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Offlineanontemp
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flow hood - - filter questions
    #20330427 - 07/26/14 02:59 AM (9 years, 8 months ago)

I am looking for 24x36 filters.

I keep coming acrost the 'Flanders Laminar Flow Grade" filters. Are these any good? I am 'guessing' they are parked as Laminar Flow because of the low resistance (0.3)

And then this one, http://www.fungi.com/product-detail/product/36-x-24-x-58-micron-filter.html
I would order but it has no specs! I know its good 2 go because its from fungi but I need filter specs to make my box!

Anyone here use the Flanders hepa filter? or anyone know good 24x36 filters?

I am planning on getting a nice blower as well. 4 Speed 1/3hp. CFM @ 0.90SP  1059/926/826/813

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Offlinetombosley8
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Re: flow hood - - filter questions [Re: anontemp]
    #20330537 - 07/26/14 03:45 AM (9 years, 8 months ago)

here's a good tek i used for my 24x24 flowhood... http://www.shroomery.org/forums/showflat.php/Number/19798444 I think you might need a bigger blower for that but i'm definitely not the best adviser on that one. I have this one but only because i wanted to be able to use it in the future when i got a filter and the space for a filter the size you looking for or bigger. I do have to drastically minimize airflow to recieve laminar flow ( bic lighter two inches away should be bent at a 45 degree angle NOT 90 as swazey says in the tek) . I'm using a speedster as swazey does and I have to block off a good 60% of the intake. Read the first few comments and you'll see. My flowhood is working great so far and i wish the best to you with yours. I kinda wish i had gotten my filter from the brand swazey lists because the filter face style is not the zigzagged metal like mine. It appears that his style filter face is not as easy to damage as mine although any damage i have been able to repair for the most part by bend the metal back. Either way the link he provides is a great company with quality products at an affordable price. I got mine for similar price off ebay.


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Offlineanontemp
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Re: flow hood - - filter questions [Re: tombosley8]
    #20330558 - 07/26/14 04:00 AM (9 years, 8 months ago)

Well I am going to get one of these Flanders Laminar filters. I found a 22 x 46 on ebay for so cheap, http://www.ebay.com/itm/220816146826?item=220816146826

That with a 8" canfan maxfan that can put 600cfm~ @ 0.375 SP should be enough air. I'm just not sure if there needs to be CFM added for the filter/box size. It wouldn't seem like it. If I need more CFM then I can just get 1 of those cage fans same price. Picked the canfan for the noise level

If now one has objections to that filter/fan combo I am going to get'em.

Edited by anontemp (07/26/14 04:04 AM)

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OfflinePussyFart
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Re: flow hood - - filter questions [Re: anontemp]
    #20330650 - 07/26/14 04:58 AM (9 years, 8 months ago)

You want a blower, not a fan.

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Re: flow hood - - filter questions [Re: PussyFart]
    #20330759 - 07/26/14 06:13 AM (9 years, 8 months ago)

that can fan won't do shit with that filter. I believe that laminar flow is created with high amount of resistance on the back of the filter in the plenum to create even flow across the entire face of the filter. The can-fan may be able to push air through the filter (barely any at all)but it will not be laminar flow. for that filter (EDIT: actually for one that size with better stats for laminar flow) you are going to need a decent blower. When it comes to that spectrum of airflow with that kind of resistance your best bet for your money is a blower similar to the one i have linked to0 above. Zoro tools and ebay have pretty good deals on decent blowers. The exact math for how much cfm you need your blower to be to match the filter isn't so crucial if you have a speedster and a overpowered blower. The bic test is really good to find laminar flow. An under preforming blower will lead to plenty of failure. TRUST ME.  I think the blower i have would suit you well with a speedster for that size filter but the filter you linked to i'm afraid you are going to have trouble getting true laminar flow through. You want to find a filter that is tested at a resistance around 1" w.g. and a higher cfm (preferably around 800-1000 ?? with a 2x4 size filter {i think???? hopefully someone chimes in with better or more accurate answer to that)
here is a part from fungifun.com 's  flowhood build tutorial to help you understand better...

