Thread: Am I on the right track?

Given the size of the shed and grunt of the CV it doesnt matter that much which arrangement you use.

I would use Option 1 just because of the shorter runs - but put at least one spare Y pointing the other way around about the middle of left hand trunk - same on teh other trunk.

To help declutter things the Small belt and disc sander and the bobbing sander can probably share one 6" arm from the main trunk - add a Y and a couple of best gates to direct air flow.

Rather than use an "always open port"near the cyclone, put blast gates at the end of the trunks and leave them open as needed to act as open ports as this also helps keep the the trunks clear.
Then
If you happen to have two workers in your shed using machines at the same time you might want to be able to close one or both of the always open ports.

At my mens shed we installed a gravity assisted flap gate at the end of the trunk - like this.
This opens when all the other gates are closed, partially open when only 1-2 gates are open and virtually closes when more gates are open.
IMG_1947p.jpg

I didn't bother with this at the Country Shed we did an install in on the week end - the two massive doors along one wall of the shed will provide plenty of ventilation.

Thanks Bob, that’s very helpful.

I like the design of the gravity flap gate!

I'm with BobL in preferring Option 1 for it's shorter trunk lines. In our CVMAX installation, we're making the entire main trunk an 8" diameter trunk line (200mm in your case), then running 6" (150mm) drops off of that main trunk line. In Option 1, this 8" trunk would be your diagonal duct line. (I see this is what BobL has installed in his Men's Shed.)

Using 8" (200mm) for the main trunk line will allow any two machines with a separate connection to the main trunk to be operated at the same time (e.g., bandsaw and table saw). In our case, we expect to have more than one person using the shop at a time. This may not be an issue for you. If it's not, then stay with all 150mm lines for the cost savings as I did in my home shop a few years ago. I do wonder whether the 6" lines can maintain airflow with a second blast gate opened at the end of the trunk line as BobL recommends. Still, easy enough to just close off if not.

Good luck with the project!

Originally Posted by Rushton

I'm with BobL in preferring Option 1 for it's shorter trunk lines. In our CVMAX installation, we're making the entire main trunk an 8" diameter trunk line (200mm in your case), then running 6" (150mm) drops off of that main trunk line. In Option 1, this 8" trunk would be your diagonal duct line. (I see this is what BobL has installed in his Men's Shed.)

Using 8" (200mm) for the main trunk line will allow any two machines with a separate connection to the main trunk to be operated at the same time (e.g., bandsaw and table saw). In our case, we expect to have more than one person using the shop at a time. This may not be an issue for you. If it's not, then stay with all 150mm lines for the cost savings as I did in my home shop a few years ago. I do wonder whether the 6" lines can maintain airflow with a second blast gate opened at the end of the trunk line as BobL recommends. Still, easy enough to just close off if not.

Good luck with the project!

Thanks, a 200mm trunk would certainly be optimal, the price of the 225mm-to-150mm Y-junctions is a bit of a sticking point at the moment - it’ll be around an extra $600 to go in that direction. Maybe I can shave costs elsewhere to make it happen. Possibly if I rely on running the DC as an air scrubber I can do away with some of the room ventilation fans I’m planning to install as part of this project and save some money that way.

I understand the big cost difference! Painful. But, looking at the number of 8x8x6 wyes you'd need, think about taking multiple machines that are not likely to be used simultaneously to a single 150mm branch off of your 225mm trunk. For example, place the buffing/polishing station, drum sander, and 150mm belt sander as separate drops off of a single 150mm branch line beginning from the wye you show from the diagonal trunk at the buffing/polishing station. Same with the thicknesser and jointer on their own 150mm branch with separate drops to each from that branch. That eliminates three of the very expensive 8x8x6 wyes, but you still need the 6x6x6 wyes so the cost savings my not be as great as I'm thinking.

If you're the only one ever using your workshop then 6" ducting is in practice all you will need. Even a CV max can still only pull a max of about 1250 CFM at 50Hz through a single 6" ducting and this is usually reduced to <1000 CFM by machinery constrictions etc. So 9" ducting really only becomes necessary if more than one person is using machinery OR if you decide to go with a "port always open" approach.

You could still use mostly 6" ducting and still have a viable "one port always open' using a small amount of 9" ducting and junctions and set up the "always open" port at the start of the ducting close to the cyclone.

You could slo use LL 6" ducting and just add an exhaust fan for ventilation.

Some people think they're wasting the capacity of the CV by doing this but there are still many other benefits to using a CV like the efficient cyclone, and the benefit of having a DC with a 3 Phase motor and a VFD as at 60Hz it produces about 20% more pressure and hence about 20% more flow.

In my own shed I have two 6" trunks and the rest is all 6" although I do use 4" for things like my DP, TS OH guard, 3 x 4" for BS connections etc. I don't like using DCs for general shed venting as they're too noisy and I really dislike the hissing sound of air going through an open port, and remember if it's not hissing its not moving air.

