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Sourcing high performance registers

rajibroy | Posted in Mechanicals on

For a Vermont home (zone 6A), I using Fujitsu slim-duct systems to distribute air to multiple rooms. To balance the distribution system, instead of using dampers on branches, I am planning to use registers with flow modulation (such as opposed blade dampers).

My local supply-houses do not have opposed blade damper registers in stock (such as Truaire 210VO series, or Truaire 300 series). 

Can any GBA readers suggest of if
1. the “damper at the register” strategy works?
2. Is there any supply-house that can ship these?
3. How much penalty in pressure drop and flow modulation I will pay for using multi-shutter damper registers?

Thanks in advance!


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  1. walta100 | | #1

    Seems to me if you put the restriction at the register you will speed up the air flow at that point creating high speed air movement that reduce the human comfort level while generating noise in the room. With the damper the air slows quickly after the damper and a bend or two in the duct reduce the noise.

    Why do you want to avoid them seems like a low-cost line item on the bill of materials.

    Good register may well be a good investment but I don’t see them as a substitute for a damper.

    Consider upsizing the register for improved comfort.


  2. AndyKosick | | #2

    That's funny, those 210VOs are the exact register I was hoping to get for a project that I'm starting to test and commission right now. The HVAC contractor couldn't find them at any local supply house with the opposing blade damper, so I gave in and settled for the multi-shutter. Regretting that now.

    For context, this is a ducted mini with the duct system buried in a soffit (all in conditioned space and the ducts were pre-tested for leakage). Despite a manual D design reality is you're always going to need to make some adjustments at final and the opposing blade dampers seemed like the ticket, because there's no way to get at it except the register. If you'll be able get at the ducts an available inline damper can work fine.

    Now I'm having to pull some registers and add a piece a metal to restrict flow on a couple or else the vanes would be pointing air at the ceiling (or floor) and you can't get any throw. It's a pain. I would really try to get the 210VOs and let me know where you find them.

    ...and to address Walta's concerns, as long as you've got static and velocity down low like those slim ducted models want anyway, trimming the flow with a damper a bit isn't going to get too noisy.

    1. Chris_in_NC | | #4

      I haven't used that specific Dayus product, but I've got Dayus bar linear grilles in our house and can definitely recommend them as a quality product. Not perfect, but not a high-end price either, so (I think) a good blend of price and quality. Couple of weeks manufacturing/shipping lead time, but don't know if that's changed in the pandemic landscape.

      I will be buying more from them in the near future, as we start on a whole-house HVAC replacement this fall. They make a nice return air filter grill that holds a 4 inch deep filter, which is on the purchase list.

  3. Expert Member
    Akos | | #5

    I've use those Dayus ones and they work great. These are stock item at a number of local HVAC supply houses, very common for commercial systems so you should be able to find them locally.

    The one thing to watch for is they are quite deep. It won't fit into a standard end or angled boot unless you extend them a bit and set them back.

    Adjustment is with a screwdriver which is no problem for initial install but might be a pain if you are hoping to adjust it often.

    When closed, or near closed, they are much quieter than the standard stuff from the box store.

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