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Ultimate Air 200DX very noisy

airfix | Posted in General Questions on

Nearing the end of my build and finally fired up the Ultimate Air 200DX and boy is it loud.  It sounds like a jet engine going off in my house.

Here is a link to a video of it in my living room vent:

The installer has not yet balanced the unit and set the adjustable apertures yet.  The dial is set a little below half way (I assume a little less then 100cfm) in that video.  When it is on boost mode it is easily twice as loud as this.

We have flex ducts directly out of the unit to the first 4″ diameter sheet metal duct.  All ducts in the walls are 4″. 

Any tips on what might be causing this?  Maybe dirty filters?

Edited for typo

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  1. DevinCarlson | | #1

    Is the trunk duct metal and what size is it? How long is the flex duct from the unit to the trunk and is it the same size? How many supply and return ducts do you have? Properly ducted, you shouldn't be able to hear much at the grilles, even on boost mode.

    The trunk should be at least an 8" round metal duct with five or more 4" metal supply ducts and an equivalent amount of return.

    Checking to make sure that the filter isn't plugged is always a good idea!

  2. airfix | | #2

    I think the trunk duct is metal. I'm pretty sure it is 6" because I think that is what the ERV connection is. The flex duct is about 3 to 4 feet to the trunk however it is in a tight space and is quite convoluted.

    We have 4 supplies and 5 exhausts. The supply and exhaust flow rate is balanced at 115 cfm supply and 115 cfm exhaust.

    One thing I noticed is they did not suspend the unit from rubber bungees as shown in the installation manual. They used steel U channel and mounted it right to the ceiling joists.

    We are fully sheet rocked and painted so I'm worried I won't be able to fix whatever is causing the problem.


    1. DevinCarlson | | #3

      Definitely verify the diameter of the trunk duct. A single 6" round is way too small to quietly handle the 200 CFM the unit is trying to deliver on boost mode. Four 4" supplies is also short.

      "UltimateAir recommends a minimum of a 7” to 6” taper reducer at all four collars. Some installations will require 8” to 6” tapered reducer for running 8” trunk ducts."

      Installation manual:

      Ducting guide:

  3. airfix | | #4

    It turns out my builder confirmed there are 8" flex ducts going to an 8" trunk line.

    I couldn't find your quoted text in either of the manuals.

    I'm not sure what you mean by four 4" supplies is too short. You mean we should have more than 4 supplies? It's my understanding that I would put supplies to my bedrooms, dining room and living room. Where else should I put a supply? Hallways?

    How will adding more than 4 supplies help with the noise? I assume you are thinking that I'd up the whole house balance from 115 CFM to something more by adding another supply?


  4. Expert Member
    Akos | | #5

    It sounds to me like fan noise, which is surprising if it is far from the unit especially with a bit of flex duct in between.

    You can narrow down where the noise is coming from by disconnecting one of the feeds to the bedroom near the main trunk. If it is noisy there, it is coming from the ERV unit. If it is quiet, than it could be some ugly ducting near the diffuser.

    If it is the ERV unit, you can try installing a duct silencer near it or, if you have the space, a smaller one for each bedroom.

    50CFM is a bit on the high side for a 4" supply but it should not be that loud. If the ducting just before the diffuser is ugly, the ~600FPM while running on boots could create some noise. If you can get it down to under 400FPM on boost (adding 2 more supplies elsewhere in the house) should be significantly quieter.

  5. airfix | | #6

    The duct where the video is taken is probably about 25 feet straight line distance from the unit. It sounds to me like it is the unit making the noise too. My mechanical room is super tight and I don't think I have room for silencers. They are 20+ inches long.

    If I have 8" pipe delivering 115 cfm then that's 329 fpm,
    When that splits to the 4" pipes then at 28.75 cfm that's the same 329 fpm doh! Pi D^2/4

    I did notice that there was some screws penetrating into the duct work, I'm sure that doesn't help.

    It will be hard to add 2 more supplies as we are fully sheetrock and painted and supposed to be moving in on Friday :(

    Can you set the boost so it doesn't run at 100%, maybe just 75% flow rate?


    1. Expert Member
      Akos | | #7

      You'll have to check with the manufacturer. The ones I've used had an option for setting boost flow rate.

      If you are tight on space one option is to do an S bend on the flex right out of the unit. This is fairly restrictive but with 8" trunk, it shouldn't add too much restriction at nominal flow rate.

      You can also get one of these transfer ducts and cut the insert core to fit into your existing trunk or bedroom diffuser. The honeycomb structure works quite well for stopping high frequency noise from the blower.

  6. MattJF | | #8

    I would start investigating right at the unit. This sounds different than most duct noise, but is hard to tell over video. Have the installer check the static pressures on each of 4 ducts. Fans can be noisy if they are flow restricted. You can also disconnect the ducts and see if the unit is noisy with no restrictions. You can also usually unplug each fan internally to run them independently to isolate noise issues.

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