As The Shop Turns #5: Revised Dust Collection Question

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Blog entry by Natalie posted 05-30-2013 04:24 PM 1607 reads 0 times favorited 3 comments Add to Favorites Watch
« Part 4: Dust Collection What do I really need? Part 5 of As The Shop Turns series no next part

Okay, so my question is not so much about electricity but about suction.

Will 2.5hp provide enough suction to clear the dust from my shop? I will have 8 drops and the lengths of ducting no longer than 20 ft. I will rarely be running more than one tool at a time.


-- Natalie - My mind is like a bad neighborhood, I don't like to go there alone.

3 comments so far

View Grumpymike's profile


2439 posts in 3094 days

#1 posted 05-30-2013 05:18 PM

Hmmm, I’m not an expert but I have been looking into this for my new shop …
You are not giving enough information to give an answer because the HP is not the difinitive answer to cleaning your shop. Air flow is …
It is a combination of the hose size, impeller size, motor size and speed, and add in static pressure and loss in the ducts … Then you will consider the filters and types.
If you just want to clear sawdust, a shop-vac with 2-1/2 inch duct will work if you put blast gates at each machine.
But … If you are talking about fine dust in the air, you are looking at more air volume and finer filtration like .5 micron.
There are several good books available on dust collection at most wood worker supply stores and on line. Each author will have a bit of different slant on the topic, but the basics are all the same.
Do a bit of home work, study, and then decide on which one you want, and go for it … Good luck

-- Grumpy old guy, and lookin' good Doin' it. ... Surprise Az.

View Bluepine38's profile


3387 posts in 3864 days

#2 posted 05-31-2013 02:50 PM

The Bill Thein site with his separators, as well as the Bill Pentz site have way more information than I can absorb
and I have made quite a few visits to both sites to get answers to my questions. The 2.5 HP can also be
misleading, it is true usable horsepower, or just the highest rating they can milk out of their statistics. What
size impeller is being used? Grumpy raised some good questions. Check the online sites first, then when you
have some knowledge, you may decide to buy a good book or two. Hope you have fun in shop. Also you
mentioned electricity. The 1 HP motor on my dust collector is rated at 14 Amps, Harbor Freights 2HP version
is rated at 20 amps, and this is just a start on electricity.

-- As ever, Gus-the 80 yr young apprentice carpenter

View Grumpymike's profile


2439 posts in 3094 days

#3 posted 05-31-2013 03:59 PM

And now that Bluepine has brought up Electricity, ... The advertisers have been playing with our minds again.
There is an old formula that converts amps to Horse Power, Amps times Volts = Watts; Watts divided by 746 = HP.
Now, that being said let’s do some simple math … 14 amps times 115 volts =1610/746=2.158…
How do you get a 1 HP motor to draw 14 amps?? well you get it running and jamb up the drive pulleytill the motor stops and it will draw 14 amps for a moment and then it trips the breaker. So the guys selling us these motors say that it is a 14 amp motor because we tend to buy the bigger numbers.
I went out into the shop this morning and put an ampmeter on my 1 HP sander motor and turned it on. on spinup it spiked at about 10.5 amps and as it came up to speed it settled in at 6 amps draw. Then I put a load on it and it ran the meter up to a bit over 7.8 amp draw or about 1.2 HP.
Confused? yeah, me too. This only proves that the ratings that we see on the sales tags are just that, sales gimiks.
Here is what I have found: The Cubic Feet per Minute (CFM) is the number that we need to pay attention to more that the HP or Amps of the motor. This is a mesurement of how much suction this sucker will suck.
I chose the Grizzly G1029Z2P for my new shop because it gave me the most suck for the buck at 1550 CFM and two 4” inlets to a 6” port. for my new shop that fit the bill and the price was within budget.
Whew, now that I’ve cought my breath, the bottom line here is buy the most suction that you can on your budget.

-- Grumpy old guy, and lookin' good Doin' it. ... Surprise Az.

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