For general shed ventilation I was fortunate to score two free, quiet squirrel cage fans from the work skip - one moves a real up to 1200 CFM and the other ~1600CFM. The bigger fan vents the welding/spray booth in my Metal work section of the shed, the other is under the highest part of the ceiling above the TS. I can use either of these fans at any time, not just for fine dust removal but also for general ventilation (eg when using solvents or finishes etc) and being just a few hundred watts are a ~1/10 of the cost to run compared to the DC.

If you use the CV MAX with only 6" ducting it will also use less current and therefore use less power so you will have spare power left over to easily run exhaust fans.

I don't usually have more than "me" working machines in my shed but when I have had one other person working there, my particle counters have not noticed any significantly greater dust levels than when I am the only one working. What happens in practice when two people are working machinery they're not always necessarily making dust at exactly the same time. There is also a continuous ~1200 CFM (at 50Hz) of air being removed from the shed. Turning on the ventilation fans and I have significantly more fine dust ventilation than a CV alone.

There might be a little more chip scatter on the floor but as I always end up with some chip scatter, I eventually have vacuum or sweep up anyway.

This all works very well in smaller sheds and to lesser extent in larger sheds.

At the mens shed, as many as 5 or more machines may be running at the same time. At 60Hz the CV Max delivers about 2000 CFM so that means each machine is only getting about 400 CFM of suck which would not seem enough to clear the fine dust, and while there is a slight rise in shed fine dust levels (and more chip scatter) it's nowhere near dangerous levels. What we then do is turn on the Evap AC fan and that clears the fine dust out of the shed. To give each machine 100CFM would require about 3 CV Maxs which is not necessary.

Reading this, if I had a DE connected to one machine, with a flow of 400cfm, plus shed forced venting, that would be acceptable. Interesting.

Originally Posted by Rushton

I understand the big cost difference! Painful. But, looking at the number of 8x8x6 wyes you'd need, think about taking multiple machines that are not likely to be used simultaneously to a single 150mm branch off of your 225mm trunk. For example, place the buffing/polishing station, drum sander, and 150mm belt sander as separate drops off of a single 150mm branch line beginning from the wye you show from the diagonal trunk at the buffing/polishing station. Same with the thicknesser and jointer on their own 150mm branch with separate drops to each from that branch. That eliminates three of the very expensive 8x8x6 wyes, but you still need the 6x6x6 wyes so the cost savings my not be as great as I'm thinking.

Good idea. That would give me a layout something like the following:

workshopplan-ductv4.jpg

I've added the 2x 12" ventilation fans I'm planning to install to this plan as well.

Originally Posted by BobL

If you're the only one ever using your workshop then 6" ducting is in practice all you will need. Even a CV max can still only pull a max of about 1250 CFM at 50Hz through a single 6" ducting and this is usually reduced to <1000 CFM by machinery constrictions etc. So 9" ducting really only becomes necessary if more than one person is using machinery OR if you decide to go with a "port always open" approach.

You could still use mostly 6" ducting and still have a viable "one port always open' using a small amount of 9" ducting and junctions and set up the "always open" port at the start of the ducting close to the cyclone.

You could slo use LL 6" ducting and just add an exhaust fan for ventilation.

Some people think they're wasting the capacity of the CV by doing this but there are still many other benefits to using a CV like the efficient cyclone, and the benefit of having a DC with a 3 Phase motor and a VFD as at 60Hz it produces about 20% more pressure and hence about 20% more flow.

In my own shed I have two 6" trunks and the rest is all 6" although I do use 4" for things like my DP, TS OH guard, 3 x 4" for BS connections etc. I don't like using DCs for general shed venting as they're too noisy and I really dislike the hissing sound of air going through an open port, and remember if it's not hissing its not moving air.

For general shed ventilation I was fortunate to score two free, quiet squirrel cage fans from the work skip - one moves a real up to 1200 CFM and the other ~1600CFM. The bigger fan vents the welding/spray booth in my Metal work section of the shed, the other is under the highest part of the ceiling above the TS. I can use either of these fans at any time, not just for fine dust removal but also for general ventilation (eg when using solvents or finishes etc) and being just a few hundred watts are a ~1/10 of the cost to run compared to the DC.

If you use the CV MAX with only 6" ducting it will also use less current and therefore use less power so you will have spare power left over to easily run exhaust fans.

I don't usually have more than "me" working machines in my shed but when I have had one other person working there, my particle counters have not noticed any significantly greater dust levels than when I am the only one working. What happens in practice when two people are working machinery they're not always necessarily making dust at exactly the same time. There is also a continuous ~1200 CFM (at 50Hz) of air being removed from the shed. Turning on the ventilation fans and I have significantly more fine dust ventilation than a CV alone.

There might be a little more chip scatter on the floor but as I always end up with some chip scatter, I eventually have vacuum or sweep up anyway.

This all works very well in smaller sheds and to lesser extent in larger sheds.

