Thread: Dust extractor round two!

Originally Posted by hellofellow

How much better will the 2HP be ( 1200CFM) VS the 1HP (650CFM). Will it actually collect those finer particles even though the hose connects under the table?
The final thing to note is if I do get the 2HP I will need several meters of flexi pipe to even reach the tablesaw in the centre of the shed. There is no way I can have it in very close proximity. Will this affect how well the dusty works? The smaller unit on the other hand I could almost sit under the table and have 0.5m pipe.

I know this is a bit long winded, but I figured it was time to upgrade my dust extraction before buying any more nice tools!
Really appreciate the opinions. I know the 2HP is a better option but really am curious how much difference it makes and if it will be redundant if the flexi pipe has to be too long!

The CFM ratings by the manufacturers are performed according to a standard cannot result in an accurate measurement , and fails to take into consideration the typical conditions encountered in small wood workshops. So throw the 1200 and 650 CFM out the window.
Bill Pentz recommends a system have ~1000 CFM to be able to capture fine dust at source. If it is not captured at source its like letting bugs free in a hospital environment and hope you can catch them later. Good shed ventilation(a flow across the shed between a window and door opposite is an example) helps but on still days you will be working in a fog of fine dust.
The 1000 CFM is a sort of high standard and requires a 15A plug and socket motor to get this. I realise that not every one has this so what I advise people is to get as close as you can.

If you use 4" ducting unless you connect up something approaching a jet engine you will never get more than about 425 CFM through a short length of duct. It acts like a chokepoint and the longer it is the less flow there will be.

The 1HP systems I have measured using say 3m of 100 mm ducting or 2m of 100mm flexy, one the filter bags start to load up (condition) their small fan finds it very hard to shift any are against this and typical flow rates are around the 325 CFM. This is less than one third of the recommended flow.

The standard 2HP systems only get to around 400 CFM if 100 mm ducting or flexies are used. However they can get to ~900 CFM if they are modified to use 150 mm ducting (machines dust ports have to be modified to accept the 150 mm as well) and use a pleased filter.
Look here The Generic 2HP DC

In practice the flow will reduce as the filters load up but it should still be possible to get close to 800 CFM. this is not ideal but WAY better than the 1HP unit and not that much better than some users get with bigger DCs because now the limit is the air flow path through the machine.

A 1HP will only get ~600 CFM with 150 mm ducting but as the small filter conditions this will drop to around 400 CFM or less because the fan is not powerful enough to pull the air against increased resistance and increasingly goes round and round (cavitates) but not move much air. It may also overheat and damage the small motor.

All this is moot because unless you put or vent the DC outside the shed, the shed will eventually fill with fine duct anyway. All DCs (eventually leak) and there's very little that can be done about it.

In short the stock 2HP is only marginally better than the 1HP but the modified 2HP is a lot better than even a modified 1HP machine

Thanks very much BobL.

Some very basic questions seeing I have never had an extractor.

1. So is there any difference in flow between ducting and flexi? This might also seem very basic, but are they literally just two different types of pipe? One is the flexi plastic/pvc hose and ducting is just a different material? Can you put either on the dust extrator...?

2. So , as a rule...the longer the ducting/Flexi the less CFM? Ie if I have 4m of flexi to my tablesaw ill get less CFM than if I had two meters? ( stock with no mods).

3. The wider the flexi/ducting the higher the CFM? i.e. 150mm vs 100/4inch?
I would of thought that less diameter would mean more pressure/ greater vacume not the other way around.

4. If I connect 150mm piping from the dust extractor would this still not only be limited by the size of the port on the side of the machine ( both dust extractor and saw)? thus why port size needs to be modified... would there be any benefit whatsoever to using 150mm pipe without modifying the port?

5. When you say the dust extractors eventually leak unless you duct them out of the shed.. is this a process that takes years as the machines become old, or just as the bag starts to fill there will be leakage all the time? Out of curiosity can you duct these basic machines out of the shed without modifications?