Every filter has a different static pressure at the working point. The working point is where the amount of the air flowing through the filter is sufficient to meet the requirement of the laminar flow.

The static pressure is expressed in inch of water column in the English units, a typical value would be 1", the SI unit for pressure is Pa(Pascal).

1" water column is around 250 Pa. Each filter has a data sheet (consult the manufacturer if this is not the case with your filter) where the static pressure at the working point is entered. Before the air enters the blower it is usually pre-filtered by a furnace filter around 1"(2.5cm) thick placed in front of the blower to protect it and the HEPA filter from big particles like dust and hairs. It can be assumed that the static pressure for this prefilter at the working point is around 0.2"(50 Pa)

According to Stamets (Paul Stamets and J.S.Chilton: The Mushroom Cultivator p. 347 ff) the air speed of the air flowing from the filter surface should be (at least) 100 feet per minute(fpm).(around 30 meter per minute or 0.5 meter per second). Determining the correct blower for a filter consists of several steps:

1. Find out the area of your filter by multiplying the width and the hight in feet (for instance the smallest reasonably usable filter would be 2ft x 1ft)
2ft x 1ft = 2 ft2

2. Multiply the required air speed(the one Stamets specifies, 100 ft/min) with the area of your filter
100 ft/min x 2 ft2 = 200 ft3/min

So 200 ft3/min(= cfm = "cubic feet per minute") is the amount of air your blower must deliver at the sum of the STATIC PRESSURE of the HEPA filter + prefilter.

NOTE: 1 cfm= 1.7m3/h

So if you use the above filter with 1"(250Pa) static pressure and a furnace prefilter with a static pressure of 0.2"(50Pa) your blower must deliver 200 cfm(340m3/h) of air at a static pressure of 1.2"(300Pa).


And as far as a blower goes like i said it does not need to match exact as this describes and not understanding that is what held me back for some time. Finding the correct blower

Each blower has a data sheet (consult the manufacturer if this is not the case with your blower) where the correlation between the volumetric flow and the static pressure is represented by a graph or table.

Here is such a set of curves for 4 blowers(numbered 1-4).
NOTE: Each model of a blower has his own characteristic curve. This chart shows the curves for 4 different particular models of axial duct blowers.
What you can clearly see is that the bigger the static pressure the less air the blower delivers, up to the maximum static pressure where the air output is zero.

Sometimes these data are presented in form of a table.

By now you know how much your blower must deliver and at which static pressure. In our example it was 340m3/h at 300Pa.
So what we do now is to go in this chart and find the value of 300Pa(=1.2") at the vertical axis. Then you move to the right until you reach 340m3/h.(=200cfm)
Now, ideally there should be a curve of a blower going exactly trough this point, but this is not always the case.
So we have to choose a blower that best approximates our requirements.
In most cases we should choose a stronger blower, if it's not too strong.
How strong is too strong? I'd say the blower shouldn't deliver more that 20% more air than we calculated, so in our case the strongest acceptable blower would be around 400m3/h.
In this example we have a blower that delivers 300m3/h(according to our calculation it should deliver 340m3/h though). This is a difference of mere 10%. The next stronger blower in this chart delivers 530m3/h at 300Pa, which is way too much.

In this case we go for the smaller(and cheaper) blower(Nr.4) instead of the much bigger one(Nr.1, which delivers 530m3/h at 300Pa), despite the fact that it's generally recommended to take a stronger one.

NOTE: This chart is only an example for a set of 4 particular blowers. The curves of the blowers available to you may look a bit different, but similar.
Usually, if you search long enough, you will be able to find a blower that exactly matches your HEPA.

The design in this pictorial uses an in-line centrifugal fan, another good option (actually the one most commonly used for flow hoods) is a squirrel cage blower (also called shaded pole blower).

You can get many blowers at ebay.com, often at much cheaper prices than if you bought them directly.
Ebay offers

It is important to contact the seller in advance and inquire about the exact characteristics of the blower beforehand, so you don't end up with a too weak blower.

