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GTEED
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Flowhood items. Advice so far.
#27084333 - 12/11/20 04:58 PM (3 years, 1 month ago) |
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Alright so here are my two choices I plan on going with. For building myself a flowhood.
option 1- Damn filters 24x24x6 99.99% .79"W.G resistance 700CFM flow rate https://damnfilters.com/collections/hepa-and-other-high-efficiency-filters/products/hepa-filter-24-x-24-x-6-700-cfm-99-99-particle-board
option 2- Earthstongue 24x24x6 99.99% .9 W.G 625CFM @ 1" https://earthstongue.com/product/24_x_24_x_6_HEPA_FILTER_REPLACEMENT
Prefilter - Filtrete 1500 Ultra Allergen 12x12x1 https://www.amazon.com/Filtrete-Healthy-Allergen-Reduction-Furnace/dp/B00TUDHV8C
(assuming this filter is .21 static pressure - according to https://www.iallergy.com/pages/compare-3m-filtrete-filters)
Plywood - 3/4-in Birch Plywood, 4' x 8' 5ply
All I need now is a blower that will work with the above items. (Wondering if Dayton 1TDT8 would be a good fit. - https://images-na.ssl-images-amazon.com/images/I/71XMM5KjJ7L.pdf https://www.amazon.com/Dayton-1TDT8-Blower-115V-3-30/dp/B000TK3ZM6)
Does anyone have any suggestions for me so far?
Edited by GTEED (12/11/20 09:52 PM)
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FungusFreedom
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Re: Flowhood items. Advice so far. [Re: GTEED]
#27084423 - 12/11/20 05:46 PM (3 years, 1 month ago) |
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Do you plan on using a pre filter? It will prolong the life of your hepa so probably a good idea. If so add 1.2 to your resistance. For the second cheaper option that puts you at about 1. For the 24x24 you need 400cfm. According to the 1tdt8 graph that puts you very close maybe just a tad shy. I have an 18x24 and that is the blower I went with. I would check the next stronger one to see if it is better.
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GTEED
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Yes, I plan on using one of the prefilters I listed above. hmm I wonder if I should just go with a 18x24x6 then. I'm having a hard time for some reason figuring all this out :P Does anyone have any experience with Damn filters or earthstounge? I'm wondering how the quality is.
Edited by GTEED (12/11/20 09:49 PM)
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Groo
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Re: Flowhood items. Advice so far. [Re: GTEED] 1
#27084797 - 12/11/20 10:20 PM (3 years, 1 month ago) |
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Find a fan that will get you MORE than 100 on its highest setting if possible. So try to find a 2 speed fan if possible. with the low speet matchign this one and the high speed giving you 150-200 cfm if its not over the limit of the filter.
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Groo
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Re: Flowhood items. Advice so far. [Re: Groo] 1
#27084801 - 12/11/20 10:25 PM (3 years, 1 month ago) |
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Edited by Groo (12/11/20 10:29 PM)
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GTEED
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Re: Flowhood items. Advice so far. [Re: Groo]
#27084841 - 12/11/20 11:31 PM (3 years, 1 month ago) |
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with this filter - https://earthstongue.com/product/24x12x6-HEPA-FILTER-REPLACEMENT
does anyone what it means by 625cfm @ 1"? is that stating that i need a blower that can provide that?
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FungusFreedom
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Re: Flowhood items. Advice so far. [Re: GTEED]
#27084851 - 12/11/20 11:48 PM (3 years, 1 month ago) |
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I think that may be referring to the airflow capacity at the initial resistance 1". You can use the Dayton 1TDU1 with option 1 and no prefilter and it would be about perfect I think. The spec sheet says 500cfm at .8" forthat blower.
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GTEED
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well what is confusing about the Damn filter 24x24x6 is if you look at the data sheet for the filters it says its .79w.g @ 175FPM. Does that make a difference at all about the static pressure of the filter? would the static pressure be the same if it was 150FPM for example? Would .79w.g just be the static pressure overall at any speeds?
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FungusFreedom
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Re: Flowhood items. Advice so far. [Re: GTEED]
#27084929 - 12/12/20 01:30 AM (3 years, 1 month ago) |
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I am guessing here, but I think that reads as we tested it at 175fpm and the resistance initially was .79.
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sandman420
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The static pressure absolutely changes when the airflow changes. More cfm pumped into a filter will increase the resistance.
So 0.79" was the resistance at the test speed of 175 fpm (700 cfm through a 4 sq foot filter is 175 fpm flow rate)
At 100 fpm the resistance will be considerably lower, it is not linear but a close enough is good enough here.
So the "damn filter" is likely more something like 0.45" wg at 100 fpm. With the prefilter you are looking at 0.65" wg total.
Look what the blower runs at that speed, get one that does about 400 cfm @ 0.65" wg
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Groo
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Re: Flowhood items. Advice so far. [Re: sandman420]
#27085224 - 12/12/20 08:23 AM (3 years, 1 month ago) |
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Keep in mind he was looking at 2 filters 1 with res .9 and 1 .75
Please refer me to where you read about wg resistance i waa read what you are saying about.
got it but theres no math formula any
Edited by Groo (12/12/20 10:51 AM)
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sandman420
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Re: Flowhood items. Advice so far. [Re: Groo]
#27085237 - 12/12/20 08:31 AM (3 years, 1 month ago) |
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wg same meaning as sp. Wg means inches water gauge also sometimes wc inches water column all same shit. the measurement of static pressure we are using.
