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Offlineeatplaydough
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Will this HEPA work? Can I make it work by stacking prefilters?
    #24257264 - 04/19/17 12:52 PM (7 years, 8 months ago)

I purchased this filter and I now realize it may not have enough resistance (only .56 W.G. at 365cfm).

http://www.ebay.com/itm/302273342434?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Not sure if that link will work but the filter is 1.5 x 2 ft, so at 100ft/min, i'll need to get 300cfm flowing through the filter for laminar flow. BUT at this flow rate the static pressure caused by the HEPA will only be around .5 W.G.

Do I actually need atleast .8 W.G. in my plenum to achieve laminar flow? Could I do this by "stacking" three .2 W.G. resistance furnace prefilters infront of my Hepa?

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Offlinemushpunx
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: eatplaydough]
    #24257657 - 04/19/17 03:56 PM (7 years, 8 months ago)



You know the numbers on the filter are confusing. Ive been told before that the sp listed on every filter is what they tested at when using a particle counter to confirm its quality.

That looks almost identical to the filter I used, mine came from Fungi Perfecti, I'd have to take it out of the hood to see if its Flanders though.

For that filter, you will need at least a 6" deep plenum but I built a 10 or 12" deep one.
You'll need a blower that pushes 300CFM @ 1.2 SP at least.

My blower is a Dayton, model 1TDT2. 549CFM @ Free air. I no longer have the specs but it pushes 360CFM @ .8SP, so its right above 300CFM @ 1-1.2SP (.2 SP added for the prefilter).

So if you get that filter, and get the Dayton blower I have it will match very well. They sell this blower on FP but you can find it much cheaper, I paid 80$ , with free shipping.

18 x 24 turned out to be a great size hood for me. Its essentially the same as the Series 11 flow hood on Fungi Perfecti (RR uses the series 1 in his videos , 12 x 24) , but I saved money by building it myself.


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AMU Q&A

Edited by mushpunx (04/19/17 03:58 PM)

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Offlineeatplaydough
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: mushpunx]
    #24258289 - 04/19/17 08:36 PM (7 years, 8 months ago)

Sorry, not quite sure what you mean. You think the .5 W.G. resistance at 100 feet per min will work for laminar flow, or you think their measurement is inaccurate?

Also, besides the dimensions being the same, why do you assume my HEPA would behave just like yours? Is the manufacturing of these filters that standard?

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Invisiblec10h12n2o
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: eatplaydough]
    #24258380 - 04/19/17 09:25 PM (7 years, 8 months ago)

i was under the impression that the FP filters all have a static pressure around 0.8" to 1.0", mine did

im not sure about this, this is exactly why i got mine from FP so that id be sure it was ideal for a laminar FH

i have seen people say that ideally you want a fair amount of pressure in the plenum, which is why they are built to have around 1" , so that it can equalize the pressure across the surface of the filter

on the other hand, i have seen people use filters from ebay that were less than ideal (like the 11" wide kind) where people would really struggle to get any pressure at all built up, and they seem to meet their goals with it

so i am not sure, only repeating what ive heard others say.

also, if i understand correctly, adding filters will increase the resistance on the blower, but i dont think stacking them will increase pressure in the plenum, it would probably decrease it.... but i totally cheated in math class, so there are definitely more knowledgeable members about the physics haha


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C10's Agar Guide + Tips and Tricks | c10's Flow Hood Build Guide


"Partial knowledge is more triumphant than complete knowledge; it takes things to be simpler than they are, and so makes its theory more popular and convincing."

"Convictions are more dangerous enemies of truth than lies"
― Friedrich Nietzsche

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Invisiblelaughingdog
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: eatplaydough]
    #24258725 - 04/20/17 01:07 AM (7 years, 8 months ago)

FP filters are "down to .3 microns with a guaranteed efficiency of 99.99%"
the ebay filter is EFFICIENCY RATING: 99.97%
I have heard this actually makes a difference

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Invisiblec10h12n2o
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: laughingdog]
    #24258770 - 04/20/17 01:52 AM (7 years, 8 months ago)

it did to me... this is one of the reasons i spent the extra $ for the FP filter


--------------------

C10's Agar Guide + Tips and Tricks | c10's Flow Hood Build Guide


"Partial knowledge is more triumphant than complete knowledge; it takes things to be simpler than they are, and so makes its theory more popular and convincing."

"Convictions are more dangerous enemies of truth than lies"
― Friedrich Nietzsche

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Offlinemushpunx
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: c10h12n2o]
    #24258951 - 04/20/17 06:20 AM (7 years, 8 months ago)

"those 2" filters can achieve laminar flow, but the life time is way shorter than a regular 6" filter, and even less than the 12".

the sp that is listed on them, is what they are tested at with a particle counter, and the corresponding cfm coming out of the filter.

Meaning that at X.X" sp you get XXX cfm

because we are technically repurposing these filters, those number have no use to us.

Versicolor actually explained this to me.

From versicolor:
Quote:

When I say a filter doesn't have a specific static pressure, I mean the static pressure is in the plenum. 1"wg could be obtained with any filter, with the right blower.
The SP required for laminar flow is usually somewhere between 0.8"&1.2"wg.
The key is to maintain a flow rate of around 100cfm per ft2 face area, while maintaining the 1"wg plenum pressure.
The flow rate is the difference with thicker filters - it will be slightly higher, as it has (usually) less resistance.
But it will be laminar, which is the important part. You just have to get the charts for the blower, and match it to the specs of the filter. "



This is an excerpt from a conversation I had with another member when I was building my flow cabinet.
He was trying to explain how you can reach laminar flow with a 12" deep filter


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Edited by mushpunx (04/20/17 06:39 AM)

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Offlinemushpunx
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Re: Will this HEPA work? Can I make it work by stacking prefilters? [Re: mushpunx] * 1
    #24258979 - 04/20/17 06:36 AM (7 years, 8 months ago)




I am fairly confident that with that 18" x 24" x 5 7/8" HEPA you are looking at you will achieve laminar flow with a blower that pushes near 300CFM @ 1" SP and a Plenum between 6 - 12" behind it.




That being said though, I wouldn't buy that filter from there for 200.

Fungi Perfecti (where I bought my filter, I have an 18 x 24) sells an 18 x 24" HEPA for 200$ right now. It was shipped with wooden boards protecting the super delicate filter faces.. Seriously just a slight tap with crush the pins.. So it would make more sense to buy it from a store if you're paying the same price.
Its a fair price.


I would match it to a Dayton model 1TDT2 549CFM blower (don't but it from FP you can get it much cheaper).

Those are the two parts they use in the " Series 2 " FH they sell for 1000$.


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Amateur Mycologists United
AMU Q&A

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