would you insulate this roof?
"David I think the finish edge application is critical but several un-knows exist. Such as how far…"
16 hours ago
David Butler replied to David Butler's discussion How would you insulate this roof?
"@Kevin, that article is behind a pay wall. Here's the original posted on Allison's…"
17 hours ago
Kevin Miller replied to David Butler's discussion How would you insulate this roof?
"Good question.  I don't know the answer.   I'd love to know whether there…"
17 hours ago
David Butler replied to David Butler's discussion How would you insulate this roof?
"Hi John, thanks for pointing out my faux pas: I made clear in my original post that rainwater…"
17 hours ago
John Hatfield replied to David Butler's discussion How would you insulate this roof?
"Kevin, Is the "Kool Seal" product certified for potable water collection?"
17 hours ago

Photos

  • Add Photos
  • View All

© 2017   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service