Ducting Return Air

[Burt Alcantara]

Because of noise, vibration, and space I'm moving my ClearVue CV1400 from my shop to either the adjacent furnace room, or the garage.

Garage:The total ducting run minus ducting to machines is 100+ feet. Is that too long? Not sure how to filter the return air.

Furnace room: This requires building a noise containment closet and muffler. We keep a lot of things there. The closet would significantly reduce storage area. On top of that I've already taken up a wall with logs. The advantage is smaller ducting run with filtered return air.

One question about the furnace route. There are 2 entry ways between the shop and furnace. If the return air was in the furnace room would that be sufficient as return air for the shop as well?

I'm open all suggestions on this.

Thanks,
Burt

[Jim O'Dell]

The more duct you have to run, the more resistance there will be. I doubt that it would kill the dust pick up, but it might reduce it some. I'd go to the shortest route possible just to ensure the most air movement possible. I have the CV1800, and my longest run is about 28'. I don't notice a problem with noise, as I wear hearing protection with the tools on anyway. And my shop is a detached building about 25' from the garage. Plus I exhaust outside, and that is where a lot of the noise is. Sounds like a small turbine engine if standing outside the shop.
I eliminated any vibrations by mounting the cyclone on a stand alone stand. It does not touch the walls of the shop at all, so no noise from frequency vibrations on the walls. I also have part of a closet around it that is insulated. Haven't built the door yet.
Hope this helps a little. Jim.

[Burt Alcantara]

Jim,
You say your longest run is 28'. What is the total length of ducting? Or is it 28'?

Burt

[Jeff Duncan]

100' of ducting before you even add your drops wyes etc is going to take away a significant chunk of your collectors suction. I'll leave the numbers to guys better at that sort of thing.
Have you considered leaving the collector where it is now and just building an enclosure around it? I'm not sure I'd want to have the collector right next to a furnace.
JeffD

[Jim Becker]

Since your air return is extremely low pressure and speed, the length of the return is less critical than on the inlet size. In theory, there is no issue bringing it back through your furnace room, but personally, I'd put in an oversize duct directly back to the shop for best results--you can even use large diameter flex duct if you want or channel the air via a joist bay if they run in the correct direction. That also keeps you from pushing potentially dangerous fumes via your air return should something malfunction in the utilities.

I would not move the system to your garage for the reasons stated by other responders. That's too much duct for a small system...the CFM losses from friction would be substantial. (it's not about "suction"...DC systems work at low static pressure and moving volumes of air is what moves the dust and chips) Moving it to an adjacent area or building an enclosure is a better all-around choice.

[Paul Wunder]

Jim O'Dell,

You stated that you installed a CV1800 on a separate stand to avoid noise from vibration. I am also considering the same unit for by basement hobbyist shop. Could you please share how you made the stand, (pics would be great) and how you mounted the cyclone to it. Your assistance would be much appreciated. Thanks.

[Burt Alcantara]

I spoke to Ed Morgano of ClearVue about this problem. He stated that I should not put the DC in the garage because of the run length. I reworked the ducting scheme to pull it back to about 50' +/- and Ed said that would be OK.

Research has unearthed interesting theories about soundproofing. At the moment (subject to change in the same breath), I'm looking at 2 sheets of 5/8" drywall adheared with either Green Glue or the stuff from QuietRock. This laminate will go on the outside and inside of a 2x4 frame room. The inside stuffed with a yet-to-be-determined fill. From what I've read, this should give an STC of about 55+. I realize the STC is a flawed rating but it's something to hang my DC on, so to speak.

What I'm still unsure about is noise from the return air since the main source of noise is from this area. In theory, If I build the above "room," completely enclosed, I should not hear much coming from the room. However, the return air doesn't get out and I'm not sure how the motor would like the confinement. When I had the DC in the shop, I would get a temp rise of about 10 degrees (or that's what it felt like) with the DC running for 45 minutes or more.

My understanding is the worst noise is the exhaust from the impeller. Does that noise travel through the filters and return duct?

Your suggestions and experiences are valued.
Burt

[Ken Fitzgerald]

Burt,

Go to Jim Becker's profile...go to his website and check out how he made his return duct. When looked at from the side, it's shaped kind of like a "Z" IIRC and lined with sound proofing insulation. Sound travels in straight lines and the "Z" reduces that. Lining the return duct with sound proofing insulation, decreases the reflected sound wave.

