Update: I found this PDF document -on page 13 EBB filters (like P181099) are rated up to 1650CFM while P181038 is an SRG filter which is rated way above 2050CFM ...

Here is their chart; if you search the above doc for the two models you will find the type of filter for each (EBB and SRG)
So practically then both cover the CFM requirements but it all comes down to how heavy is the Dust environment (left side scale)

I'm confused; how do your lungs compare with a truck engine? Is the truck going to die of silicosis 40 years from now because you used an off-the-shelf truck air intake filter, or does it even care, since it burned everything that made it through the filter?

Do you want to bet your lungs and life on a truck intake filter?

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You sound like a fortune teller not like an engineer
0.5 microns is MUCH better that 5 microns.
Microns are microns either for a truck engine or for human lungs
If the Dust Collector was approved to be sold on the american market with a 5 micron bag without being considered a threat to the user then a 0.5micron filter can't be more dangerous, don't you think ?

Please put on your engineer hat, set the fearmongering aside and let's have a technical conversation please

It's not fearmongering; Home Depot sells a crap ton of HEPA filters which have 99.97% effectiveness at filtering even smaller particulates and these are specifically intended for human breathable air.

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I doubt the Harbor Freight dust collector will pull its rated cfm through the 0.5 micron filter. Its most likely rated some other way than drawing through some filter medium. Anyway, 0.5 micron filter would be less porous than the 5 micron filter. 1/10 ?

Ted

The dust collector information doesn't include the differential pressure at your 1550 CFM and neither do the filters.

So there is no way to answer your question without this data.

In general a higher efficiency and lower micron size will need more differential pressure per square metre of filter per m3 sec of air.

You normally find two pressures- clean and dirty. Make sure to allow for monitoring the pressure or flow and changing them when dirty.

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You guys have very good points
Here is some data, measurements done with a 0.5microns filter, the equivanlent of P181038
Source of the data and how it was measured and calculated/aproximated: https://www.youtube.com/watch?v=CjKLIa9vyi4&ab...


So based on your comments it seems that the smaller filter MIGHT cover the needs of this dust collector
It will improve the filtration but it will decrease the CFM. I guess a larger filter translates to higher CFM everything else being equal.

So since both filters will cover the at impeller measured CFM number (which seems to be around 800 either with a bag or with a Whynn filter) the selection of the filter comes down to
how much the smaller filter can limit the CFM.
As per this comment the DC can deliver around 800CFM with the 5micron bag on
The above measurements where taken with the bigger filter at 0.5microns. Since a filter improves the filtration area compared with a bag, but due to a lower micron number increases the resitance to air circulation I could conclude that somehow the bigger filter provides more capacity that the DC would need (since with bag -5microns or large filter 0.5M the measurements seem to be around 800CFM at impeler)

So next it would be to try to guess how much less capacity would the smaller filter provide and try to aproximate the CFM drop

One other thing to think about is whether the filter is designed to flow in to out or out to in....

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Yeah these are designed for a out to in flow while the woodworking requires the opposite.
These have been used by the community for years and I have not heard or red about this to be a problem although they are aware of the difference

In your opinion how could that impact the performance of the filter ?

I'm not a filter man per se, but my understanding is that these filters are actually multi layer components and hence the outer sections trap the larger particles which then gradually reduce down to the 0.5 micron level.

But opposite way, it all immediately clogs up the inner 0.5 micron filter layer meaning your filter needs cleaning much more often or gives you a much higher DP for the same flow.

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Do you have any idea what these yellow marks are ? I am seeing them even on the manufacturer pictures

No idea.

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I believe that the line is to mark which side of the filter is which.
In some designs it may be a glue to hold the filter together during assembly (does both jobs).
As LI said, blowing these the wrong way is not good.
What makes it worse is that the filter rating drops when you do this.
There is more pressure driving the particles against the finest media, and what breaks through can easily escape the coarse side.

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Don't know what to say ..the experience shows that there is lots of woodworkers using these without any visible problems and with a much better performance than the stock bag

Worst case scenario the filter could be installed in a plastic barrel to simulate the housing where it is usually installed

Well a lot of your material is dust / small particles so probably works OK, but would work better if you flow the right way around...

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It would be interesting to know the particle size distribution of the dust that you are dealing with.
My guess is that if we are talking about cutting and milling it is no big deal.
If we are dealing with sanding then it could be a very different matter.

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Yes cutting and milling, not much sanding for me
If the CFM decreases due to reversed airflow I am OK I think the DC is well under what the filter can support even if reversed
If the air filtration performance goes down then that is wasted money ....
Biggest problem right now for me is that the stock bag is practically a fine dust pump.
Everybody confirms that that is the case

The yellow lines are a hot-melt adhesive used to fixture the outer pleats of the filter to the expanded metal mesh, in order to maintain the desired pleat spacing. Otherwise air pressure will collapse the pleats and pinch-off air-flow. Pleats increase the filter surface area per unit of filter volume, but pleats are not self supporting.

Bag filters rely on a build-up of filter cake to increase filter efficiency. Bag filters are not efficient without the cake.