At the mens shed, as many as 5 or more machines may be running at the same time. At 60Hz the CV Max delivers about 2000 CFM so that means each machine is only getting about 400 CFM of suck which would not seem enough to clear the fine dust, and while there is a slight rise in shed fine dust levels (and more chip scatter) it's nowhere near dangerous levels. What we then do is turn on the Evap AC fan and that clears the fine dust out of the shed. To give each machine 100CFM would require about 3 CV Maxs which is not necessary.

It's likely that the CV Max really is overkill; I suppose I am mainly trying to future-proof things in the event that my part-time business grows to the point where I extended the shed or employed a helper. This is going to be time consuming project and I don't relish the thought of buying and installing a CV-1800 only to need to sell it and do it all over again with a CV Max in a few years. And since the CV Max is only 10% more expensive than the 1800 (exclusive of ducts...) it seems a no-brainer.

I agree that ventilation fans are preferable to leaving the DC running all day; the hydroponics fans discussed earlier can be had relatively cheaply so they will be going in no matter what.

Originally Posted by JimmyD

Good idea. That would give me a layout something like the following:

workshopplan-ductv4.jpg

Yes, this is exactly what I was thinking about.

Here's a question I'm having trouble answering from my reading - in the proposed layout below, let's say I'm using the 150mm belt sander at the end of Branch A. So the blast gate at the belt sander is open, as well as the gate the connects Branch A to the trunk.

workshopplan-ductv4.jpg

However, I was using a tool on Branch B earlier, and I have forgotten to close off Branch B from the main trunk. In this hypothetical, all of Branch B's individual tool gates are shut, but the branch itself is still open to the trunk.

What effect does this have on collection at the 150mm belt sander? What if I forgot to close off Branch C too?

What I'm trying to determine is what I can 'get away with' in terms of accidentally leaving branches open. One thing I know about myself is I'm forgetful, especially when busy working.

I know that when the system is actually installed I'm very likely to forget to switch off branches now and again. If this will be a serious detriment to collection then I will be better off 'idiot-proofing' my system by going with just one long trunk with a drop per machine, as opposed to the multiple-branch model.

But my hope is that I can take advantage of the grunt of the CV Max to still get good collection even when I don't close off the right ports.

Thanks to everyone for helping as I try to wrap my head around all of this! The end is in sight.

I understand that BobL is a strong proponent of using a blast gate at the wye off of the main trunk, and I recommend you follow his advice if it makes sense for you. However in my region of the U.S., this is rarely done in smaller shops, including small multi-user shops like the community shop I'm working on now. The recommendation from one of our regional dust collection advisors in the NC Woodworker Forum is to place the blast gate as close to the machine as possible and not worry about a blast gate near the wye. The reason given is that with the gate closed, there is no air flow, thus no turbulence and no static pressure issue. This is what we will do.

Originally Posted by Rushton

The reason given is that with the gate closed, there is no air flow, thus no turbulence and no static pressure issue.

Hi Rushton. The main problem with that logic is that it assumes that the blastgate and pipework is without any leaks - which would be very rare at best.

Pintek - I completely agree with you. You need to be confident your ducts and joints are tight and leak-free. Since I can control the installation, I'm willing to bet on achieving a high degree of tight leak-free fit.

I think you are over worrying a bit.

If you forget to close the blast gate (BG) on one machine (A) while using another, slightly more dust will escape from A at source but some of the escaped dust will be grabbed by the other open gate, and also by the always open gate (AOG).

Let's say you are running the CV Max at 60Hz, so 2000+CFM.

With the port on one machine open, theoretically you should get 1000 CFM through the machine and 1000 CFM through the AOP but in practice machines are more constrictive so you will get maybe 850-900 CFM through the machine and 1100-1150 CFM through the AOG.

If you have a second machine BG open then the split will be something like 600, 600 for the two machines, and 800 for the AOG.

Depending on what your are doing, even 600 CFM will capture virtually all of the fine dust produced at source for many WW situations. More chips will escape but some chips will usually escape anyway. In practice most of the fine dust that does escape will be extracted by the other open gates.

With such a powerful machine as the CV Max, if you wanted to be truly anal about fine dust collection the AOG would be replaced by open BGs on 1-2 machine(s) closest to the one you are using.

Remember if you are using a machine (A) at one end of the shed and the AOG is located at the other there will be two low pressure points in the shed. If fine dust escapes the machine pressure gradient it will enter the AOG pressure gradient and be drawn across the shed to the AOG. It won't all get there as some will drop out of suspension along teh way. This is why if you are going to have a gate open on another machine it's better to use the gate on a machine that is as close as possible to the machine your are using.

If you don't want to shell out for auto blast gates, a budget level solution are $3 pressure switches but some electrical know how is required.
see Making sure your DC is on
I installed these on a few machines at the mens shed and the supervisor reckons its made big difference.
At hime have these on my TS, WW lathe and Belt sander and they work a treat - machine will simply not start unless the machines BG is open and DC is running.