Thread: Difference between these two dust units

Thgey are the same generic 2HP unit, with the restricted impeller throat.
This is another one W394 | DC-3 Dust Collector | machineryhouse.com.au

If you want to improve their performance have a look here

Thanks Bobl. Are these any good?

Really only going to need it for my saw. But I guess it is a snow ball effect and I will use it on other to tools

Sent from my GT-N7105 using Tapatalk 4 Beta

Originally Posted by grantoboy

Thanks Bobl. Are these any good?

Good for what ?

Unfortunately there is no simple answer to your question so let me break it down

Firstly in stock form (ie straight out of the box)
1) Even though they claim to be 1200 cfm they only draw 567 CFM through one 4" inlets (or 608 CFM through two of the 4" inlest) so they do not meet the minimum specification of 1000 cfm needed to capture fine dust at source.
2) Even if they could grab all the fine dust at source, when they are first started up the filter leaks very badly and they need to be run continuously with dust in them for at least 6 hours so the filters clog up enough to start working properly. if you use the DC inside the shed the filter bag should never be washed but just shaken out otherwise the filters leak again
3) 2) would not be an issue if teh DC could be located outside the shed but unfortunately they are not powerful enough to located outside a shed and be ducted to machines inside a shed.

The other reason you want to put the DC outside the shed is because of inevitable leaks in the pressurised side of the system.

If you read the Generic 2HP DC thread you will see that the effort that is needed to get these DCs up to an acceptable level of performance.
NB that modifying the DC is only one half of the battle - 6" ducting is essential and the machines you hook up to MUST use 6" inlets or 3 x 4" inlets connecting to a 6" duct running to the DC.

Originally Posted by grantoboy

Are these any good?

Really only going to need it for my saw. But I guess it is a snow ball effect and I will use it on other to tools

Grant, it is a compromise like almost everything else in the amateur's shed. I have a similar one and it as big as I can run with the power available in my shed. If I ran a 3hp machine I could not run any of the other tools at the same time so what would be the point.

I would recommend doing the mod that Bob posted the link to. If you "bore it out" to 6" and run 6" ducting over a short distance, it will do ok for a tablesaw, provided the collection ports on the tablesaw are modified to 6", or alternately branch it out to run a 6" to the cabinet and a 4" to the overhead guard. Or even if you dont want to modify the port on the tablesaw, 4" to the cabinet' 4" to the overhead guard and 4" just hanging over the table collecting whatever invisible dust it can.

Any of the above combinations would be better than running the dusty unmodded, and just using one or two 4" pipes.

I do not use the collection bags and filters. I run it through a cyclone to separate out what it can and it vents straight outside the shed. With a 2hp machine you will never be able to capture all the invisible dust, so try to have your work area well ventilated as well. The better the airflow through the workshop the more of the invisible dust will be carried out while it is still airbourne. Whatever settles in the shop will be stirred up again by any activity you do in there.

Hope this helps.

Doug

Thanks guys, I plan on getting the carbatec 2hp on and will mod it as mentioned. I also plan on making a cyclone type device (not as flash but same concept) will let you know how it goes once I have my setup going.

Originally Posted by grantoboy

Thanks guys, I plan on getting the carbatec 2hp on and will mod it as mentioned. I also plan on making a cyclone type device (not as flash but same concept) will let you know how it goes once I have my setup going.

I don't want to get into an argument with Doug again over this but unless you use a Bill Pentz (BP) design, any other cyclone design will seriously compromise the flow on such a small DC.

The most vacuum pressure these 2HP can generate is 8.5" of Water Column (WC).
Home made cyclones or any chip catcher will eat up 4.5" of WC, so you will only have about 4" of WC left to play with.
This means a theoretical max of 260 cfm through a 4" duct and 700 cfm through a 6" pipe .
If you modify a 2HP DC according to my generic 2HP DC thread, a needle felt filtered unit will generate 840 CFM and Pleated filter unit will draw 924 CFM, (both with a 6" duct) and if you keep these filters clean you should be able to keep that flow advantage over a home made cyclone and chip collector.

