How much CFM, is too much, on a dust collector?

[Matt Matt]

The title pretty much says it all.

Is there any regulations on speed/CFM/water column , I have search the Bill Pentz website for woodworking and possible combustibles, is there any regulatory governmental restricting on airflow for woodworking machines? Or fire regulations?

I do have a homemade Bill Pentz design cyclone, That pulls about 1800 CFM and 20 inches of water column.

Is too much CFM detrimental?

 

[BukitCase]

For a home shop I don't think there's any real restrictions, altho I'm sure Kalifornica has at least 247 administered by 23 separate agencies...

I'd kill for 1800CFM, I have a 1-1/2 horse Jet collector I added a cyclone to, but it's only 4" pipe out to the tools - seems to work ok, but my particle counter doesn't think so in some cases (older powermatic table saw, I haven't modded the case/base yet for better dust control, some gets by even with an overhead guard running on a separate mini-cycloned shop vac.

If you've digested even 10% of the info on bill's site, you should be able to answer your OWN questions... :=)) Steve

 

[Matt Matt]

I didn’t see where he thought too much was bad. Or was a fire regulation. Mine is a 5hp and 6” pipe.

 

[RVDan]

If it ***** the pilot light out of the furnace and water heater it's too much. Until then you're okay.

 

[Voi]

Is too much CFM detrimental?

Back when I was deciding whether to upgrade or sell off my wood shop I did some reading on Pentz's site and on Sawmill Creek.

As I recall one issue with too much CFM was if chips were not separating from the fines in the cyclone. Some even used three phase motors on their collectors so they could tweak the speed to optimize the separation with a VFD.

I suppose the counter argument to this would be who cares if some chips get through if I'm collecting more dust/fines? As I recall it was thought the filters would last longer and capture more fines if separation was optimized.

Please don't take my word for this. I did decide to liquidate my shop and I never did set up a DC system. I would Google [VFD dust collector] without the brackets and see if that leads you to any information. My memory may be completely backwards.

 

[Jackfre]

I wouldn't worry about it. Watch and see how it does and back it off as necessary. You can probably do that with smaller tubing sizes. If however you are at a machine and your hair pulls towards the saw blade it probably is to much.
Bukitcase, I had a '48 Unisaw that I converted with dust collection. I added 4" fitting (That piece is available from Rockler or Woodcraft) to the lower back and took 3 pcs of 1/4" tempered hard board applied to the base. the center piece was a ramp to the DC inlet pipe. The other two pieces channeled the dust onto that center board from each side. A high taper is good there. I also made a ventilated motor cover, as the original was long gone. I took foam pipe insulation and packed it between the cabinet and table top. It worked really well. The blade still carries a lot of dust which it throws at you, but you can moderate that by slowing your feed rate to allow the air flow to have a chance to pull the dust. You will be happy you spent the time on this.

 

[strutaeng]

If your shop is not heated or cooled, I don't see a problem. I assume you leave a door open or have some sort of vent to let air inside, right?

 

[R. Deschain]

I wish I had that sort of "problem." Sort of like having too much money, a wife that is too pretty, kids that are uber successful, and a huge pecker...

 

[Git]

I have a 3hp JDS Dust Collector that advertises 2,300 CFM
http://jdstools.com/product/3hp-cyclone-3100-ck/

Keep in mind, even if that number is accurate, by the time you account for parasitic losses - length of ducting, 90 degree turns, etc etc, the actual cfm at the machine is going to be far less

 

[6768rogues]

If it can **** a dead cat through a 4 inch hose back it off just a little bit.

 

[Texsun]

Mine is 1650 cfm and the only "issue" I've had is occasionally a piece of wood will get "stuck" on the router table due to suction. If I open another machine's blast gate a little, no more problem.

 

[BukitCase]

Jackfre, thanks for that; mine's a PM66 that was made BEFORE the employees found out their jobs were getting exported - it runs so true it's scary, and so smooth I can actually balance a nickel on the table with it running and it just sits there - your description sounds EXACTLY like what I'm planning on; already got the rear dust connector removed, need to make a blocking plate. Also have the low, under-the-table extension port in place, just need to figure out the best way to fab the "chute" pieces with all the stuff in the way, and fab up a replacement motor cover (missing like yours) - I've gotta relocate several stacks of wood OUT of the shop and into a shipping container so I'll have room to set up the REST of my woodworking tools with enough elbow room for good infeed/outfeed paths.

If I LIVE long enough, I might actually get to MAKE something in the shop after getting it set up :=))... Steve

 

[jgorm]

Over 15,000 cfm is too much.

 

[BukitCase]

Maybe not, if your ductwork's big enough - it's actually the VELOCITY that's important, IIRC it should be around 120 mph - so if you needed that speed with, say 24" ductwork it'd take 16 TIMES as much CFM as it would with 6" ducting, or 28,800 CFM.

And yeah, not likely in a home wood shop; but the place I worked before retiring a few year ago had cyclones with 36" ducting and 100 horse motors, so it ain't science fiction :=) Steve