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  1. #1
    Join Date
    Mar 2006
    Posts
    254

    Quieting HVAC in small condo not easy

    Most know mine and others setup by now. Small 887 ft condo, new ac/furnace.
    The hallway closet right off the living room has a large return cavity below it.

    It was making a helluva noise. I tried lining it with 2" 80% cotton roll from a soundproofing net site. It did wonders for the sound...only...it sucked up
    the smell from that stuff.

    I know DASH has reply posted about vanes and right turns...but that just doesn't work when the HVAC closet is practically in your lap.

    I ran the AC and was gone for 4 hours...when I got back, I could "smell"
    that "quieting" material I bought off the net. Natch. Whatever I line my
    return cavity directly below my HVAC closet is going to transmit the smell of same
    thruout my condo. Lesson learned (imagine what the smell will be like when I run my furnace). I will now do as many suggested here
    and settle for lining that return cavity with nuetral smell plenum board/duct board.

    Question: Duct plenum/duct board has silver paper on one side...fiberglass
    in the middle..and a thin neutral smelling sound absorbing material on the
    the backside. Instead of having the silver side out, should I reverse it and
    have the sound absorbing part facing outward?

    Also, In my zeal to quiet my hallway closet HVAC, I lined it (after they lined the closet with ductboard) with a closed cell foam blocking/absorbing material. Again..off one of those "sound absorbing"
    net sites. Well...that stuff kinda stinks of "technology" as well. I may rip that out.

    Most here deal with big homes and well established systems and ductwork.
    Have pity on the small condo owner. Don't tell me that my AC company should deal with
    noise..cause they just don't want to deal with it. I do.

    Replies? Keep in mind my HVAC is in my lap...not down in a basement.

  2. #2
    Join Date
    Mar 2008
    Location
    Central Maryland
    Posts
    246
    Quote Originally Posted by caslon View Post
    Replies? Keep in mind my HVAC is in my lap...not down in a basement.
    Most foam materials off-gas for a while and then settle down, unless heated or exposed to solvents.

    Most cotton materials are treated with Lanolin at some point in their processing.

    You might try washing the sound absorbing material and letting it sit out for a few months.

    Curiously, it doesn't matter much which way a soft-sided panel is laid. When hit by sound from either side, the hard side will reflect much sound, and transmit the rest, and the soft side will reflect almost none and absorb only a little. The cumulative affect is about the same amount transmitted through from either side. The only difference is which side you get more echo on, well, that and aesthetics.

    -HF

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,755
    Its the roughness of the fiberglass that absorbs the sound.
    The fiberglass should face teh noise.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    May 2002
    Location
    Houston Texas
    Posts
    6,308
    BT why do you always spell the teh?

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    From your pictures,vanes and/or ductboard baffles could help.However you need a Pro to test the static,if you use baffles,due to the restriction the create.Ductboard for baffles.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,755
    Because my fingers seem to like spelling "the" teh.

    For what ever reason, I hit the E first before the H 60% of the time.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Feb 2003
    Posts
    1,996

    Is the furnace DV?

    Pulling combustion air from the space must allow the burner noise to filter in.
    A sealed combustion/DV system would have helped. Having the return directly
    next to the unit doesn't help. I suppose getting some return ductwork up into the ceiling
    is out of the question.

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Quote Originally Posted by beenthere View Post
    Because my fingers seem to like spelling "the" teh.

    For what ever reason, I hit the E first before the H 60% of the time.
    It's a common type-o. I find myself doing it, but I tend to edit as I go, backspacing and correcting "teh" to "the". Gets old after a few times. Microsoft Word does it for me when I use that program.

    For our condo dwelling friend, a consideration. If the condo has several bedrooms, and one of them is distant from the air handler, and the supply air noise within that room is acceptable, might that room serve your home theater needs? I've seen several dwellings where the home theater/media center was not located in the traditional living room spot, but elsewhere, which then made the living area more of a reading/relaxing/entertaining-conversational area.

  9. #9
    Join Date
    Mar 2006
    Posts
    254
    I guess I'll have the silver side of the plenum board facing out towards the sound, thanks for that advice.

