How much DC is enough?

[keith.d.mullins]

Put in a new shop.  24x16, Not huge but bigger than anything I have had in the past.  Want to move up from my shop vac and dust deputy to a 2HP Grizzly G0548ZP.  The research I see says I should go with 6" pipe, but I am wondering how much it would hurt to go with 4".  I will be running only 1 machine at a time and only do hobby work, weekends, etc.  Have 13" planer, TS, MS, and jointer.  I may add a machine or two, but nothing elaborate, so how much is enough for a hobby shop?

[Just Bob]

My shop is 30x17, and I run 5" throughout to a dust deputy and a HF dust collector.  While I wish I had bigger and better, to be honest, what I have handles everything nicely.  Standard advice is to go as big as  you can afford, or something like that.

[wtnhighlander]

Its only 'enough' if the shop implodes when you start the DC with all the windows and doors shut.

Like clamps, there is never truly 'enough', just a point where it will do.

[Gixxerjoe04]

[keith.d.mullins]

7 minutes ago, Gixxerjoe04 said:

I have spent 1000s of hours crawling through systems like this.  Some for sawdust, some for boiler ash.

If I go 4" PVC I restrict by pipe size.  If I go 6" HVAC pipe I have to use a Tee instead of a wye.  Which restricts the most?  Do either really matter?  Help from you experts please !!

[midtnwoodworker]

I would go with 5" pipe with that collector. I know 6" is the standard, but with a small collector like that grizzly I think you will be better off with 5" and running one machine at a time. Either way you go you should be fine as long as you keep all the blast gates closed except for the machine you are using. This is only talking about chip collection mainly because you would need a much larger collector to capture all the fine dust.

[Eric.]

I have that DC with 4" pipe and the system is inadequate if you're interested in your health. It collects the big stuff okay but not the fines. It's not the size of pipe that's the weak link either, it's the whole system. If you want truly efficient DC you need a 5hp unit minimum with 6" pipe. 2hp units are chip collectors, not dust collectors.

[RichardA]

25 minutes ago, Gixxerjoe04 said:

Get away from my house!!!!!!

[keith.d.mullins]

I understand the difference between collecting chips and fines.  I'm not interested in spending the $$ for fine particle collection.  I will put in some type of filter to assist with them,  but my exposure won't be extremely high.  I plan to put a SDD cyclone in place soon, but want to see what the system runs like without it first.

 

What would be the advantage of 5" vs 6"?  Is it just the cost or is their an underlying benefit?

I do want to thanks you all for helping me out here.  I am a DC newbie.

 

[Chestnut]

2 minutes ago, keith.d.mullins said:

I understand the difference between collecting chips and fines.  I'm not interested in spending the $$ for fine particle collection.  I will put in some type of filter to assist with them,  but my exposure won't be extremely high.  I plan to put a SDD cyclone in place soon, but want to see what the system runs like without it first.

 

What would be the advantage of 5" vs 6"?  Is it just the cost or is their an underlying benefit?

I do want to thanks you all for helping me out here.  I am a DC newbie.

 

Well your collector is going to flow so much air and if you increase pipe size the air moves slower and your more likely to get blockage. The difference between 5" and 6" isn't linear. 6" will offer less resistance to higher flows.

 

[Eric.]

I have the SDD as well and I exhaust out of the back of my shop.  If you have a garage shop and you're not that worried about the fines, then that system will be okay for you...it'll clean up most of the mess.  But if you are in the basement and/or you want to pull the dangerous crap out of the air, you need a bigger system.  If it's the former, don't give it much thought...it's just a giant vacuum and most any rigged system will do the job.

[Ronn W]

There is no point in making your dust work any larger than that inlet size since the smallest diameter will govern your airflow.  Isn't that unit equipped with 4" inlets?

I have a similar sized Laguna unit with 4" inlets and used 4" ducts.  Works fine on one machine at a time.  Max "equivalent distance" of straight pipe is about 20".

[TerryMcK]

If you are only using it on one machine at a time and as it is on wheels you could just wheel it close to the machine you are using and connect with a shortish flexihose. Lots of weekend warriors do that and it is more than acceptable for a hobby shop on a budget. It still won't be massively successful collecting fines but will be ok for larger sized particles. This is ok for machines with 4" ports.

I'm guessing your 13" planer doesn't have a 4" port though? As you are reducing from 6" to 4" to (maybe) 2.1/2" then air flow to the extractor will be compromised. In that case it's better (but still not perfect) retaining your shop vac and dust deputy for that machine.

There ain't no substitute for cubic inches (heard that somewhere  ) and the more horsepower you have the more dust and chips will be collected. 

Just make sure you wear PPE during and after any milling processes. Invest in an aircleaner too to keep those invisible suspended fines out of your lungs.

[gee-dub]

I don't understand the comment about having to use a T instead of a WYE if you go with 6" pipe?  I have several 6" WYEs in my system.  I would never use a T; if it were unavoidable, I would find a way to avoid it ;-)

 

[Eric.]

As an aside...

