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Community and Q&A

Question about the Panasonic spot ERV

Jamar Lambert | Posted in Energy Efficiency and Durability on

I work for a non-profit organization weatherizing homes. I live in the deep South, so ERVs provide good potential benefits in this region.

We’ve recently installed two of these units but were disappointed in the cfm reading we got. the unit is advertised at 40 cfm, however using the flow pan and manometer the highest reading I could get on this unit was around 11 CFM.

I was hoping to get some insight on this unit concerning this issue. I could be testing wrong (i test at the site of the unit, but some contractors say I should test this unit at the outside exhaust), maybe we’re installing them improperly, or maybe the low reading is what we should expect.

I’d be very thankful for any information on this unit especially someone who is used to dealing with them.

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    The most common cause of disappointing airflow with any ventilation equipment is restrictive ductwork -- that is, undersized ducts, ducts that are too long, or ducts with two many elbows.

    Check the installation instructions provided by Panasonic to be sure that the ductwork meets the manufacturer's recomendations.

    If the ductwork checks out, you should call the technical help hotline at Panasonic to get advice from the manufacturer.

  2. Jamar Lambert | | #2

    thank you Mr. Holladay for your insight

  3. David Meiland | | #3

    I'm curious how you would test this unit at the ceiling grille. Isn't air flowing out of and into the unit at the same time? If you place an exhaust fan flow meter over the grille, you are going to be getting a reading that combines the pressures created by both flows.

    Were you able to somehow isolate the exhaust (outgoing) air flow and measure that, without affecting the incoming air flow?

  4. Jamar Lambert | | #4

    Mr. David Meiland what you're suggesting makes sense. I've tested many exhaust fans in the past but this is our first experience with the spot ERV by panasonic. Its becoming clear that I'll have to be flexible in my methods regarding this device.I wonder if you (or anyone else) has experience testing these devices. If you don't mind sir please email me on this subject or I could email you and maybe we could speak about this further. At my organization we try to provide the best possible results to our customers. We receive funds from DOE so we have to insure we are making homes energy efficient and complying with the latest Health and Safety regulation (i.e. ASHRAE 62.2) Thank you for you response to this question.

  5. David Meiland | | #5

    I don't have experience testing those devices. I took a look at this manual

    and it isn't totally clear to me exactly where you would measure exhaust airflow, but it does seem clear that supply air is coming into the room from one area of the grille (see the attached diagram).

    So, if you cover the entire grille with a flow box you are not getting the reading you need. You might be able to remove the grille and place the flow box over a portion of the mechanism to get a reading. You might have to use masking tape or something else to correctly isolate the exhaust area without interfering with the supply area.

    If the units you are testing have two separate exterior wall caps, then I would put your flow box on the intake cap. This can be tricky depending on height above ground, siding type, etc.

    If the ducts are in the attic, then you can try to get a reading by inserting a manometer probe or an anemometer into a hole in the duct (which you have to drill and then seal).

    I would certainly call Panasonic and ask them how they would do it.

  6. Jamar Lambert | | #6

    great points, thanks again Mr. Meiland

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