Looking at installing a outside air dump for DC

[Jim Andrew]

Thinking of putting a T on the air discharge of the cyclone, and sending the air outside, using a blast gate to change to the filter. Do I need more than one blast gate, thinking if I put the gate on the exterior dump, the resistance from the filter will push the air outside. Then just close the blast gate to use the filter to return the air to the shop. Was considering building my own air dump on the exterior, There is a 2' overhang on my soffit, and if I just close it up to the top, there should be no moisture introduced to the vent. Was going to use wood to make the dump, as I am a woodworker. Any comments?

[William C Rogers]

I don't have an answer to you gate question other than it makes sense. I was going to do the same thing at one time, but set it up to vent outside to try. I realized I didn't need to have the filters and vent outside 100% of the time. I put a blast gate on the interior wall just where the vent exits to shut off ( eliminates any moisture ). Regarding heat, I have in floor radiant heat. I can run the DC for hours and not really affect the shop temperature more than maybe 1 degree. My makeup air is from my gable vents. I am using the EBay cyclone and even running the drum sander there is nothing to cleanup outside. If you can vent outside, do it. One of the best things I have done regarding dust collection.

[Robert Delhommer Sr]

Sounds good to me. The air would take the path of least resistance, a little bit may go through the filter. I personally just exhaust the air outside and don't have any filter at all, works well for me.

[Marty Tippin]

The air will go where it has the least resistance. But if that's the choice between going straight into the filter and making a hard 90 degree turn to go outside, I don't know which one will win. Depends a lot on the backpressure from your filter I suppose.

<Insert standard reply about the need for make-up air here> - I assume you've anticipated that already and have a solution in mind. If not, some forum searching is probably in order...

[Jim Andrew]

As far as make-up air is concerned, I have 3 overhead doors in the shop. The leakage from the doors should suffice.

[Dan Friedrichs]

Can't hurt to try. Worst case, you have to add a second blast gate. Since you already own the filter, there is some advantage to being able to switch between outside and filter, but once the filter fouls, I'd suggest just permanently venting outside. Cost of a new filter likely exceeds any savings on heating.

Make sure your vent to outside has gentle curves (Y's, not T's) and large diameter, unobstructed paths. Since it's under pressure, you needn't use PVC or metal ducting - you could also use something like flexible insulated HVAC ductwork, if that's more convenient.

[Jim Andrew]

I made the blast gate from plywood, and the outside dump valve also from plywood. Just used a 3 1/2" door hinge mounted at the back side of the plywood and it shuts well. Hope the air discharge will push it all the way open. I plan to put a T in place of the elbow on the discharge so I can go straight out through the wall.

[James Biddle]

I talked about this with an Oneida rep yesterday. His view was that the filters lasted so long in a correctly designed system, there was little benefit to having both filter and outside air option. Pick either one. We're opting to dump directly outside without filters.

[Jim Dwight]

The filter may last a long time but it won't stay clean a long time, at least without a cyclone in front of it. If I put a DC in the new shop it will have a cyclone and dump outside, no filter. I've already wasted too much time cleaning a cartridge filter.

[Mike Hollingsworth]

I talked about this with an Oneida rep yesterday. His view was that the filters lasted so long in a correctly designed system

that is unless one forgets to empty the sawdust can and all heck breaks loose

[Rick Potter]

Or if one has a drum sander. I cleaned my filter once, then vented outside. No evidence outside of any problem. Onieda told me the filter would clog fairly soon when using a drum sander.

They were right.

[Bob Grier]

I really don't think it needs to be stated but I will because of safety. In certain situations, like mine, where there are combustible appliances such as gas furnace or hot water heater in the same space or connected space as the dust collector, then to avoid downdraft in the appliance combustion chamber and potentially carbon monoxide buildup in the shop, a makeup air system can be installed. The sensor goes in the exit duct of the dust collector and when it sensed pressure, as when the dust collector turns on, the makeup air damper opens and lets return air enter the space. The system is simply a pressure sensor, transformer, and electrically operated damper. I guess an easy way to determine if you are creating negative pressure in the room when running the dust collector is to slightly crack open a door to adjacent space or outdoors and then turn on the dust collector and see if it moves the slightly open door. If it does, you may not have enough air leakage into the space. Best to just measure with instrument to determine if makeup air is needed. The way I do it is to just open a window or door when I operate big exhaust fan like in large cooking exhaust fan or dust collector. Google "makeup air" for different systems. They come as complete system, are simple and not expensive.

[Rick Potter]

Bob is right. Although I have no appliances to worry about, I do need to open a door or window. If I don't, the 3 HP Oneida in my shop will starve for air. The way I noticed this was when my RAS dust was noticeably worse. I walked to the door and opened it...wham! The door opened so fast it pulled the knob from my hand and would have slapped me in the face if my foot hadn't stopped it. No exaggeration.

[Jebediah Eckert]

Bob is right. Although I have no appliances to worry about, I do need to open a door or window. If I don't, the 3 HP Oneida in my shop will starve for air. The way I noticed this was when my RAS dust was noticeably worse. I walked to the door and opened it...wham! The door opened so fast it pulled the knob from my hand and would have slapped me in the face if my foot hadn't stopped it. No exaggeration.

Rick, you may have already mentioned it but are you venting outside, or is that when you ran a filter? It's all confusing to me and I only care enough to learn the minimum to get it done. Oneida wasn't all that familiar with what I need. I have a wood stove in the basement and am worried about pulling smoke out. I want to outside vent most of the year and run the filter during the winter. They said running with a filter shouldn't be a problem with wood stove, but it wasn't too convincing. I studied up on the heat loss, make up air etc etc so I think being able to switch is the way to go. It doesn't have to be all that convenient because it only has to be done when I start the wood stove (actually a wood boiler but same idea), then when I run out of wood on March or so. That's my thought anyway.

I would buy a cheaper unit and just blow everything outside, chips and all. The problem is once winter hits and the snow gets deep it would be hard to empty, if not impossible. Although if I made a decent sidze box it would last a bunch. I have a tractor to pick it up. Thinking out loud if it did fill up, and there was deep snow I could always just open up the pipe and blast it onto the snow until the spring.

[Bob Grier]

Makeup air replaces the air pumped out of the room or out of the connected space. A dust collector discharging outside or a paint station exhaust fan discharging outside can cause negative pressure in the shop space if not enough leakage or makeup air is supplied.

[Jim Andrew]

I have Grizzly's small widebelt sander, and my filter plugs fairly quickly when running the sander. That is the reason for this change.

[Rick Potter]

Jeb,

I vent outside. See post #11.