I have a 5" inlet on my DC, which I assume is what OP will have as well.  Ideally you would use 5" pipe for your main if you have a 5" inlet, but 4" sewer and drain PVC is so cheap that it makes it foolish to use anything else.  Like I said before, unless you're putting together a real system with a 5hp or larger system, you're making the decision to settle for sub-par collection, at which point you may as well save some money and put together a "good enough" system with the singular goal of picking up most of the mess.

Just to beat the dead horse once more...if you have a basement shop and/or you want to keep your lungs clean and pink without wearing a respirator 100% of the time, a 2hp unit will not be adequate no matter what kind of pipe you use.  I have a garage shop and wear my respirator when doing procedures that kick up tons of fine dust...I blow out the shop with a backpack blower on a regular basis...so my system serves my needs for the most part.  If I had a basement shop the DC would be much higher on the priority list and I would have a 5hp unit along with air cleaners.

[Guest]

How are you venting? If direct venting you can get away with less power.  If pushing through a filter stack or filter bag you need more power.   Ross is right, you can never have "too much" but I don't think most people realize that direct venting is even an option.   Eric would probably have a lot more fine dust all over the place if he did not direct vent.   

I use a festool extractor for fine dust: sanding, my overblade TS port, router table and near my bandsaw blade.  I save my bigger DC for large chips: bottom port on TS, Jointer and planer.   It is a bit of a workaround until I install a real system, but works for now 

[ben_r_]

You lose a lot by reducing a main inlet from a 6 inch to a 4 inch. You should try and keep your main vain the same size as your inlet and slowly reduce the branches down to the machine size. For example 6" inlet --> 6" main vain --> 5" wye branches --> 5" flex hose or straight pipe --> 5"-4" reducer --> machine port.

[Tom Cancelleri]

I recently did ducting and a dust collector in my shop. I went with a Clearvue 5hp cyclone. While I was half tempted to go with nordfab I couldn't justify $3500 for pipe. I went with 26 gauge snaplock hvac pipe. I'm getting over 1100 CFM and over 5000 LFM velocity at my drops, which is more than enough for collecting fines and chips. If you're going to go with a less than ideal ducting solution, up the power of the machine to compensate for the loses in the ducting. 

[JpPhysics]

So I may be a bit late to this but here is my 2 cents worth.  I think you should approach the problem from an engineering perspective.

Your system posts a max flow rate of 1700 CFM.  That is brand new, out of the box with nothing hooked up, so let's say you can reliably get about 1500 cfm with a moderately dirty filter and some duct work attached.

In order to keep the sawdust, chips and stuff moving you need to maintain a minimum air velocity.  Branch lines should hit 4000 fpm while the main branch may drop down to 3500 fpm.  These seem high but lots of studies have been done by people smarter than I and this is what they tell me.

So 1500 CFM thru 6" Duct is 7639 fpm, that's plenty fast to keep stuff moving as long as your duct runs are short.

This is where the engineering comes in:

• 6" Duct      7639 fpm    14.7 in water loss per 100 ft pipe
• 5" Duct      11000 fpm   36.6 in water loss per 100 ft pipe
• 4" Duct      17000 fpm  112 in water loss per 100 ft pipe

What this effectively means is that the longer your pipe or the more inches of water loss in your system, the less actual CFM you will get.  My guess is that with your system running a purely 4" pipe you will only pull 450 to 550 CFM.  The fan will "Cavitate" for lack of a better term.  You would be better off running bigger duct as the main trunk line then branching off to your equipment. Here is a picture of a typical Fan Curve.  The higher the pressure (Y axis) the less volume of flow we get (X axis).  Every fan is different, and Grizzly should be able to provide you with a fan curve for your system.

Additionally we can estimate the pressure loss in fittings using ASHRAE charts.  Here are some typical values for the size you are interested in.

• 90° Elbow (Long Radius) - 6" = 18 ft of pipe          5" = 15 ft of pipe         4" = 12 ft of pipe
• 90° Elbow (Short Radius)      No Data                          No Data                      13.4 ft of pipe
• 45° Elbow (Works as a WYE)      8ft of Pipe                    6.75 ft of Pipe            5.1 ft of pipe

The problem becomes when you have all ports closed but the one you are using.  If the port is sufficiently small say 2" or 3" you may not pull enough air thru the system to keep the dust moving once you hit the trunk line.  Let's say it does throttle down to about 550 cfm thru your 4" port at the tool.  550 CFM thru a 6" duct is 2801 fpm.  Studies have shown that this will cause your main trunk line to clog up over time.  The solution is to open up another port at the end of the line somewhere to let in more air.

I hope this all makes sense, let me know if you need more information.

Resources:

Spec Sheet for your dust collector

Duct Velocity Calculator

Wood Magazine Article on Dust Collection

Equivalent Friction method for duct sizing

[Eric.]

That's all great, JP, but none of it changes the fact that a 2HP unit will not adequately collect fine dust, no matter the size of pipe used nor how many turns nor the degree of the turns.

Bill Pentz's site has done all of the research for us.  I can't remember the exact numbers and there's no way I'm gonna read it again, but the bottom line is you need WAY more blower power and duct size than you think you do.  And the system has to be engineered correctly to boot.

On the other hand, if you just need to pick up your mess, a 2HP will be just fine, and there's no need to do a lick of math because it doesn't matter.