When in doubt, head for the more powerful blower, you can still regulate it down if necessary with a variable speed controller/regulator:


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Offlineanontemp
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Re: flow hood - - filter questions [Re: tombosley8]
    #20335179 - 07/26/14 10:50 PM (9 years, 7 months ago)

I really want this Flanders filter, its huge size + low price. Here are its sticker specs.
resistance(*wg) : .33
test flow: 545 cfm
penetration: 0.00070%
filter dimension: 22~ x 44~ x 5.4
for $150

Now the only problem I can see on the manufacture website, is that its rated for 99.99% AT 0.3micron they also make the same model with different spec rated at 99.999% AT 0.3.

Does the 99.99 make this filter unusable for mycology work?

Also this model does not have any 'gasket material' ala the glue on the edges of the hepa filter. IS that required for mycology work?

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Offlineanontemp
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Re: flow hood - - filter questions [Re: anontemp]
    #20337760 - 07/27/14 01:15 PM (9 years, 7 months ago)

No one can advise me on the filter? Well I'm ordering it toight with my fan. Ill show you guys how it turns on next weekend

http://www.ebay.com/itm/220816146826?item=220816146826

and fan

http://www.ebay.com/itm/181398568515?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
200

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Re: flow hood - - filter questions [Re: anontemp]
    #20338072 - 07/27/14 02:03 PM (9 years, 7 months ago)

you want a filter that has a higher resistance at the test flow. I Think around 1" is good. I think you want the tested cfm to be the surface area in feet of the filter face x 100 fpm. so a 2x4 filter you would want 800 cfm at 1" static pressure or close. For a 2x2 you would want 400 cfm at 1" Static pressure.  A bit more cfm is better than less I believe. you want to get a blower that can handle the tested airflow of the filter. So for example, with a 2x2 filter with a testflow of 400 cfm @ 1" S.P. you need to look for a blower that shows it can deliver at least 400 cfm under 1" of pressure. Since you should use a prefilter you should also add 10-20% to the cfm to accommodate. The blower you listed looks good enough for most 2x2 filters I believe. But you should find a filter with higher resistance first


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Edited by tombosley8 (07/27/14 02:09 PM)

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Offlineanontemp
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Re: flow hood - - filter questions [Re: tombosley8]
    #20340250 - 07/27/14 09:34 PM (9 years, 7 months ago)

Yes that blower is more then good enough for what I'm trying to do.

However I just can't find anything but 24 x 24 hepa filters. I can find bigger ones but their not the specs you are suggesting.

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Re: flow hood - - filter questions [Re: anontemp]
    #20340507 - 07/27/14 10:32 PM (9 years, 7 months ago)

Quote:

anontemp said:
Yes that blower is more then good enough for what I'm trying to do.





That may just cut it for a 2'x4' filter with tested airflow around 800 cfm at 1" S.P. but remember i said more is better than less. It will def work for a 2x2 and i heard you can find good ones for cheap from filtera of all sizes... You just have to call em up during business hours. Keep the specs in mind I told (400 cfm at 1" for a 2x2; 600 cfm at 1" for a 2x3; and 800 cfm at 1" for a 2x4). If you get one with something close to those specs your set. Remeber to get a speed controller.  :cool:  :thumbup:

this tek really helped me build the hood http://www.shroomery.org/forums/showflat.php/Number/19798444 when you get there good luck


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Edited by tombosley8 (07/28/14 02:53 AM)

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Offlineanontemp
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Re: flow hood - - filter questions [Re: tombosley8]
    #20344687 - 07/28/14 09:48 PM (9 years, 7 months ago)

I have searched and read many threads, but none talk of the larger filters really and don't have good details.

Thanks for that, Ill check them out. Yeah I'v seen their 'dead' links around and couldn't figure out. I'll see what they have to say or just go with the FP guys


You right, I do need a better blower. I think I also figured out why these lower resistance filters wont work. I won't be able to get a real laminar flow AND the purity of the air filter. aka the air speed of laminar flow is too fast for the filter to clean the air. Though I still don't understand why they are marketed as laminar.

