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Balancing an HRV

Erik Olofsson | Posted in General Questions on

Our HRV is installed, the ducting sealed, and the wall/ceiling diffusers are in place. I still need to balance the system so i armed myself with a couple of flow grids and a magnehelic gauge.

The balancing equipment seems somewhat straightforward (i hope) but my question is about the diffusers: where do i begin the balancing procedure? with the diffusers off? on but fully open? on but half open?

here are 6 diffusers: 2 in the crawlspace, exhausts in the kitchen and bathroom, and supplies in the bedroom and living room…thanks again

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Replies

  1. David Meiland | | #1

    To ask the obvious, what brand/model is it, and did you check the manufacturer for balancing instructions?

  2. Erik Olofsson | | #2

    it is a lifebreath 155ecm. i also wonder if i'm supposed to balance the 'cold' side of the system..?

  3. Erik Olofsson | | #4

    thanks david. however, even that manual doesn't mention if you are meant to restrict the airflow with the diffusers before balancing the system..

  4. David Meiland | | #5

    It certainly seems like you would. Maybe call them on the phone and ask?

  5. Hobbit _ | | #6

    I worried about this until I got my Fantech installed and running
    for a while. I've learned that there doesn't really seem to be
    any need for balancing, especially at the fairly low ventilation
    rates I need to run. If the ducting in either direction isn't
    restricted or undersized, the HRV isn't likely to place enough
    imbalance on the house to worry about. If something *else*
    is causing a notable pressure differential in the envelope then
    the HRV is the wrong place to try and compensate for it; the
    cause should be directly tackled.

    _H*

  6. Gio Robson | | #7

    Erik:

    I could walk you through the basic process on the phone, but I can't find a way to private message you.

    Heads up - ventilation commissioning is part of the R2000 certification process and your R2000 inspector would normally do this for you. Did they not discuss this with you during their testing and inspection visits?

    Remember that to meet the R-2000 standard your ventilation system needs to be designed, installed, and commissioned to meet CSA F-326.

    Also, if your HRV was installed by a professional they should have already set and balanced it as part of the installation process.

    I hate using the term "balancing" - I think the correct term should be "setting and balancing" as you want the supply and exhaust flows to be balanced AND you don't want to over-ventilate or under-ventilate the house. Balanced flows are important not just to protect the envelope, maximizing comfort and efficiency, but also to avoid your HRV core icing up in cold temperatures.

    Do not ignore this absolutely crucial step. ALL HRVs need to be set and balanced.

    Does your HRV model not have door ports? You may not need the flow grids. Your manual explains procedures to balance using flow grids, pitot tube, or door ports.

    I guess you are not using a furnace fan or air handler to distribute your ventilation air but have dedicated ventilation supply ductwork?

    Gio
    prairieHOUSE Performance

  7. Jane Smith | | #8

    I realize this is an old thread but I have similar questions to the original poster. My HRV is a Vanee 3000HE. As with this post, I also have adjustable diffusers. The manual does not make any mention of whether these should be off completely, partially open or closed. I have 22 of the suckers so they would have a large impact!

    Additionally, the installation manual indicates the flow dampers should be installed 'warm side', although many other HRVs seem to suggest installing dampers between the unit and the external wall. Does anyone know which is the best place? (I ask because installing warm side is space restricted due to distance between the unit and where the supply line splits to serve two different sides of the home).

  8. GBA Editor
    Martin Holladay | | #9

    Jane,
    Here is a link to the relevant installation manual: Installation manual for vanEE 3000 HE. The balancing instructions begin on page 17.

    All balancing adjustments are made at the two balancing dampers. To me, that means that your diffusers should be open during the balancing. Minor adjustments of the diffusers after the balancing shouldn't be much of a problem -- the air flow through each diffuser is small, and the unit will remain close to balanced.

    .

  9. Jane Smith | | #10

    Perfect. Thanks for that.

  10. Charlie Sullivan | | #11

    Two comments. First, starting with all the dampers wide open and only closing them a little if needed is a better strategy than starting with them half open and adjusting them in both directions, because it is best to have the overall flow impeded as little as possible. If the overall flow is higher than you want, selecting a lower fan speed is better than choking off the flow, so you want to use the dampers only as much as needed to achieve balance.

    My second comment is that one can evaluate balance through flow measurements at each vent, or though measuring the effect on the inside-to-outside pressure difference. I like the idea of measuring the inside-to-outside pressure difference and adjusting so that the system has no effect on it, because that directly confirms you aren't creating a problem, and because vent flow measurements are hard to make accurately, and some measurement methods can change the flow.

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