Last week I was doing a rough-in w/air handler installed duct test.  I taped all the supply boots and installed the fan to the return grill just as always. When I set up the manometer, I noticed a pressure reading of 135Pa, this without the fan being turned on.  If I disconnected the hose from the manometer, pressure fell to zero.  Assuming I had done something to cause this I checked and rechecked everything, even installed fresh batteries.  Finally, I moved the hose to another supply boot, this resulted in a proper reading so I went ahead with the test.

Does anyone have any idea what was going on to give such a reading?  Let me know if you need more information.  Thanks for help solving this perplexing question.

Views: 362

Reply to This

Replies to This Discussion

Hard to see how there could be +135 in one supply duct without at least some positive reading everywhere else. Maybe someone accidentally (?) tied a bath fan into that duct.......

No power to the house at time of testing.

someone stepping on the hose?

No.

I would tend to agree with Glen, as a blocked tube will clock up rather fast.  If there is still a pin hole I suspect the pressure would stabilize at some point, although I'm not going to test it.  It could have been a kink somewhere that unfolded when you moved the hoses.  If it was a positive pressure the block was on the input.  If negative it would have been on the reference, DG700 at least.

Bud

I just submitted this to the Energy Conservatory.  If I get something useful back from them, I'll post it here.

As promised, I asked the folks at The Energy Conservatory about my funky duct test results.  Paul Morin, a Technical Sales Specialist suggested that such a situation could occur if the hose is stopped up or perhaps was up against insulation in the supply boot.  He went on to say; "You can simulate a pressure this high by putting your finger over an open tap on the DG-700 gauge.  It is harder to reproduce a pressure that high with a long length of hose attached, but you would see pressures that high if some debris is plugging the hose.  You also will see pressures that high if the hose is pinched, stepped on or if there is water in the hose."  

I believe that the end of the metal probe must have been up against the boot insulation, probably when I taped the hose  to secure it. The resulting restriction of air caused the errant reading.

Thanks to everyone who offered a suggestion.  

Something else to look out for.  If you use the metal probe to punch through the plastic tape you can actually punch a hole in the plastic tape which will cover the end of the probe.  I've had this happen to me and it caused some temporary confusion.

RSS

Featured Forum Discussions

Too many BTU's. Too much horsepower?

Started by Steve in General Forum. Last reply by Eric Kjelshus on Saturday. 4 Replies

Stack/wind pressure and flow networks.

Started by Daniel James Grundy in Training. Last reply by Daniel James Grundy on Thursday. 5 Replies

BDT with vermiculite in hollow CMU walls?

Started by Brad Cook in General Forum. Last reply by John Nicholas on Thursday. 2 Replies

Strange IR Image

Started by Larry Nissman in General Forum. Last reply by Brad Cook Mar 9. 7 Replies

Videos

  • Add Videos
  • View All

Latest Activity

Mike Rogers replied to Quinn Korzeniecki's discussion Don MacOdrum Receives BPI's 2017 Tony Woods Award and Four Others Inducted in to Hall of Fame in the group Building Performance Institute (BPI)
"Congratulations to Don! A deep thanks for the honor--and even more thanks to the many who've…"
4 hours ago
Mike Rogers joined Building Performance Institute's group
Thumbnail

Building Performance Institute (BPI)

BPI is the nation's premier standards development, quality assurance and credentialing organization…See More
4 hours ago
Horace Douglas Hunt, Jr. replied to eric anderson's discussion Energy auditing equipment for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Have you sold this or still interested in sales of this equipment?"
7 hours ago
Charles Maier is now a member of Home Energy Pros
16 hours ago
Derrick Brodanex joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
yesterday
Eric Kjelshus replied to Steve's discussion Too many BTU's. Too much horsepower?
"Its more about run time with high RH removing, than to large over sized AC unit, in houses.  …"
Saturday
Sarah OConnell posted a blog post

Crowdsourcing for Innovation

Share Your Ideas!Novel Building Envelope Design for Increased Thermal PerformanceIn 2014, more than…See More
Friday
Colin de Paor is now a member of Home Energy Pros
Friday

Home Energy Pros

Welcome to Home Energy Pros – the unique digital community by and for those who work in the home energy performance arena.

Home Energy Pros was founded by the developers of Home Energy Saver Pro (supported by the U.S. Department of Energy) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network. Please honor our Guidelines

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service