Are we talking about the same bag?
I am talking about this one (the one on top)

Yes, same bags. But saw dust is easy to capture, so a filter cake is less important.

Well if you're all so good at woodwork, why don't you make a filter housing that means the filter works better?

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Well ...I am not that good, not sure where I implied that
However I would consider the idea.
It all comes down to finding an appropriate garbage can or other type of plastic recipient

This would be the setup

Is that still inside to out?

You can just buy a housing for the filter, but they look a bit pricey if you're doing it yourself. Like this https://www.donaldson.com/en-us/engine/filters/pro...

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I would still have the system blowing air through the filter not "sucking it" through

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I read that as out-to-in, the fan is sucking air through the system.
The drum is for settling of coarse materials (hopefully with some baffles inside of it).

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Ed - it will probably work that way as well. It's the way most vacuum cleaners work.

I can't imagine a fan like that will generate much in the way of differential pressure so won't really make any difference.

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@LittleInch

I would still have the system blowing air through the filter not "sucking it" through]

This is what the truck does, right ? It sucks air through the filter
Of course I could imagine a way to blow air through the filter as well

If you ask me the current setup of the Harbor Freight DC is not the smartest one as it sucks dust and debris through the impeller and from there is is pushing it out to the bag filter and that proto separator they have
So practically the impeller could be hit by a piece of wood if it gets sucked in the system -I did hear some impact sounds in a couple of occasions when some debris was sucked in
The above setup will protect the impeler in that sense AND the whole thing is more compact this way

And here is what ChatGPT is saying about it

Is it better for a dust collector to suck air through the filter or to push air through the filter
ChatGPT
For a dust collector, it is generally better to have the air flow in a configuration where it sucks air through the filter rather than pushing air through the filter. This configuration is commonly referred to as a "negative pressure" or "pull-through" system.

Here are a few reasons why sucking air through the filter is typically preferred:

1. Filtration Efficiency: Pulling air through the filter allows the filter media to effectively capture and trap dust particles, contaminants, and debris. The suction created by the dust collector helps ensure that the air passes through the filter media, maximizing filtration efficiency.
2. Dust Containment: With a pull-through system, the filter acts as a barrier between the dust collection area and the exhaust or ambient environment. The negative pressure inside the dust collector helps contain the captured dust within the collector, reducing the risk of it escaping back into the working area or polluting the surrounding environment.
3. Longer Filter Life: Pulling air through the filter tends to put less strain on the filter media compared to pushing air through it. This configuration can result in a longer filter life and reduced maintenance frequency, as the dust and debris accumulate on the outer surface of the filter, away from the clean side.
4. Reduced Pressure Drop: In a pull-through system, the pressure drop across the filter is typically lower compared to a push-through system. This means the dust collector's fan doesn't need to work as hard, leading to potentially lower energy consumption and quieter operation.
5. While a pull-through configuration is generally recommended, it's essential to follow the manufacturer's instructions and guidelines specific to your dust collector model. They can provide insights on the ideal airflow direction and any considerations unique to your equipment.

Hmmm,

Item 1 is rubbish
Item 2 has some legs. A negative pressure system will suck clean air in through any holes or gaps.
Item 3 is rubbish
Item 4 is rubbish
Item 5 is waffle.

A pull through system is much better for the fan but there is a higher negative pressure so collapse is a potential issue.

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If you angle your inlet into that lower bin you'll create a bit of a cyclone filter....

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Seems to me that ChatGPT is hallucinating again. The main reason I see for pull through is to NOT GET ALL THAT DUST IN YOUR PUMP. You can, if you want, but it'll increase the amount of maintenance and repair on your pump.

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The advantage I see with a pullthrough setup is that if the blue container (filter housing) loses pressure it will suck clean air in at most
IF the system is a push through then dusty air will get out of the container through whatever weak points the filter housing has

Buying an off the shelf housing is not something that I want as I that type of housing is too tight and I want to be able to see inside
Ideally I should find a large transparent storage box that can cover the filter entirely and secure that against the top panner using a gasket

Also you might be able to blow the exhaust out of the work shop.... And not cover everything with fine dust.

But yes that's probably a good idea to pull air in rather than let it blow dust out

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Be aware that fire and dust explosions can occur in dust collectors, Any hard shell containment can become a source of shrapnel as well as being another surface to clean. If you really want to direct the collector exhaust outside, place the collector outside, or place a larger plastic bag over the filter bag and duct that outside.

MOst of the workshops for hobbysts like me are set in a garage
Exhausting air outside will create negative pressure in a garage that does not have a lots of openings to get new fresh air in and it will create heating problems over the winter

Fair enough.

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As far as I know, garages are supposed to be ventilated so car exhaust will not collect. Or is that only for attached garages?

Fine dust will still be exhausted into the garage, whether push or pull without outside exhaust.

Ted

Many garages around here were built back duri the 60s and they do not fit the today shops. No ventilation was required back then

There is lots of first hand eperiences shared on line about this setup and it seems that even with an inverted floe these work great no dust

The "pull through" configuration also means the fan is operating on the "clean air" side. This will reduce the need to clean the impeller.

Maybe make a water bath filter.
https://www.youtube.com/watch?v=HaScmB3zY1A