Now only need to figure out a plenum for this large blower. Is there any deigns that can be used to diffuse air? Like a board with holes between the blower (a plenum chamber?)

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Re: flow hood - - filter questions [Re: anontemp]
    #20344709 - 07/28/14 09:59 PM (9 years, 7 months ago)

:whathesaid: your on to something
I think you need a plenum at least twice the depth of the filter so the air has enough space to build on the back side of the filter with an even pressure.  With very large filters such as that (2x4) you may need a bit more hopefully someone can chime in here.


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Offlineanontemp
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Re: flow hood - - filter questions [Re: tombosley8]
    #20347827 - 07/29/14 04:53 PM (9 years, 7 months ago)

Yeah I really hope I get a response about the plenum chamber before I get the items. I don't really wanna go over 2ft depth box but if I have to.

Someone with some HVAC/plenum knowledge please help! What can and what cant I do inside this box. Will putting the blower on top with a 90degree turn into side channel into the box mess up plenum? (see this http://www.germfree.com/wp-content/uploads/bzairflow.gif

What about the 'standard' design with a air-baffle/board with holes inside separating the blower exhaust and back of filter? My logic says this should be fine as long as the holes are big enough not to induce more SP/back pressure (like inch holes atleast would be used).

I got the FP filter so I have a 48x24x5.8 / 1500cfm @ 1" s.p. I also got the next model up on the blower that they suggested 3/4hp instead of the 1/2hp dayton. 4 Speed / CFM @ 1.000-In.SP 1864-1776-1636-1474. Also a CFM meter is coming as well.

Edited by anontemp (07/29/14 04:54 PM)

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Re: flow hood - - filter questions [Re: anontemp]
    #20347973 - 07/29/14 05:20 PM (9 years, 7 months ago)

I wouldn't rely on the cfm meter. Try to get your flow as close to accurate with the blower and filter matched up first. Your probably going to need to hook that blower up on it's second highest setting (remember the 10-20% addition to cfm to accommodate for prefilter) and then use a bic lighter to judge the airflow. If it's too much just stack up prefilters or cover up part of the intake. I just put a peice of cardboard over my prefilter enough to slow air to laminar flow. I really think you would be fine with a 2 ft plenum (actually that's quite large {4x the filter depth} but it wouldn't hurt). You don't want the blower directed straight at the filter. Putting the blower on top of the filter box directed downward works great. Just cut a clean hole the size of your blower outtake, mount it and seal it on with silicone. Then you can create a box around your blower to apply your prefilter. PirateSwazey's flow hood build Is a good reference for how a hood should be designed.


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Offlineanontemp
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Re: flow hood - - filter questions [Re: tombosley8]
    #20348552 - 07/29/14 07:33 PM (9 years, 7 months ago)

I do appreciate the information. However again, every post you link is a 24x24 filter/tutorial and everything I'm trying to do is just side note(expand blabla measurement and it will work!)

Sure, I don't disagree, but seeing as I have yet to see a thread with pics or any real detailed information on larger filter. I'm left thinking,

I'm sure there's a better way AND I'm not so sure this is all going to 'just work' like these everyone on this site says. I'm imagining the space of a 14x14x8(1500cf) room being pushed down inside a 2x4x2 box with 16 cubic feet of space. All I see is turbulence hitting the filter. And in comparison a 7x7x8(400cf) 2x2x2 box with 8cf. So while box size spec matches the 'instructions', Im pushing 2/3 more air then the smaller boxes.

Edited by anontemp (07/29/14 07:36 PM)

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Re: flow hood - - filter questions [Re: anontemp]
    #20348962 - 07/29/14 09:34 PM (9 years, 7 months ago)

Quote:

anontemp said:
everything I'm trying to do is just side note(expand blabla measurement and it will work!)




umm... what?


