Thread: Questions on DC and Bill Pentz cyclone.

i have the DC7.

I'm sure bob will explain this all better then me but....

the DC3 and DC7 have the same sized impellers, and as you said you only getting a bigger 3HP motor, what you have to remember both those motors are still spinning at the same speed and so are moving the same air flow. The only real advantage a DC7 has over a DC3 is the larger outlet bag capacity (having two instead of 1 allows for less restriction on the back end). the 3hp motor will just let you run higher currents for longer, but it doesn't let you move any more air then the DC3.

If you're looking to upgrade you're better off finding a 3 phase 3HP motor and run a VFD on it (so it will work off single phase) this will also let you up the Hz from 50 to 60 which will spin the motor faster, which spins the impeller faster which moves more air. I think its something like 20% more air going through it.

also i still think 90% of the chinese ebay knock off motors are the exact same HP rated motor with just different/fake build plates.

With the DC7 you get two filters and two bags so
- you only have to empty the bins half as often.
- the twin filters is less restrictive so more flow - at least while they are not clogged..

The improvement in flow depends on the bags.
A so called 5 micron clean filter drops reduces flow by 12% of slow so two bags drops 6%.
A BP cyclone on a 3HP ,12" impeller will drop flow by about 25% - in other words not recommended
On a 4HP/15" BP impeller the loss is ~16% but this has so much grunt anyway it can afford to lose plenty and it will still suck.

In practice the most air you can get through a short 6" duct is ~1250 CFM.
In practice its nice to have about 1000 CFM available through the bigger machines.
To generate this you need a minimum of 3HP and a 13/14" impeller, short ducting runs, and minimum junctions, and do not put a cyclone on it.
But do consider a 3 Phase and put a VFD on it. 60Hz will give you 20% more flow,

Don't forget that most machines have ports that are usually the most restrictive part of DC so unless these are attended to the rest is bit of a waste of time.

I wouldn't go to the expense of a new motor unless you do as haveabeer69 suggests. The only thing a bigger motor will do is give you longer motor life. Blower performance depends upon motor RPM not power rating. The blower determines the torque demand and thus the power requirement. Try it first with the original motor. If it fails sooner than you like only then replace it with the bigger one.

For a different way of looking at flow differences:

Removing all of the stuff on the outlet of the blower decreases pressure loss by the equivalent of about 71 m of 150 mm PVC duct. The only information I've been able to find for the Pentz cyclone on pressure drop is his duct estimating spreadsheet. It seems to imply 2" at 1000 CFM. That's probably for the 18" body but It's not really specified. Assuming that is correct then, including a 9" to 6" contraction on the outlet, that would be the equivalent of about 21 m of 150 mm PVC.

The DC7 with two separator rings would have the equivalent of about 18 m of 6" on it's outlet so, depending on what you do with the fan outlet, a modified DC3 with cyclone could be fairly close to a DC7 in performance.

Also, a square law curve fit to that fan shows an internal resistance equivalent to about 28 m of 150 mm PVC. You can use that to compare relative flows. Just don't forget to take the square root of the ratios and include whatever is on the inlet.

Welcome to the forum Marty.

If you haven't already read it there is a Sticky at the top of this part of the forum on The Generic 2hp DC, showing how to modify the impeller housing for improved flow. If you are staying with your existing DC, even with upgrading to a 3hp motor, make the modifications.

You haven't said whether you are in an area where you can exhaust straight outside or not. If you can you remove all the resistance/drag on the downstream side of the DC. Even better is to locate it outside in its own shelter either with or without the bags to reduce the noise and dust leaks into the shop.

If you must keep it inside then upgrading to cartridges will up the flow a little.

You mentioned adding a Pentz Cyclone but didn't say if you were making it or buying just the cyclone from the Clear Vue dealer. Bill says in his site that a 3hp (doesn't mention the impeller size) should be 20" in diameter and a 2hp should be 22" across. So if you are making your own and not planing on upgrading to a 4hp or 5hp 15" or 16" impeller then you should make the cyclone to suit what you are using for best efficiency. If you do have plans of upgrading to larger then making one to work best with the biggest motor makes sense accepting slightly less efficiency for the time being. If you are buying the cyclone only from the dealer the same holds true. Using a cyclone will let you exhaust to the outside without filters which offsets some of the cyclone resistance.