A BP designed cyclone requires 2.25" of WC which leaves 6.25" of WC to play with.
This means a theoretical max air flow of 332 CFM for a 4" duct and 1000 CFM for a 6" duct.
However, I don't think a BP designed cyclone will filter the fine dust out anywhere near as well as a using their recommended 4HP motor and large impeller. This means the cyclone outlet will be dirtier than BP 4HP cyclones. If you are going to use a BP cyclone design on a 2HP DC and locate located it inside a shed you will need to add filters so you will end up back where you started from.

All these flows are of course without adding any ducting, junctions, flexy or throttled machines which will detract from the flows discussed above.

Bob

Not trying to hijack this thread, but given the constraints that you outline for the 2hp generic dusty, what are the alternatives? You can do the mod to the generic dusty as you have described elsewhere, but if someone is starting fresh, are they best off looking at a 3hp dusty to begin with or even a clearvue?

Trav

I would like to know this question also

Sent from my GT-N7105 using Tapatalk 4 Beta

Originally Posted by Trav

Bob

Not trying to hijack this thread, but given the constraints that you outline for the 2hp generic dusty, what are the alternatives? You can do the mod to the generic dusty as you have described elsewhere, but if someone is starting fresh, are they best off looking at a 3hp dusty to begin with or even a clearvue?

Trav

I agree, it's not easy for someone who just wants to dabble in a bit of wood work and buy a couple of second hand machines to then turn around and have to invest a couple of thousand $ in DC gear.

In most cases weekend warriors will progress through a cheap VC, a 1HP DC to maybe a 2HP DC etc and they will be in part protected by the fact that while their working dust levels maybe high the total time they spend exposed is short so their overall exposure will be low. The wood workers that really need to watch out are those that work many hours a week bathed in wood dust. Neither are of course a guarantee of avoiding or striking a health problem. Wood dust health problems like allergies may be triggered at different levels for different people and this is why the minimum specification for successful fine dust removal at source across a wide range of machines, materials and conditions is set high at 1000 cfm (and an air speed of 4000 FPM).

The smallest commercially available DCs that can draw the 1000 CFM over the typical range of conditions found in a medium size home workshop is a 3HP DC with 6" ducting and machine ports modified to take advantage of this.
The problems with a 3HP DC are
- you must keep the bags/filters clean
- you will be limited in the number of junctions and length of ducting, which may not always enable you to locate or vent your DC outside a shed.
If you are prepared to clean bags and keep ducting short then a 3HP and 6" ducting will cope, if not then you will have to go to 4 or more HP such as a Clearvue and maybe even a 8" main and 6" side arms for ducting.

A Bill Pentz style cyclone that vents externally will eliminate the need for filters and bags but the pressure losses generated by BPs cyclone (which is one of the most efficient on the market) is why he recommends using a 4HP motor and associated impeller to ensure the system overcomes these pressure losses and still retains the 1000+ CFM. Adding a any cyclone to a 2 or 3 HP DC is unlikely to achieve the 1000 CFM flow rate required. Remember its 1000 CFM at the machine and not just at the impeller.

Another problem is that not everyones sheds can cope with the electrical loads required by bigger DCs. In that case about the only thing left is a modified 2HP DC - that's why I put some effort into modifying and testing this DC.

Not all machines/operations/materials actually need 1000 cfm, in some cases judiciously applied 800 and maybe even 600 CFM might be enough but short of testing every specific situation we have no way of knowing.

Thanks Bob, that's a helpful summary. Given the comparative costs, I don't think a 3hp is worthwhile - it seems to have many drawbacks of a typical dusty without the upsides of a clearvue. I think it is either a modified 2hp (ideally outside) or a clearvue.

Assuming you dont have the cash for a clearvue, perhaps the most sensible thing would be to start with a 2hp, set it up outside, modified as you and others have shown, with 6" ducting (as straight as possible with few bends or junctions), ending with either 6" ports or 3x4" ports. This is, of course, not always possible, but we can always hope!

