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Community and Q&A

Duct blasting a ducted indoor unit of a minisplit system

pioneerbuilders | Posted in Mechanicals on
Our company exclusively installs Daikin units in our new construction homes. There is generally one or two indoor units and a ducted unit in the attic.
I’m not sure, but I think the ducted portion of the system is low static pressure. 
No jurisdiction has had us test these systems. However, I already own a Minneapolis blower door, so I got a duct blaster. 

We’re in Washington state under the Washington State Energy Code. 

What I’m experiencing is the pressure flowing into the ducts from the duct blaster is so high that the temporary sealing of the supply and return ducts doesn’t stay adhered.
What I’m hoping is that these types of systems aren’t required to be tested by code but that I can do it for my own purposes. 
Maybe I’m missing something too, it could definitely be user error.

I used some UL rated tape at the air handler and discovered one duct that needed some foaming in the attic. Otherwise, there didn’t seem to be anything egregious. 

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  1. GBA Editor
    Martin Holladay | | #1

    I imagine that a GBA reader will soon post some advice for you on this topic. In the meantime, you should contact a technical representative at the manufacturer of the Duct Blaster:

    The Energy Conservatory
    2801 21st Avenue South, Suite 160
    Minneapolis, MN 55417

    The employees of The Energy Conservatory are well-informed and helpful.

  2. user-626934 | | #2

    Rotate the fan and depressurizate the duct system. Leakage rates differences between pressurization and depressurization are typically within a few % of one another in duct systems I’ve tested. I’m pretty sure most (all?) energy codes in the U.S. do NOT stipulate positive or negative pressure.

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