6. Finally, to collect fine dust I have heard in both threads people say (including yourself) you need 1000CFM "at the source".. using a table saw as an example-
Does "the source" count as the vent below the table saw- or do they mean additional dust extraction right above the blade. Ie if you theoretically had a 15amp socket and a 3HP dusty connected to the standard tablesaw vent, this should in theory capture the fine dust..

7. Oh and having a look through other posts there is a "theoretical maximum " you can get through 4 inch flexi.... Does this mean no matter the HP/size of your dusty, you will simply not get greater than 425CFM if using 100mm flexi into a 4inch port?

I know these are basic questions, and I even remember you have a thread on modifying a 2HP dusty which I am about to go and browse so I apologise if all of this is covered elsewhere. Just felt the need to nut out a few quick questions as id have to make the decision which to get tomorrow.

Kind regards,

Andrew

Originally Posted by hellofellow

Thanks very much BobL.

Some very basic questions seeing I have never had an extractor.

1. So is there any difference in flow between ducting and flexi? This might also seem very basic, but are they literally just two different types of pipe? One is the flexi plastic/pvc hose and ducting is just a different material? Can you put either on the dust extrator...?

The issue with flex is that it goes all the way from Ag drainage pipe with large corrugations to smooth wall that approximates smooth wall PVC pipe.
The average flexy sold by Carbatec and others has a reasonably smooth wall and will have a flow rate about 5% less than smooth wall PVC pipe.

2. So , as a rule...the longer the ducting/Flexi the less CFM? Ie if I have 4m of flexi to my tablesaw ill get less CFM than if I had two meters? ( stock with no mods).

Yes it will be less - how much less depends on the initial amount of suck and the size of the duct and the performance of the fan..
the difference between 4m and 2m @ 400 CFM in a 100 mm duct is about a 5% loss of flow, flex will be 10% .

All of these are relatively small amounts but they soon add up, Flow is affected by bends and junctions, filters especially hen they get dirty and machinery duct port and internal air flows as well - they all compound on each other and it does add up very quickly.

3. The wider the flexi/ducting the higher the CFM? i.e. 150mm vs 100/4inch?
I would of thought that less diameter would mean more pressure/ greater vacume not the other way around.

You cannot make pressure by reducing the duct diameter - the pressure is determined by the fan size, design and RPM.
Under the same suck performance of a fan a 100 mm duct can will only carry about 1/3rd of that a 150 mm duct. This is due to the wall resistance of the narrower duct.

4. If I connect 150mm piping from the dust extractor would this still not only be limited by the size of the port on the side of the machine ( both dust extractor and saw)? thus why port size needs to be modified... would there be any benefit whatsoever to using 150mm pipe without modifying the port?

Absolutely - you have to open up the port on your machine. On my TS I had a crappy 75 mm duct at the back of the blade. I threw the hood and port away and rebuilt a hopped into the bottom of the cabinet and added 150 mm port - works like a dream.

I know this upsets people to have to take an angle grinder to a new machine but there not really any other choice.

5. When you say the dust extractors eventually leak unless you duct them out of the shed.. is this a process that takes years as the machines become old, or just as the bag starts to fill there will be leakage all the time? Out of curiosity can you duct these basic machines out of the shed without modifications?

Some leak right out of the box, others take time. The major problem area is the plastic collection bag - as sawdust rattles around inside they develop pin hole and leak like sieves. The other area is the collection/filter bag to housing seal - one ruck in the plastic can fill a shed with fine dust in a few minutes. By the time you see the leak on the side of the bag the shed will be half filled with fine dust.

6. Finally, to collect fine dust I have heard in both threads people say (including yourself) you need 1000CFM "at the source".. using a table saw as an example-
Does "the source" count as the vent below the table saw- or do they mean additional dust extraction right above the blade. Ie if you theoretically had a 15amp socket and a 3HP dusty connected to the standard tablesaw vent, this should in theory capture the fine dust..

