DC outside venting through the roof

[Adam Strong]

I am finally back to getting the shop re-arranged. I have a JDS 1.5HP DC I am running through a Thein Separator and going to vent out the roof of my shop. Though easier to go through the wall, I already had planned to mount the blower on the wall (concrete block) with an isolation pad, and going through the roof should help keep the next door neighbor a little further out of ear-shot of the outlet. I plan to use 8-10' insulated flexible 8" HVAC to go from the 5" DC outlet to the roof vent to work as a muffler (per Bill Pentz's site). Has anyone else done this? What type of roof vent should I use, either a Chimney type or a range hood type? Would either cause any problem with back pressure?

I am not plumbing the shop. I want to have the DC separator be stationary in the corner of the shop and plan to use the Dust Right hose to use one machine at a time. This will save the footprint of the JDS mobile base. With a 2 car garage shop that still houses a car, the shop is on wheels and the machines can be moved to keep from having a long duct length to the DC.

[Alan Schaffter]

Venting through the roof is fine, in fact better than using a filter, but are you going to have a J top or raincap? A large radius 90+ turn- something slightly more than a 90, but less than 180 would keep out the rain and offer the least resistance. I wouldn't use flex unless it has a smooth interior, free of ribs. Resistance to flow whether on the DC intake or exhaust is still resistance to overall system flow.

Also, how far do you plan to run the Dustright hose? That is 4" (or less?) ribbed, flex hose which is ok for shopvac type use, but about the worst combination for good CFM. The only thing worse for machine dust collection with that blower would be 3" or smaller flex. You would be better off running a smooth, hard duct to a central location where you can then attach a much shorter length of 6" or 4" flex to run to each machine.

[Adam Strong]

As far as J-top or rain cap, that was my question, I just wasn't sure what they were called. The range hood vent type is a J-top and the chimney type has a rain cap. As for the HVAC flex, this was recommended on Bill's website to act as a muffler (more efficient and cost effective than the glass-pack type). I was also thinking that going from 5" DC outlet to 8" flex would make up for any resistance in the flex which will be a long sweeping radius to the roof vent. The dust right hose is 4" diameter and will in most cases be 10' or less from the separator. The separator has a 4" inlet and 6" out to the 6" intake on the DC. I have considered making a 4" outlet to the DC which has the "Y" taking the 6" port into two 4" ports. -OR- Making the inlet on the separator 6" and just using 6" flex to the machines without the Dust Right hose, but that requires modifying the 4" outlet on the machines to 6".

The DC will be about 5' above the separator, using 6" sheet metal HVAC duct, with 1' or so of flex connecting the separator to the metal duct and 6" or less connecting the duct to the DC. I do hope to upgrade to a 2-3hp unit in the distant future, but for now I am trying to get the best with what I have. I know that losing the 1 micron filter and bag will help with airflow and hope to at least offset the loss thru the ducting.

[Alan Schaffter]

I missed the outlet being 5". As long as you keep the flex straight (up) and relatively short, 8" should be fine.

I couldn't quite follow, did you say something about putting a 4" wye, on the intake to the blower? If so, DON'T do it!!!! Use a 6" flange. 1.5 hp and the likely size of that impeller are already on the low side so keep all runs as straight and short as possible, minimize bends, avoid 90's, especially tight ones, keep the use of flex to a minimum.

Again, think about hard duct running from your separator along the ceiling to the center of your shop, then a gentle 90 connected to another length of hard duct via a flexible coupling (piece of truck tire inner tube and two band clamps). The second length would hang down like a refueling boom on a KC-135 Air Force tanker aircraft. It would be able to swing around so you can connect it to your machines with a very short length of flex, or pivot it up parallel to the ceiling and out of the way when not in use or when you need to move a project, tool, or sweep up.

[Chip Lindley]

Consider the "mess" that will accumulate on your roof (and in any gutters) due to rain or snow over a period of time! It's a fine dust, but it is still exhausted, especially when your bin is full!

Attaching wire mesh over the exhaust is a must, to keep out all varmits; same as a stove flue.

[Adam Strong]

I couldn't quite follow, did you say something about putting a 4" wye, on the intake to the blower? If so, DON'T do it!!!! Use a 6" flange.

The wye is the one that came on the blower from JDS, as is configured now with the separator, I am not using it.