Using a 3 phase motor as already suggested will give you the 20% increase in flow. They are, at least here, a little cheaper than a single phase motor which offsets the Variable Frequency Drive (converts single phase to three phase) cost. There are good ones made in China that are not wallet exploders. Two other benefits to the VFD not mentioned. First is it can be programmed to limit the inrush of current reducing the current demand on startup. The second being able to stop and start the DC more frequently. This is because of the first benefit which reduces the heat buildup in the motor. A single phase motor can get hot if started and stopped too often.

Pete

This really is a rabbit hole eh?
Thanks everyone for the replies


Curious as to what VFD you would recommend for the 5hp motor found on the DC-90 etc A link to one would be good so I can make sure I'm looking at the right things.

By the time I get a 5hp motor, VFD, 14" fan etc, it's getting expensive. And I still have to build the cyclone.

I'm now thinking a better option would be to open up the inflow and outflow on the DC3 (bore it out s to speak) and make a Thien separator, and vent what gets through outside, or inside through one of those pleated filter canisters (which I already have)
I don't make a lot of chips, and the main issue with a Thien is letting the bin go over 1/3 full I believe. They don't separate as good as building a Bill Pentz cyclone, but neither would a cyclone on a "bored out" DC3 as its only got a 12" fan on it going by what you all tell me.

Thoughts?

My system is a fully modified 2hp system as per the sticky. I am running a long duct though.
It goes into a standard separator ring with a pleated filter but has another 5” duct off the separator going to a Thein filter. This is because a single pleated filter couldnt handle the airflow after the mods ie. it was too restrictive.

Here’s some info from one of my earlier posts with measured air flow

”Just decided to measure my system. It’s described in Post #17.

The system measured is basically 6 metres of 150mm PVC pipe and 3 metres of Flexi going to a table saw.

All hooked up - 620.4 cfm

Thein filter hose disconnected - 649.8 cfm so it’s pipe is pumping straight to the air.

Outlet pipe from the impellor disconnected from separator ring and pleated filter so pumping straight to air - no filters. - 720.9 cfm”

Originally Posted by Arty Marty

This really is a rabbit hole eh?
Thanks everyone for the replies


Curious as to what VFD you would recommend for the 5hp motor found on the DC-90 etc A link to one would be good so I can make sure I'm looking at the right things.

By the time I get a 5hp motor, VFD, 14" fan etc, it's getting expensive. And I still have to build the cyclone.

I'm now thinking a better option would be to open up the inflow and outflow on the DC3 (bore it out s to speak) and make a Thien separator, and vent what gets through outside, or inside through one of those pleated filter canisters (which I already have)
I don't make a lot of chips, and the main issue with a Thien is letting the bin go over 1/3 full I believe. They don't separate as good as building a Bill Pentz cyclone, but neither would a cyclone on a "bored out" DC3 as its only got a 12" fan on it going by what you all tell me.

Thoughts?

Yup it is a 4 lane rabbit hole! And that bunny can sure move.

Clearvueoz supplies their machines with a Powtran VFD VFD | Clearvueoz.com.au It is the P19000 series and would be the one to consider. They have done all the looking for you. The one I ordered via Alibaba from Powtran is the P19100-004G1 and got it in early 2017 for about $325Can to my door which is about $350Aus. Not sure what the prices are now and they may have a better unit. Bob has played with them and others and would be able to answer to any better models being available. Doing it again I would buy straight from Powtran. POWTRAN Technology

If you are getting into the 5hp range you'll want a 15" fan. Bill's site has the info for making the impeller housing to fit. Once you get to that level you might want to consider a ready made system from CV unless you have found lower cost parts to work with.

The Pentz cyclone is among the most efficient around with the separator lids being the worst. The Thien falls somewhere between.

Just in case you haven't read Bill Pentz's site. Dust Collection Research - Home It is long and repetitive (to get the info to those that skim or cherry pick parts of it) but well worth reading.

If you aren't doing enough woodwork to justify going big, opening up what you have and adding ventilation in the form of a fan or two in the wall/roof to remove the invisible dust will benefit you. Just wear a mask when making dust and for a time after until the ventilation clears the shop.

Pete