On a TS )more is always better but the most common thing to do is to place about 2/3rd of the suck on the cabinet and 1/3 on the overhead guard.
This would require a 150mm duct on the cabinet and at least a 75 mm on the guard but most people use a 100mm on the guard.

7. Oh and having a look through other posts there is a "theoretical maximum " you can get through 4 inch flexi.... Does this mean no matter the HP/size of your dusty, you will simply not get greater than 425CFM if using 100mm flexi into a 4inch port?

The fan has to be able to move that much air to begin with. e.g. You cannot put a 100mm duct on a vacuum cleaner and expect it to move 425 cfm. The fan in the vacuum cleaner only moves about 125 CFM and cannot move any more. A big (5HP motor) and large impeller will move more than 425 but it won;t be much more. The are some fans that can move a lot more than 425 CFM through a 100mm pipe but to do this they develop a much higher suck so that special ducting is needed to cope with the pressure. They scream like crazy and if you were to use regular flexy on these fans the flexy would collapse. This is why DCs work in a specific pressure/flow range as noise becomes a major issue.


It sounds like you need to spend a few days reading the threads in this forum. Also look at the stickies for ideas.
Also if you have a few spare days look at Bill Pent website.

Thanks very much.
Really appreciate your long and thourough answers.
I do need to to more reading I totally agree, it just came up suddenly and the smaller one is two hours away and I happen to be in that city tomorrow so needed to make my mind up tonight. ( I normally read threads for hours before posting)!

I guess I have two final questions for you- 1. Carbatec sells Flexi but not duct? Where would I look at some prices for duct for this purpose?

2..Assuming I'm not going to modify any time in the very near future ( although I will aspire to at some stage) which would you get if you were in my limited space position?

For anyone ever in my position;
My thoughts are as follows:
I figure at either of those prices $200 for a $389 machine in good condition or $100 for the normally $250 more portable machine I should nearly get my money back if I do decide to upgrade again so price is not too much of an issue in this instance.

Guess seeing there is minimal difference in CFM without modification the biggest downside to the smaller unit is storage capacity and big advantage is manoeuvrability. I guess you could also say no plastic collection bag to leak is an advantage as it only has the cotton bag!

Big advantage to the 2HP one is capacity and ability to modify when I have the time. Without modification the 2HP unit has a slight advantage in CFM but not enough to make me jump up and down.

The dilemmas of buying new equipment ay. Wish I could win the lotto

Anwyay thanks again to BobL. I really do appreciate your time in answering my rather basic questions.

Cheers

Originally Posted by hellofellow

I guess I have two final questions for you- 1. Carbatec sells Flexi but not duct? Where would I look at some prices for duct for this purpose?

If you read the forum you will see that nearly everyone uses PVC ducting.
There are two type commonly use
DWV - sewage pipe - its grey in colour
Storm water - its cream in colour and a little thinner than DWV
The sizes and fittings will fit fit either
DVW is more expensive but sometimes suppliers only stock DVW for the lesser used connections
Bunnings have it but if you go to a dedicated Retic or plumbers supplies you will get a MUCH better deal

I supposed you are going to go and buy a bunch of 100mm ducting ? SIGH - if you buy and eventually end up modifying the 2HP you will kick yourself or not installing 150 mm.
Doing the ducting twice has to be a major PITA.

2..Assuming I'm not going to modify any time in the very near future ( although I will aspire to at some stage) which would you get if you were in my limited space position?

The 2HP wins hands down

I figure at either of those prices $200 for a $389 machine in good condition or $100 for the normally $250 more portable machine I should nearly get my money back if I do decide to upgrade again so price is not too much of an issue in this instance.

It's not worth $389 to start with

Guess seeing there is minimal difference in CFM without modification the biggest downside to the smaller unit is storage capacity and big advantage is manoeuvrability. I guess you could also say no plastic collection bag to leak is an advantage as it only has the cotton bag!

You didn't mention cotton bags. Cotton bags are the worst - they simply don't filter any fine dust

Big advantage to the 2HP one is capacity and ability to modify when I have the time. Without modification the 2HP unit has a slight advantage in CFM but not enough to make me jump up and down.

