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Forum topic by fivecodys posted 09-29-2016 03:55 PM 608 views 0 times favorited 11 replies Add to Favorites Watch
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fivecodys

581 posts in 1098 days


09-29-2016 03:55 PM

Topic tags/keywords: question

Good morning Fellas.
I am in the process of designing and modifying my DC system.
I am going to use 6” metal duct-work throughout.
I am also going to vent the exhaust directly outside…no filters.
My shop/Garage is not Heated or Cooled and I always work with the door open so no air issues there.
I have read over Bill Pentz articles several times and I didn’t see anything about venting outside.
What concerns me is that there will be very little back pressure since there is not a filter that the blower is trying to force air through. Could this a problem for the blower?
I did a quick little mock up in Sketch-up so you can see what I’m up to.
Your thoughts?

Thanks in advance,

-- Chem, Central California


11 replies so far

View pintodeluxe's profile

pintodeluxe

4853 posts in 2275 days


#1 posted 09-29-2016 04:12 PM

I think it looks great so far. If you do accumulate any dust outside, you could have the duct empty into a plywood box. Any fine dust would settle there, and the air could exit through a hole in the box. A rubbermaid type bin could sit in the box to empty the fines occasionally. This all depends on how efficient your separation is, and you may not need the box at all.

I wonder if the DC motor has the lungs for 6” duct work. From your previous post I am assuming you’re using a 1-1/2 hp Jet DC1100 for the power plant. I think 6” pipe helps tremendously, but usually see it associated with 3+ hp systems. I read a Fine Woodworking article that claimed 1-1/2 hp was the bare minimum to even equip a dust collector with a cyclone/or other type of separator. Their testing as I recall had no long ductwork, just a length of flex hose. Even with that, the airflow numbers were minimal. So I’m imagining adding all that 6” ductwork, and it might be like trying to make a blowgun with a sewer pipe.

At any rate removing the filter from the equation will give you a lot more airflow, and it will not drop off over time (no filter to clog).
Keep us posted.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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pintodeluxe

4853 posts in 2275 days


#2 posted 09-29-2016 04:30 PM

This is what I was imaging for a fine dust catch outside. It could be sized to fit a rubbermaid bin inside the box. A top could have quick-release latches to access the bin.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Fred Hargis's profile

Fred Hargis

3932 posts in 1955 days


#3 posted 09-29-2016 04:35 PM

The only way to know for sure is to measure the amp draw on the motor after it’s set up. I didn’t see the other post, but if you have the 1.5HP jet, no filters might overload it but there are a lot of other things to consider. You say it will be 6” ducting throughout, but if you choke it down to 4” at the tool you move the air 4” will allow. Also, the cyclone introduces a lot of drag that will further reduce airflow….all those airflow reductions will reduce the load on the motor, maybe offsetting the gain from the missing airfilter. So, check the motor label for the full load amps and measure what you really draw. I haven’t been to the Pentz site in a while, but it seems like at one time he did address direct venting out of the DC and generally favored it. Regardless, it’s a great thing to do if the downside issues really aren’t downside issues for you. There will be a small amount of dust that gets out and you’ve already considered the make up air part, so short of motor load you’re good to go.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Redoak49's profile

Redoak49

1944 posts in 1450 days


#4 posted 09-29-2016 08:56 PM

I think it would help to know what cyclone you will be using.

No matter what you should monitor the amps.j

View fivecodys's profile

fivecodys

581 posts in 1098 days


#5 posted 09-29-2016 09:05 PM



I think it would help to know what cyclone you will be using.

No matter what you should monitor the amps.j

- Redoak49

Good point,
I will be using a Super Dust Deputy attached to my JET DC1100 1.5HP Blower motor.

-- Chem, Central California

View Lazyman's profile

Lazyman

688 posts in 849 days


#6 posted 09-29-2016 10:22 PM

if you find that you are overloading the motor because there is not enough resistance or back pressure, maybe you can alwys add some artificial back pressure by restricting the outflow with a blast gate or a reduction?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Nowater's profile

Nowater

11 posts in 1402 days


#7 posted 09-29-2016 10:49 PM

Five feet of straight duct both in front and behind your system will help the cyclone, if you can find room for it. Minimize bends where possible.

I doubt you will over tax your DC, since the cyclone adds an inch or two of static pressure to the system curve and it looks like plenty of ductwork in front of the motor.

View BobAnderton's profile

BobAnderton

219 posts in 2252 days


#8 posted 09-30-2016 02:24 AM

I agree with Nowater. The cyclone adds plenty of static pressure to protect the blower. Using 6” duct instead of 4” duct is the right call to reduce the static pressure loss in the ductwork. It has a tremendous impact. Bill Pentz’s site says that the optimal setup is what you are doing in terms of ducting outside and not having a filter if your situation allows it. There would be a risk if you had a gas water heater or furnace sharing the shop space though. Eventually you’ll turn the DC on without the doors being open.

-- Bob Anderton - Austin, TX - Nova 3000 lathe, Alaskan Mark III mill, Husqavarna Saw

View fivecodys's profile

fivecodys

581 posts in 1098 days


#9 posted 09-30-2016 03:56 PM



if you find that you are overloading the motor because there is not enough resistance or back pressure, maybe you can alwys add some artificial back pressure by restricting the outflow with a blast gate or a reduction?

- Lazyman


That’s a great idea.
Thank you.

-- Chem, Central California

View fivecodys's profile

fivecodys

581 posts in 1098 days


#10 posted 09-30-2016 04:06 PM



I agree with Nowater. The cyclone adds plenty of static pressure to protect the blower. Using 6” duct instead of 4” duct is the right call to reduce the static pressure loss in the ductwork. It has a tremendous impact. Bill Pentz s site says that the optimal setup is what you are doing in terms of ducting outside and not having a filter if your situation allows it. There would be a risk if you had a gas water heater or furnace sharing the shop space though. Eventually you ll turn the DC on without the doors being open.

- BobAnderton


Thanks Bob,
I went back to Bill’s site and I still can find his comments on ducting directly outside. Ratts!
My shop (garage) has two roof vents and a 6”x12” wall vent about 8” above the floor.
This is because it shares the garage space with the gas water heater.
I ALWAYS roll up the big door a foot or so when I’m working to help vent the fine dust particles and fumes out of the garage. I get a nice cross breeze when the man door is cracked a few inches too.
I have taken the issue of the water heater very seriously and I’m extremely careful when using finishes.

I appreciate you comments Bob,
Thank you for responding to my post.

-- Chem, Central California

View fivecodys's profile

fivecodys

581 posts in 1098 days


#11 posted 09-30-2016 04:13 PM



This is what I was imaging for a fine dust catch outside. It could be sized to fit a rubbermaid bin inside the box. A top could have quick-release latches to access the bin.


I was thinking of something similar if the fines create a problem.
My vent will land in the flowerbed that has plenty of vegetation in it and also has about 3” of woodchips to help keep evaporation to a minimum (we are in a drought) I’m hoping that the dust would just settle there and become compost. I will have to see how that goes.
Thank you for you comments.

- pintodeluxe


-- Chem, Central California

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