    I still have that black closed cell foam lining the closet area.
    If I continue to detect any technology smell from that net bought black closed cell foam (no formadahyde used), I'll take that out and put in some more plenum board. I need to run the furnace to check for the smell. I ran the furnace for
    an hour and the warmest that fire retardant foam got was about like a heating blanket on full. The closet itself is pretty well sealed off from the return cavity, so I'm hoping no residual smell from foam will make into the system. If so...it gets yanked out. First things first tho...redo the return intake as that is where
    some of the smell is bound to be coming from. Not terrible, but noticable.

    I bet if I hung that 2" 80% cotton material on a clothes line for 6 months it would probably neutral out, but I don't have the place nor the patience.

  10. #10
    Join Date
    Apr 2005
    Location
    Tampa, Florida
    Posts
    1,634
    Okay, I'll bite. I'm just tuning into caslon's posts now....and am wondering... why is there a 2 ton system installed in 900 sq ft? Why are the vents so few & so small? Your system might be oversized (might be spot-on, depends on the heat load calc... tough call without seeing the place). At the very least, your ductwork and supply vents are far too small. Until you correct this, any other attempts to quiet this system will be useless.

    For comparison, here's an except from the engineering calcs on my system. I should note that everything was sized to handle 800 CFMs when doing noise calculations. The maximum air movement the system will produce is 770 CFM and will only happen at conditions not normally found in Florida. Normally the high stage runs 651-700 CFM, low stage 250-417 CFM depending on temperature/humidity.

    Here's the sheet:
    Code:
    		Theoretical max		Grille Size
    Airflow (CFM)	800 cfm			
    ----------------------------------------------------
    M Bed	0.17875	143			8x12
    M Bath	0.02375	19			4x8
    Lvng R	0.39625	317		        14x14
    Kitchen	0.10875	87			6x12
    Br2	0.07875	63			6x12
    Br3	0.16	128			8x12
    Bath2	0.05375	43			4x8
    Total	1	800			596 sq in
    
    Return         800                      18x24  (432 sq in)
    Quote Originally Posted by caslon View Post
    Most know mine and others setup by now. Small 887 ft condo, new ac/furnace.
    The hallway closet right off the living room has a large return cavity below it.
    <snip>
    Replies? Keep in mind my HVAC is in my lap...not down in a basement.
    I've got you beat. Take a look at my setup:


    My air handler's practically in the living room, and the return grille IS in the living room. That return grille is feet away from that B&W 803D speaker. There's barely 1" of clearance around the unit in that makeshift utility closet.

    The entire condo has 12" ceramic tile on a concrete slab. There's large windows on 2 sides of the living room and vaulted ceilings throughout. In other words, an acoustical engineer's nightmare. Even my furnishings aren't helpful -- leather couch, glass & granite tables. All highly reflective surfaces.

    Even with the access panel removed from the wall, the system's inaudible under normal operation. The only way to know it's running is to look at the thermostat or kwh meter. Even the service techs are in disbelief that it's running until they feel the refer lines and feel the vapor line feeling cold, and that's standing right in front of the unit.

    I do all of my audio mastering and mixdown in that room, with the air con running the whole time. The only time the system is even remotely perceptible is when it's running >700 CFMs, which is rare, only happens when the system is recovering from a setback on a dry, hot day and I use 85F as a setback. When I say "perceptible", that's literally the best way to describe it -- you can just barely hear it at the return.

    My brand new $2k fridge is louder and I still hear the ticking of my wrist watch over it, and this is with the system running full-throttle under conditions the system isn't likely to be run under. Invariably the system usually has some humidity removal to contend with, so even on the 2nd stage it's running at < 700 CFM and is quiet enough for me to even record music or do a broadcast in my living room. Numerous broadcasts have been run from the room since the installation of the AC system. All of the supplies remain dead-silent under all conditions.

    I want to note that ALL of this was done without any special sound deadening material. The closet was lined with ductboard, but that's it. On the return, the ductboard is actually reversed (shiny side facing inside the duct) to prevent mold growth below the coil, which actually hurts the acoustical performance of the system. I want to reiterate that this is one of the worst rooms you could design acoustically, yet this is one of the quietest systems the contractor has ever installed.

    Air noise is directly proportional to velocity. The larger the ducts & vents, the slower the air moves and the quieter the system will be. There's no reason why any modern HVAC system should be audible. You want a quiet system? Fix your ductwork and increase the surface area of your supplies and stop farting around with sound deadening material.