After the 1HP has made a mess of the shed you will regret it. AT least with the 2HP always modify it and solve a few problems.

I would start by buying the 2HP and some flexy.
Then save pennies and buy and install 150 mm ducting and junctions (keep using the 2HP and flexy) - it will take you a lot longer than you think to install the ducting so you don't want the DC out of action while you do this
Then modify the 2HP.

Just FYI . I recently measured the airflow of a 2hp dusty with pleated filter and got 350CFM with 1m of smooth bore 4" flex and around 250 CFM with 4m of carbatec 4" flex. I would be looking at the 2HP as a minimum and taking Bob's advice regarding future mods and 150mm pipe / hose. Is enclosing it outside your shed not an option? Running it inside will only serve to pump the really fine dust around in the air.

Thanks guys! Really appreciate it. BobL thanks again for your patience and replies.
Ill go for the 2HP Dusty.
Interesting about the cotton bags. The 2HP the top half appears to be cotton as well, just the bottom half collector bags are plastic. Where as the mini 1HP dusty just goes straight into the cotton bag ( pictures in the carbatec link). (https://www.carbatec.com.au/dust-con...4kg-44-41-42cm).

Out of pure curiosity are there any 2HP dust extractors on the market that actually utilise their 2HP?- ( If price was not an issue and one did not want to do any modification)..Are any better than the standard hafco and carbatec ones... I see Jet makes a 2HP one for 800$$!!!!
Im sure knowing Jet half of this is purely due to the brand name though any difference in actual stock CFM? Maybe that would be the perfect compromise if if it existed between a modding a 2HP and buying a 3HP dusty if one had the cash ( I don't ). I do note that the stock port is 150mm although it also has a Y splitter on it. I guess thats a good start... ( but not worth an extra 600$)!!!.

Anyway thats enough dust extraction from me. Next time you here from me in this forum it will be time for another upgrade! Probably will have a nice 3phase 15amp shed and it may be time for a 3HP dusty or a cyclone ( One can wish).

I guess I should buy another good shop vac too for the smaller tools! I hear Aldi has a cheap one thats not too bad!

Thanks all

Andrew

[QUOTE=hellofellow;1946978] Interesting about the cotton bags. The 2HP the top half appears to be cotton as well, just the bottom half collector bags are plastic. Where as the mini 1HP dusty just goes straight into the cotton bag ( pictures in the carbatec link). (https://www.carbatec.com.au/dust-con...4kg-44-41-42cm).[/QUOTE]

The filters on the newer 2HP are not cotton but needle felt this is a much better filter than plain woven cotton.
Needle felt is as good as pleated paper filters at flirtation, played filters of course take a lot longer to clog up and can be cleaned better without removal of the filters.

[QUOTE]Out of pure curiosity are there any 2HP dust extractors on the market that actually utilise their 2HP?- ( If price was not an issue and one did not want to do any modification)..Are any better than the standard hafco and carbatec ones... I see Jet makes a 2HP one for 800$$!!!!
Im sure knowing Jet half of this is purely due to the brand name though any difference in actual stock CFM? Maybe that would be the perfect compromise if if it existed between a modding a 2HP and buying a 3HP dusty if one had the cash ( I don't ). I do note that the stock port is 150mm although it also has a Y splitter on it. I guess thats a good start... ( but not worth an extra 600$)!!!.[/QUOTE]
The crucial difference that is not price related is the size of he connection between the impeller and bag.
On most generic 2HP DCs this is a 125mm flexy connection. There are at least 3 that are bigger. One is the Timbercon and the other is the carbatec unit that has the impeller attached direct to the bag housing.
The other is a a unit that uses a 150mm flexy so no modification of that (the most tricky) end is needed.

[QUOTE]I guess I should buy another good shop vac too for the smaller tools! I hear Aldi has a cheap one thats not too bad![/QUOTE]
Don't get me started on Shop Vacs )