Trav

Originally Posted by Trav

Thanks Bob, that's a helpful summary. Given the comparative costs, I don't think a 3hp is worthwhile - it seems to have many drawbacks of a typical dusty without the upsides of a clearvue. I think it is either a modified 2hp (ideally outside) or a clearvue.

Assuming you dont have the cash for a clearvue, perhaps the most sensible thing would be to start with a 2hp, set it up outside, modified as you and others have shown, with 6" ducting (as straight as possible with few bends or junctions), ending with either 6" ports or 3x4" ports. This is, of course, not always possible, but we can always hope!

Trav

I don't see how you can come to that conclusion. Remember, the 2HP starts out already below 1000 CFM. The max flow a modified 2HP can do with clean bags and very short length of ducting is 824 CFM whereas a twin bag 3HP with can pull 1250 cfm.

Then, add ducting and the restrictions imposed by a machine and the 2HP will be even less. At least with the 3HP you have a chance of still getting ~1000 CFM at the machine.

If a 3HP is restricted in the length of its ducting then a 2HP is even more so. If you put a 2HP outside a shed and want to maintain the max flows about the only place you can attach a machine to it is immediately inside a shed. Locating a 2HP inside a shed and venting outside won't work all that well either as the total length of ducting won't change that much.

DC decision economics are somewhat complicated ( i get asked about this all the time) and one needs to look at the total cost and use of any system i.e. DC + Ducting + Power + enclosure + use patterns.

Lets start with the fixed cost
6" ducting and blast gates for a medium size shed are about $500 - this is effectively a fixed cost for all systems that aspire to 1000 CFM.

A 2HP DC is about $300, and while it won't be able to fully utilize 6" ducting it would be silly to use 4" ducting which will further throttle its marginal performance and will need to be replaced if any upgrade takes place.
The minimum install for this system for is $800.

The cost of a decent 3HP system is ~$1000
The minimum install is then $1500 plus the cost of power upgrade if required.

A clearvue costs $2550
The minimum install is then $3050 plus power upgrade if required.

If power installation is not a factor, the base cost approx doubles in every case.
If a power upgrade is required then the cost differential changes accordingly.

The price of an enclosure depends very much on location (inside or outside the shed) and individual entrepreneurship of the shed owner. An external enclosure using all new sound and weather proof materials materials could easily cost $500 to enclose a twin bag 3HP, correspondingly less for a 2HP, and because of its small foot print, less again for a clearvue. Inside a shed will cost less but if shed space is a premium then the clearvue has some definite advantages.

For anyone starting from scratch that wants 1000 CFM at the machine, they will need to use at least the 3HP unit and so will have to upgrade their power. If we allow $1000 for a power upgrade and all new materials on an enclosure, the differential between a 3HP and a Cleavue clearly swings things towards of the Cleavue. Whereas if you already have the power and can source your enclosure materials for next to nothing then the 3HP will still work and you can put the $1500 differential towards something else.

The remaining thing to consider is usage pattern. If a setup involves generation of large amounts of dust (eg involves a lot of timber resizing) then something like a Clearvue makes even more sense. If a setup involves multiple simultaneous use of machinery such as in a men's shed a 3HP won't be able to maintain the flows needed to cope with this. OTOH if you are more of a weekend warrior or occasional user then a 3HP system all still achieve the 1000 cfm but it will mean putting up with the inconvenience of cleaning bags. These days I spend most of my time working metal but when I do want to do a bit of woodwork I'd much rather have a 3HP than a 2HP and simply can't justify a Clearvue type system (yet )

Bobl

Just a quick question and I am unsure if you can answer this. I have no doubt in what you are saying and the figures you are quoting but how is it a company can advertise and sell a product stating it operates at acertain level (2hp machine with 1200cfm) when in fact it is a lot less.

Does this not infringe on our consumer rights ie product being advertised to be able to perform at a certain level but in actually fact can't.