Consider the "mess" that will accumulate on your roof (and in any gutters) due to rain or snow over a period of time! It's a fine dust, but it is still exhausted, especially when your bin is full!

Attaching wire mesh over the exhaust is a must, to keep out all varmits; same as a stove flue.

I have thought about the mess on the roof and it is a disadvantage of going thru the roof vs. the wall. The good thing is that here in FL I get up on the roof and wash every now and then as it is, with the humidity here, mildew is a problem. Anyway, if it were not for the neighbors, I would not hesitate to go thru the wall, it would be shorter ducting, no need to muffle, and an all around better setup.

The J-top I bought yesterday already has the mesh installed so nothing of any concern can get in and set up camp.

Thanks for the help guys, I plan to get started this weekend once I get the new electrical ran. I am also installing a shop air cleaner to help as well, look forward to breathing a bit easier and less dust in the shop.

[Adam Strong]

I finished installing the DC venting thru the roof today. I am very happy with how it turned out. The noise outside is not bad at all, standing next to the neighbors house there is only a low hum.

[Alan Schaffter]

Ya gotta love it when a plan comes together! Now finish hooking everything up and make some serious sawdust!!

[Van Huskey]

Glad it worked out, gave me some things to consider!

[ray hampton]

The wye is the one that came on the blower from JDS, as is configured now with the separator, I am not using it.




I have thought about the mess on the roof and it is a disadvantage of going thru the roof vs. the wall. The good thing is that here in FL I get up on the roof and wash every now and then as it is, with the humidity here, mildew is a problem. Anyway, if it were not for the neighbors, I would not hesitate to go thru the wall, it would be shorter ducting, no need to muffle, and an all around better setup.

The J-top I bought yesterday already has the mesh installed so nothing of any concern can get in and set up camp.

Thanks for the help guys, I plan to get started this weekend once I get the new electrical ran. I am also installing a shop air cleaner to help as well, look forward to breathing a bit easier and less dust in the shop.

Washing the roof will help UNLESS THE WATER DRAIN INTO A PIPE

[Adam Strong]

Another new thread brought me back to this one and I thought I'd post how it is all working out. After nearly 3 months with this setup, using the DC a few times a week, I don't notice any dust accumulation at all on the roof. The rain seems to take care of what little may stick. Everything works great and I have found no drawbacks to this system. As before, the Thein style barrel takes care of all but the finest particles and no chips are sent out to the roof. If you are considering doing this, don't hesitate to give it a try... it works GREAT!

[Karl Wittnebel]

I am venting a cyclone out through the roof. Would like to use 8" pipe. I do not want to use a conventional HVAC roof cap, as they all seem very flow restrictive.

I would like to use a section of straight 8" steel pipe up through the roof, with a rain cap on it like for diesel generator exhaust. It seems like the least restrictive solution. I do not want a big J up on my garage roof. I figure if I put it up a few feet that should keep all but the most dedicated critters out, but could use expanded metal inside the pipe also to be sure.

I have two questions:

1. does anyone know how to flash a straight pipe (no flange) into a sloped, built-up roof? Alternatively, does anyone sell 8" pipe section with a roof flange on it?

2. Can anyone think of any other reason not to do this? I am trying to keep the noise down for the neighbors and this seems the most straightforward solution. Any building code considerations? The cyclone is up near the ceiling, vents through the ceiling via 8" flex duct to attic then out roof. Cyclone intake is 6" from 3hp 6" fan, running 6" all the way to CNC router table.

Thanks

[Alan Schaffter]

I see no problem. Just get a 8" standard slip on angled roof flange with rubber gasket or without gasket (will need to be sealed) should be fine. You may need to use a wood stove fitting. A google search will yield many styles for all types of roof penetrations.

You will need to dig a bit deeper for a vent top flapper cap and may even need or want to fabricate your own.

[ray hampton]

I am not a roofer expert but think that you need to know the pitch of your roof in order to buy a flange that will seal the roof hole around the pipe, I believe that the flange go next to the roof then a sheet metal with a hole cut in it go over the flange

[Chris Parks]

[QUOTE=Karl Wittnebel;1804534
I would like to use a section of straight 8" steel pipe up through the roof, with a rain cap on it like for diesel generator exhaust. [/QUOTE]

I would think that keeping the flap open using air flow would be restrictive. Just guessing here of course, someone may know better.