Good luck!

[Jim Becker]

Ken, it's not in my web site...it's all here at SMC, including in this Workshops Forum from a thread a month or two ago...

[Mick Tuts]

Hello Jim,
I'm a newbie to SMC. I read you posting of 10/11/08 discussing how you built a stand-alone frame for your CV1800 DC. I've just purchased that same unit and am concerned about noise/vibration. Do you have any posted info and/or pics concerning your DC installation. Thanks.
Mick

[Jim O'Dell]

Paul and Mick, the pictures aren't very good, but you can "see" some of it in my shop rehab thread here: http://www.sawmillcreek.org/showthread.php?t=14427&page=2
Starts at post #49. Basically, it is a 3 sided base made out of 4 X 4 material. 3 vertical 2 X 4s at the rear, braced at the bottom to the base, creating an alcove for the cyclone to sit in. The part that the cyclone hangs from is a shelf, also braced back to the 2 X 4s on the sides. In fact, this shelf was made to slide up and down the 2 X 4s. I had screws slightly protruding the braces coming from the front of the shelf back to the uprights. As I walked the motor and shelf up, The braces would "bite" into the verticals so it wouldn't slide back down on me. Think of a telephone lineman climbing up a pole with his belt around the pole, and spikes on his shoes. This allowed me to raise the motor up by myself. Only way to safely do it by yourself. Once in position, just run the screws in the braces into the tree, and also at the shelf into the tree. Very secure. This tree does not touch the closet or building walls at any spot. I used some of the high density foam that my CV was packed with to isolate the stand from the floor, and as a buffer between the tree base and the walls. Works like a charm!! I'll pm you some things I found helpful to have as I started mounting the cyclone. Saves a trip or two (or three!) to the hardware store during the installation. Let me know if you have any questions. Be glad to help. Jim.

ps, Paul, you have a PM also.

[John Schreiber]

In fact, this shelf was made to slide up and down the 2 X 4s. I had screws slightly protruding the braces coming from the front of the shelf back to the uprights. As I walked the motor and shelf up, The braces would "bite" into the verticals so it wouldn't slide back down on me.
Wow that's smart. I never would have come up with that.

[Myk Rian]

The garage idea won't pass code. There is to be NO connection between the house and garage.

[Frank Hagan]

One question about the furnace route. There are 2 entry ways between the shop and furnace. If the return air was in the furnace room would that be sufficient as return air for the shop as well?


By 2 entry ways, do you mean standard sized door ways? Is the shop connected to the furnace room through a hallway with two doors? Or is it two separate openings leading into the furnace room?

There probably isn't a code for this kind of thing, but in HVAC terms, you cannot rely on an opening that can be closed for ventilation air. But, in this case, you can probably use them for getting air back into the shop. Those are big openings.

The thing you want to think about is the effect on the furnace. Does it use room air for combustion (most do, but some have ducting that uses outdoor air). Does it have a powered vent (with a fan) that pushes out the flue gasses, or does it rely on a "regular" vent that allows the flue gasses to float up through a pipe going through the ceiling (a natural convection type of setup)?

Furnaces usually need a room that is "balanced". If you have too much positive pressure, you interfere with combustion, but if you go negative ... then you suck the flue gasses out of that vertical flue pipe and back into your living area in a standard, natural convection appliance, and that can kill you. Its less critical (I think) with a sealed combustion or fan-induced appliance, but its worth checking with the furnace manufacturer's tech department to see (if its a Laars product, I can help; I worked for them for 10 years and still know people there).

[Anthony Smaldone]

There is another way to dampen the exaust noise from the unit. Get a 10' length of that flexable insulated a/c heat duct. Attach it to the exaust port, it will dampen the noise considerably. The larger the diameter the better.
Anthony

[Jim O'Dell]

Wow that's smart. I never would have come up with that.

Thanks John, but if you pick up that motor, then sit and look at it long enough knowing how high it has to end up. You will come up with something that works. I just happen to be chea.....er frugal. :eek: :D:D Jim.

[Burt Alcantara]

Frank,
My furnace is completely sealed with ducting going in and out from and to the roof. At the moment, the return air is going into the furnace room but the sucked air is from the shop only.

The furnace room and shop are essential one large room with a wall down the middle. There are two doorways; one at each end - both without doors.

In the winter it is very hot but very cold in the summer. Have to reverse dress in the shop.

Burt