Sent from my GT-N7105 using Tapatalk 4 Beta

Originally Posted by grantoboy

Bobl
Just a quick question and I am unsure if you can answer this. I have no doubt in what you are saying and the figures you are quoting but how is it a company can advertise and sell a product stating it operates at acertain level (2hp machine with 1200cfm) when in fact it is a lot less.
Does this not infringe on our consumer rights ie product being advertised to be able to perform at a certain level but in actually fact can't.

They get away with it because the 1200 CFM is "as measured by THEIR standard test"
The test is in most cases for the impeller only (No bags or constricted inlets/outlets etc)
Some of the test use a single point air speed measurement in the middle of the air stream that does not take into account the friction from ducting walls.
Others use the static pressure as an indicator of flow.
The Impeller of a 2HP Generic DC can generate a static pressure of ~8.5" of WC.
This equates to a maximum flow of 1191 CFM in a short smooth 6" duct, but don't forget that is a theoretical value.
In practice the real flow is more like 1100 cfm.

Even though this is a good pressure and high flow this 12" impeller cannot continue to deliver the oomph needed to overcome necessary restrictions to make it functional.
Adding a Pleated Filer will drop the 1100 cfm flow to 924 CFM, adding a needlefelt bag drops it to 840 cfm.
In contrast a 3HP can deliver 1250 CFM with the bags attached. 1250 V 840 is almost a 50% difference.
Then as the filters and bags clog the 2HP will fall relatively faster than the bigger units - when my bags are half full the flow rate is still ~1000 CFM ie lose 20% flow. When the bags on a 2HP DC are half full the %flow rate loss will be greater. A Clearvue with a bigger motor/impeller will have effectively zero losses as it can get away without using filters.

Now back to the infringement on consumer rights, it's no different to specifications claimed on a heap of products eg
- audio power, outrageous Wattage claims are made but if you read the fine print it will be for a non-standard power representation.
- 0 - 100 km/hr times for motor bikes, ie need a factory tuneup and a 20 kg midget rider
- HP ratings on electric motors, the Chinese manufacturers will print anything you ask for on a label.
- fuel consumption on vehicles - ie granny driver needed

The one that REALLY irrits are the 85dB ear muffs. The impression one gets is the ear muff absorb 85dB of sound.
This is physically impossible because the skull will contact sound around the muff so it is not possible for ANY muff to absorb or cancel more than about 36 dB.
Read the fine print and you will see the claim is that the muffs will reduce a sound with a pressure of say 105 dB down to 85dB so they are in fact only 20 dB muffs.

To a small extent I can understand why the manufacturers do the DC test the way they do and that is because the CFM of the impeller is 9 out of 10 times not the rate limiting step. It's all the "stuff" that is attached afterwards like bags, 4" hoses and ducting, 90º junctions and machines with 4" ports etc.

It does not matter what the flow rate of a 2HP DC is if 4" ducting is used - the 4" ducting is the limiting step at ~400 cfm.

Originally Posted by grantoboy

Bobl

Just a quick question and I am unsure if you can answer this. I have no doubt in what you are saying and the figures you are quoting but how is it a company can advertise and sell a product stating it operates at acertain level (2hp machine with 1200cfm) when in fact it is a lot less.

Does this not infringe on our consumer rights ie product being advertised to be able to perform at a certain level but in actually fact can't.

The quoted figures often irritate me to ... but look at it from the manufacturer's perspective for a moment.

The manufacturer has no idea where and how the unit will be used. Some of the variables are: machine port design and size; length and diameter of duct; number and radius of fittings; amount of flexy. All of these things can severely impact on air flow. The only thing the maker can be sure of is what a naked unit will do. Of course, in the absence of such a standard, the makers will try to make their units look good on paper ... and they do.

It would be nice if there was a more meaningful standard method of rating. For instance, the 2 HP units could all be measured with (say) 5M of 6" PVC inlet duct and 2 M of flexy and the bags fitted, but it is not so.