Quote:

anontemp said:


Sure, I don't disagree, but seeing as I have yet to see a thread with pics or any real detailed information on larger filter. I'm left thinking,

I'm sure there's a better way AND I'm not so sure this is all going to 'just work' like these everyone on this site says. I'm imagining the space of a 14x14x8(1500cf) room being pushed down inside a 2x4x2 box with 16 cubic feet of space. All I see is turbulence hitting the filter. And in comparison a 7x7x8(400cf) 2x2x2 box with 8cf. So while box size spec matches the 'instructions', Im pushing 2/3 more air then the smaller boxes.




i think your over thinking that.    turbulence doesn't have to do with the cubic ft of the room your using. It will be more turbulant with a small plenum because the air doesn't have space to build on the back side of the filter with even pressure. I'm pretty sure you just need to put your blower as far back from the filter as possible and truly i really do think 2 ft plenum behind the filter is going to work fine.
here's somethin rr said about a 2x4
Quote:

RogerRabbit said:


For a 2 X 4 filter, go with a blower(not a fan) capable of delivering 800 cfm @ .8 to 1 inch of static pressure.  After installing the prefilter, if you need to slow down the flow, block off part of the intake.
RR


and one close to that size
Quote:

RogerRabbit said:
Get a blower in the 700 to 900 cfm range @ 1" w.c.

The math:

21" X 44" is 6.4 square feet.  (21X44)/144=6.4

You want 100 to 125 linear feet per minute flowing out from the filter, therefore in a perfect world with no resistance, you'd want a fan that could deliver 640 cfm(cubic feet per minute) at minimum and 800 cfm at the top end.  I always just wing it and add around ten percent or so to make up for ineffeciency and friction, etc.

Look at Grainger.com and find a squirrel cage blower that will deliver that kind of flow @ 1" static pressure.  A lot of motors rating only goes up to .8 wc, but consider that the same as 1" for our purposes.
RR Make the plenum as large as the filter is thick, or slightly more.  Position the fan so the intake faces towards the rear, away from the filter.  Hook up that motor on low speed.  If it still blows too hard, block off part of the intake with cardboard.

You'll know when the flow is right, because a bic lighter held six inches from the face of the filter will bend 45 to 90 degrees, but not blow out.  You can do a poor mans laminar flow test with a bic lighter too.  Move it all over the work space, and the flame should remain bent to the same angle, regardless of where you place it.

I'm jealous-that's three times the size flowhood I have.
RR 


that one's 6 years old but the only thing that he says differently now is 2" from your filter is where to test the flow
Quote:

RogerRabbit said:

Build the flow hood, leaving at least 8" of free space behind the filter.  This is the plenum where air from the blower will pressurize, thus placing an equal amount of air over the entire back surface of the filter.  This helps to achieve laminar flow out the front.

Place a lighter 2" away from the face of the filter.  It should bend over about 45 to 60 degrees, but not flicker or go out. It should also blow over the same amount no matter where around the face the filter you place it.  If there is too much flow, simply stack a couple of prefilters together to throttle it down or otherwise block off part of the intake.
RR



Though he was giving his advice on a 24x24x12 filter you can compare.
There are definitely varying opinions amongst trusted cultivators on the subject :
Quote:

Amanita virosa said:
the plenum should be two to two and a half times the thickness of the filter



and not a tc but :
Quote:

faceyneck said:

Quote:

but how deep is your plenum? JW, for my own research...I've got a massive HEPA, 2x4 = 8 sq feet of working area :rockon:




My plenum is much deeper than it needs to be, due to the size of furnace blowers. I think it's around 20" deep,  maybe more.

If you don't already know, plenum depth should be at least as deep as the filter is. For this reason, I actually plan on obtaining a nice Dayton blower once I can afford it, so that my box isn't so fucking massive. Space is not a luxury I currently possess.

:super:



here's a 2x4 flow hood with a filter 12" thick which requires a deeper plenum
Quote:

t3chnobily said:





and a 3x4
Quote:

drake89 said:



Tech- that's a nice build!


just so you get the idea


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Edited by tombosley8 (07/30/14 02:49 AM)

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