ReplyUse 26" pipe off of the fan and at least 2 90s to reduce mechanical noise.
Regular Guest
Hmm..looks really promising and almost exactly what the doctor ordered. Will give them a call on Monday. Thanks a lot.Originally Posted by chrisevansac
God Speed, Jim. We'll miss you - 2-26-23
Use 26" pipe off of the fan and at least 2 90s to reduce mechanical noise.
Regular Guest
With your credentials, I have to take your opinion as a gospel or how it is defined in math as a lemma, however with all due respect I have to ask you this:
1. First of all, are you talking about flex pipe? Does it even exist in this size? Frankly speaking, I thought that going from nominal 16“ to 20” was already overkill so you put completely different prospective on my project and I really appreciate that.
2. Secondly, I assume that 2 90’s will slow down air velocity even more and therefore will further reduce the aerodynamic noise.
3. What size and kind of pipes you suggest to use for each bedroom / bathroom (they are all different sizes). Originally, I thought that for the simplicity sake, I would bring 8” pipe and install one 8” round intake grill regardless of the room size. Am I right about that? Somehow, after I read your opinion, I have a nagging feeling that I am totally wrong.
4. And finally what about the idea of using special sound insulating jackets on a motor?
God Speed, Jim. We'll miss you - 2-26-23
I was talking metal pipe. Flex over 20" is not standard in most areas. I'd run flex or sound attenuated duct(last 6 foot) to the individual grilles. Grilles have to be sized for the room they'll be serving and so must the duct be sized for the room.
You could also run duct board as the main trunk line. Duct board has sound absorbing properties. 2 90s in it would still help reduce noise even more.
Small duct work makes for loud air movement noise.
Regular Guest
Thanks again for the words of professional wisdom. I am wondering if I can step down to 24" round because that is the largest diameter available in flex pipe, everything else above is custom sizes. Also is there a direct equal relationship between sq. area of round duct and rectangular one?
I know that prices are not permitted here but can you at least give me an idea on the difference between all these materials, so I know where to spend most of my time.
Professional Member*
Having have done some recording studio's, if you have the $ one can create sound isolation by breaking the sine wave of sound and cancelling up to 80% using two methods without losing more than 10% CFM and FPM. at each branch run make a canvas break from round into equivalent duct board with internal 33 degree angled baffling that is up to 1/2 height x 3 into output canvas break again and back into final 5 ft hard pipe or flex at that point. The factoring is outside the box thinking and if sound waves cannot stay in sync with the air at any velocity then "Energy Itself Must Transfer" theory. The duct board and canvas become a heat sink in theory from the fibers of both canvas break and duct board vibrating removing the sound energy.
Take a metal pipe suspended like a wind chime tube and tap it with a metal screwdriver, it rings loudly. now just hold it with your hand and tap it, now it barely has a thud to it. (Do not even ask about related harmonic coupling). Apply that process to your design.
God Speed, Jim. We'll miss you - 2-26-23
24" will work. You still want it to make 2 90° bends. Velocity is up a bit, but should be ok.
Best to just call around and get the actual prices to know what the difference will be.
Professional Member*
Have you considered using multiple smaller fans, one for each room?
Regular Guest
Yeep, please check it out here
Professional Member*
If your objective is to save on AC costs during mild weather you have a VERY long payback time...
Professional Member
I have a whole house fan and it keeps the first and second floor pretty comfortable when outside temps are at 85 degrees. Above that ac goes on. You can either trim your doors or put back to back ra grills above the doors. This will be alot cheaper and easier than ducting each room imo.Because I do not believe in this solution as it implies that there is 1 (One!!) central location from where it is pulling all air. They are not powerful enuf and what happens when all bedrooms doors are closed. Where it will suck the air from??!!
Regular Guest
Hmm..what fan are you talking about? What about noise level?
Professional Member
I don't know the brand it was here when I bought the house. Its noisy as hell when I start it up but after that its not too bad. My electric bill in the summer is around $75. I can get used to a lil noise. I can't get used to 200 electric bills. Not until I win the powerball lottery
Professional Member*
With the price of sheet metal and fab work, metal prefab duct, flex duct, duct board and/or canvas connectors at the sizes you are talking about you will be looking at a looooooooooong payback period versus running the ac in mild weather. Not to mention the cost of the fan itself and other materials (grills/registers, tape, mastic etc.) to install it and time to install.
Regular Guest
Aren't we presumptuous again??!! You have no clue who I am and what my connections and capabilities are. Despite the fact that you are in a business, I can probably buy everything that you buy and pay 40-70% of what you are paying, in some cases even less. I would never hire you to do the job @ the rate you are currently charging your poor customers. How that grabs you, braggart? Seems like I have to place you immediately on my ignore list and that is where you belong as far as I am concerned. Keep up guessing.
Professional Member*
I'm assuming you are doing the work yourself, and still you are talking about a good amount of time and money for little gain.
Regular Guest
Can I split the main trunk in 2 trunks of 12" each and distribute evenly the rest of space between them? I realise that I still have to do 90 bends. TIA
Regular Guest
Sorry for bothering you with this stupid question, should have thought about that before asking as there is no mathemetical correlation and 2 12' pipes won't be even close to what I need. I guess, I need, at least 2 18" trunks, right?
God Speed, Jim. We'll miss you - 2-26-23
Yep, it would take 2-18".
Regular Guest
Thanks, much appreciated
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