There's a BIG difference between a dust collector and a chip collector.  They should make it illegal to label any unit smaller than 5HP a dust collector.  They should call it a chip collector, because that's mostly what it collects.

[keith.d.mullins]

12 hours ago, gee-dub said:

I don't understand the comment about having to use a T instead of a WYE if you go with 6" pipe?  I have several 6" WYEs in my system.  I would never use a T; if it were unavoidable, I would find a way to avoid it ;-)

 

I haven't been able to find any HVAC Wye connections.  Maybe I'm not looking in the right place.

2 hours ago, JpPhysics said:

So I may be a bit late to this but here is my 2 cents worth.  I think you should approach the problem from an engineering perspective.

Your system posts a max flow rate of 1700 CFM.  That is brand new, out of the box with nothing hooked up, so let's say you can reliably get about 1500 cfm with a moderately dirty filter and some duct work attached.

In order to keep the sawdust, chips and stuff moving you need to maintain a minimum air velocity.  Branch lines should hit 4000 fpm while the main branch may drop down to 3500 fpm.  These seem high but lots of studies have been done by people smarter than I and this is what they tell me.

So 1500 CFM thru 6" Duct is 7639 fpm, that's plenty fast to keep stuff moving as long as your duct runs are short.

This is where the engineering comes in:

• 6" Duct      7639 fpm    14.7 in water loss per 100 ft pipe
• 5" Duct      11000 fpm   36.6 in water loss per 100 ft pipe
• 4" Duct      17000 fpm  112 in water loss per 100 ft pipe

What this effectively means is that the longer your pipe or the more inches of water loss in your system, the less actual CFM you will get.  My guess is that with your system running a purely 4" pipe you will only pull 450 to 550 CFM.  The fan will "Cavitate" for lack of a better term.  You would be better off running bigger duct as the main trunk line then branching off to your equipment. Here is a picture of a typical Fan Curve.  The higher the pressure (Y axis) the less volume of flow we get (X axis).  Every fan is different, and Grizzly should be able to provide you with a fan curve for your system.

Additionally we can estimate the pressure loss in fittings using ASHRAE charts.  Here are some typical values for the size you are interested in.

• 90° Elbow (Long Radius) - 6" = 18 ft of pipe          5" = 15 ft of pipe         4" = 12 ft of pipe
• 90° Elbow (Short Radius)      No Data                          No Data                      13.4 ft of pipe
• 45° Elbow (Works as a WYE)      8ft of Pipe                    6.75 ft of Pipe            5.1 ft of pipe

The problem becomes when you have all ports closed but the one you are using.  If the port is sufficiently small say 2" or 3" you may not pull enough air thru the system to keep the dust moving once you hit the trunk line.  Let's say it does throttle down to about 550 cfm thru your 4" port at the tool.  550 CFM thru a 6" duct is 2801 fpm.  Studies have shown that this will cause your main trunk line to clog up over time.  The solution is to open up another port at the end of the line somewhere to let in more air.

I hope this all makes sense, let me know if you need more information.

Resources:

Spec Sheet for your dust collector

Duct Velocity Calculator

Wood Magazine Article on Dust Collection

Equivalent Friction method for duct sizing

Great information.  This is very helpful.  Thanks a ton.

I plan to start moving the system from tool to tool.  Once I am somewhat comfortable with the equipment location I plan to run the duct system.  Filter with the original system filter and eventually locate the DC in an addition exterior extension to reduce noise and vent directly to the exterior.

If I add the SDD, how much visible dust and chips would be vented?  Don't want to upset the neighbors.

[Tom Cancelleri]

Chips won't vent out unless your bin is full. Fines won't really be seen as they are expelled in the air. Those fines are the sub 5 micron particles that hang around in the air and eventually settle on your tools.

Sent from my Nexus 6P using Tapatalk

[wtnhighlander]

Plan your 'external' vent so that it comes out behind a shrub. Know one will ever know. Until you overflow the bin.

[JpPhysics]

On 7/20/2016 at 6:26 PM, keith.d.mullins said:

I haven't been able to find any HVAC Wye connections.  Maybe I'm not looking in the right place.

Great information.  This is very helpful.  Thanks a ton.

I plan to start moving the system from tool to tool.  Once I am somewhat comfortable with the equipment location I plan to run the duct system.  Filter with the original system filter and eventually locate the DC in an addition exterior extension to reduce noise and vent directly to the exterior.

If I add the SDD, how much visible dust and chips would be vented?  Don't want to upset the neighbors.

Here in Oregon I go to a place called Vinji and Sons, they provide HVAC equipment and supplies to the home owner.  You could try any HVAC supplier or dealer or even try a Sheet metal shop in your home town.

Here is the Amazon link, but I think you can get it cheaper local.

https://www.amazon.com/Galvanized-Metal-Connecting-Fittings-Ventilation/dp/B00B93MZ3C/ref=sr_1_1?ie=UTF8&qid=1469202800&sr=8-1&keywords=6"+wye

Good luck with your set-up, half the fun is getting everything to work the way you want!

[keith.d.mullins]

Thanks JP