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Originally Posted by ProperVenting

Gosh, this is devastating all the way from 3000 to 2000 CFM and u still insist to further attenuate the run by putting (2) 90degrees elbows, hence further increasing resistance?

I was allowing for those ells.

If you want 3,000 CFM, then you need to have a fan that can move 3,000 CFM at a static of .5". But that isn't what you bought.

Originally Posted by energy star

Dwyer Instruments will help you. This may not be an off the shelf item (It may be, don't know) I have installed many Greenheck fans, nice stuff.

I checked the Dwyer Instruments, Inc. WEB site, - they are specializing mostly in flow control & other related categories. I didn't see any fans on their site. Maybe they can refer me to proper mnufactures if I call them

Dwyer Instruments will help you. This may not be an off the shelf item (It may be, don't know) I will look into this deeper. The "control section" area of this forum may be a better place to get some help. But, like I said, I'll look around for you.

I have installed many Greenheck fans, nice stuff.

Originally Posted by ProperVenting

Very smart and sensible suggestion, indeed. The real question is, - are they produced / manufactured here in USA / Japan or Europe? So far, I saw only constant speed varieties from guys like Soler / Fantech, Greenheck..etc. I flatly refuse to buy anything from China, especially mechanical devices requiring high quality bearings and other hi quality important components.

Hmm... after I posted I found That Greenheck actually makes one for Lab ventilation purposes, BTW, this is a link. Anything else I missed?

Originally Posted by beenthere

Probably get between 20000 and 2400 CFM.

Gosh, this is devastating all the way from 3000 to 2000 CFM and u still insist to further attenuate the run by putting (2) 90degrees elbows, hence further increasing resistance?

Originally Posted by thermofridge

What is wrong with one central location? How do you know they are not powerful enough? What happens with your design when some bedroom windows are closed? Where will it suck the additional cfm from? I am as confused as you. I have installed many of these and they are very quiet. I was trying to help by giving you an option. I did not think I was being anything but helpful. Good luck.

First of all, my sincere apologies if you sensed or felt that I was rude toward you; nothing of that sort of behavior was intended. Secondly, in my current design it will never happen because WHF fan will be turned on only manually after remote humidity and temp sensors will alert / notify my computer that conditions are right to turn WHF on and all windows will be opened. I know what you are going to tell me, - if nobody is there to open windows, fan will never be turned on and I'll be clearly wasting a perfect opportunity to cool the house with cool outside air. Well seems like a better alternative to anything else.

Of course, there is always another option, like for instance, forget all about stupid windows and build a closed loop system drawing air from inside and supplying it from outside through huge supply vent. In this case I can go fully automatic and I will never depend on open/closed windows in my life. Are you catching my drift?

Originally Posted by energy star

What you need is a VFD exhaust fan with a building static sensing device that will increase / decrease fan speed (cfm) with sensed restrictive pressure.

Very smart and sensible suggestion, indeed. The real question is, - are they produced / manufactured here in USA / Japan or Europe? So far, I saw only constant speed varieties from guys like Soler / Fantech, Greenheck..etc. I flatly refuse to buy anything from China, especially mechanical devices requiring high quality bearings and other hi quality important components.

What you need is a VFD exhaust fan with a building static sensing device that will increase / decrease fan speed (cfm) with sensed restrictive pressure.

Originally Posted by ProperVenting

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??!!

What is wrong with one central location? How do you know they are not powerful enough? What happens with your design when some bedroom windows are closed? Where will it suck the additional cfm from? I am as confused as you. I have installed many of these and they are very quiet. I was trying to help by giving you an option. I did not think I was being anything but helpful. Good luck.

Originally Posted by JBM1000

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.

I'm having trouble visualizing this. Could you provide a diagram? I find this very interesting because I think sound is too often overlooked in design. I especially dislike a loud HVAC system in a setting that suppose to be relaxing, like restaurants.

Probably get between 20000 and 2400 CFM.

Originally Posted by beenthere

What ESP/static is it rated to work against. it should list CFM at several different statics.

TIA and there u go, hopefully it will give u some ideas, this is FKD-16 variety

What ESP/static is it rated to work against. it should list CFM at several different statics.

Originally Posted by beenthere

Probably gonna need to be bigger then what you would normally run so as to keep grille noise down.

It just dawned on me that my 3000 cfm inline blower may not be powerful enough to pull air out through newly built ventilation network for 6-8 rooms. This is way over my head and I am afraid that I just wasted great deal of money on my blower and would have to buy a bigger one. Plz, tell me that I am wrong and that blower would be sufficient.

Probably gonna need to be bigger then what you would normally run so as to keep grille noise down.

Originally Posted by beenthere

Yep, it would take 2-18".

I don't need to oversize individual rooms, right. CanI go with regular specs? With the exception of running sound proof flex line last 6 feet to the register?

Originally Posted by beenthere

Yep, it would take 2-18".

Thanks, much appreciated

Yep, it would take 2-18".

Originally Posted by ProperVenting

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

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?

Originally Posted by beenthere

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.

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