    The best way to keep the noise level down in your home is to not create the noise in the first place.

  11. #11
    Join Date
    Mar 2006
    Posts
    254
    So you're telling me exactly nothing. So...you want to jump in on this thread?
    You have a completely silent system...OK....totally silent. Kudos to you.

    Others have seen my pics and understand the limitations of having a small condo with the HVAC closet practically in your lap.

    I don't need to hear you brag, or tell me I need 14x6 type large registers on the wall. I live on one floor upper condo with 2 hot garages below me, large windows and no crawlspace above my living room and bedroom, decently
    insulated. Guess where the heat goes from those garages?

    You telling me I'm a dufus for having gotten a two ton Carrier Slim line 38HDR?
    Rather than a 1.5 ton?

    Take some time and check out the pics that I posted of my condo. Everything you need to make a snap judgement.

    Outta the 4 estimators that came over...all recommended a 2 ton.

    My thread was merely about the problems of having a small tight HVAC closet right off your living room.

    If you want to be MR. Audiophile and tell me you can make my system totally silent as yours...put up $10,000 and I will do the same. Make it a binding bet and I'll pay your airfare over here. Otherwise..bug off.

    It will be interesting how you do attempt and fail to do it, and owe me 10 grand. Mine isn't a full walk in HVAC room...OK?

    I'll take the advice of BeenThere and Dash and others over you. It cools fine and dandy and effeciently. Noise wise...these other repliers know the limitations. It's what it is.

    I'm awaiting untill AUG 22 to get my first months electric bill. From the partial billing cycle from a partial month...it's going to be very reasonable. I learned (as a first time whole house AC user) not to wait untill my unit gets to 81F to start cooling it off. My bad. Keep your core house temp down.

  12. #12
    Join Date
    Feb 2005
    Location
    cincinnati ohio
    Posts
    2,020

    loud air

    My furnace is also in the middle and behind the tv ! I installed a two pipe 95 vari speed last season ! Sealed combustion & two stage is the best for les noise and the vari speed dip switch's helped alot also . I remember 20 yrs ago when it had an oil burner in there Two pipe system pumping that cold oil from an outside tank ... when it hit single digits You talk about noisey
    My avatar is a picture of a Goodman Silencer .....These were commonly used in Goodman country ....Photos by hvac tech ( PaysonHVAC )

  13. #13
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,000
    Quote Originally Posted by caslon View Post
    So you're telling me exactly nothing. So...you want to jump in on this thread?
    You have a completely silent system...OK....totally silent. Kudos to you.

    Others have seen my pics and understand the limitations of having a small condo with the HVAC closet practically in your lap.

    I don't need to hear you brag, or tell me I need 14x6 type large registers on the wall. I live on one floor upper condo with 2 hot garages below me, large windows and no crawlspace above my living room and bedroom, decently
    insulated. Guess where the heat goes from those garages?

    You telling me I'm a dufus for having gotten a two ton Carrier Slim line 38HDR?
    Rather than a 1.5 ton?

    Take some time and check out the pics that I posted of my condo. Everything you need to make a snap judgement.

    Outta the 4 estimators that came over...all recommended a 2 ton.

    My thread was merely about the problems of having a small tight HVAC closet right off your living room.

    If you want to be MR. Audiophile and tell me you can make my system totally silent as yours...put up $10,000 and I will do the same. Make it a binding bet and I'll pay your airfare over here. Otherwise..bug off.

    It will be interesting how you do attempt and fail to do it, and owe me 10 grand. Mine isn't a full walk in HVAC room...OK?

    I'll take the advice of BeenThere and Dash and others over you. It cools fine and dandy and effeciently. Noise wise...the other repliers know the limitations. It's what it is.

    I'm awaiting untill AUG 22 to get my first months electric bill. From the partial billing cycle from a partial month...it's going to be very reasonable. I learned (as a first time whole house AC user) not to wait untill my unit gets to 81F to start cooling it off. My bad. Keep your core house temp down.
    His point...

    Your duct system is undersized. He lives with the same set up but the ducts are sized correctly.

    Get over yourself.
    Perhaps you should have read the instructions before calling.

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