Refer to what, that static pressure changes as airflow changes?
Well I can show you things like this

and this
https://www.mtlfab.com/media/SF4000_Resitance_Curve99.pdf
or you can use your mind and think about blowing in a straw. It's easy to blow a small amount of air through a straw lightly, but you can blow so hard that your cheeks hurt because you are trying to force more air than can fit at once increasing the static pressure, ie the "wg.
Edited by sandman420 (12/12/20 08:33 AM)
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RoscoeReturns
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Re: Flowhood items. Advice so far. [Re: Groo]
#27085426 - 12/12/20 10:20 AM (3 years, 1 month ago) |
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But pressure changes with the square of airflow. Fan law. #2 can be used to approximate sp.
Using that “damn filter” example:
(cfm2/cfm1)^2 * SP1 = SP2
(400/750)^2 * 0.79 = SP2
(0.53)^2 * 0.79 = SP2
0.28 * 0.79 = SP2
0.22= SP2
Unfortunately even that won’t be quite right as the curve for an actual filter won’t follow those rules at very low, or very high airflow. The 100fpm we look for to achieve laminar flow, is actually a fairly low flow rate, so the actual sp is likely a bit higher than calculated. Filter manufacturers will typically publish airflow vs pressure curves similar to the one sandman posted for a particular type of filter. The listed static pressure on the filter label is the actual measured pressure for that individual filter as tested. They don’t test each filter at multiple air flows, but the pressure curves they publish are pretty close.
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GTEED
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Ok, so I have decided to rule out the earthstongue filters because the static pressure is higher (.9 w.g) which means I will need a big 1/4hp blower the 1TDU2. Now going with the "damn filter" 24x24x6 based on the logic you brought up sandman420 - 400cfm @ .65 w.g I believe this to be better.
Using the "damn filter" 24x24x6 with .65 w.g I believe the two best choices for a blower would be the 1TDT7 or 1TDT8. Here are the specs on these two.

From what I am seeing the 1TDT8 is a little high on the CFM's, but could I use a router speed controller to adjust to get laminar flow by using a lighter test and get 100cfm showing using an Anemometer?
Which one would you guys recommend? 1TDT7 or 1TDT8? or am all wrong and need some other blower? One I am not aware of for this 400cfm @ .65 w.g recommendation?
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RoscoeReturns
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Re: Flowhood items. Advice so far. [Re: GTEED]
#27086043 - 12/12/20 04:29 PM (3 years, 1 month ago) |
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Not all blowers are suitable for use with a speed control. Make sure those are before assuming you can.
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sandman420
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Just don't use a speed controller at all on a squirrel cage blower. It can work on some particular ones, and other for a while, but it can be a fire hazard I burned up a speed controller once! Totally let the smoke out. You can block part of the intake to control the airflow with strips of gorilla duct tape across the intake opening if it is not too much of a change you need.
Looks like you could go with the dt7 and not speed control it and be in laminar flow speed range.
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GTEED
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That's helpful to know. Thank you.
Was looking to see if any DIY build plans were out there and found this website. http://www.sporetradingpost.com/flow_hood_equipment.htm
They are also selling filters up to 24x24x6 and it has a:
"All-Purpose Blower--549 CFM Free Air Delivery 115V/60Hz, 549 CFM free air delivery, 360 CFM at .8" static pressure."
that it states will work with any of their filters they are selling. Does this seem correct? worth my time and money going this route? or should I just try out the "Damn filter" brand and try the 1TDT7?
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sandman420
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Re: Flowhood items. Advice so far. [Re: GTEED]
#27086113 - 12/12/20 05:13 PM (3 years, 1 month ago) |
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I'm pretty sure that blower they are selling is just a 1tdt7 and they very slightly rounded the numbers to make it less obvious. Wherever the price is right I reckon.
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Eclipse3130
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Re: Flowhood items. Advice so far. [Re: sandman420]
#27086161 - 12/12/20 05:43 PM (3 years, 1 month ago) |
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Why not just buy a pre-made ready to go 2x4. They're only about $1000 shipped brand new, save time and money
-------------------- "In The Material World One seeks retirement and grows Old In The Magical World One seeks Enlightenment and grows Wiser In The Miraculous World One seeks nothing and grows Lighter As we all tread the Homeward Path we will explore many Realms And one day... we will all Realize that all experiences are Simply Different ways in which The All-That Is Perceives Itself"
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CocaineBuffet
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Re: Flowhood items. Advice so far. [Re: Eclipse3130]
#27086263 - 12/12/20 06:42 PM (3 years, 1 month ago) |
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Quote:
Eclipse3130 said: Why not just buy a pre-made ready to go 2x4. They're only about $1000 shipped brand new, save time and money
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TheBoJim
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why not just get a filter and a blower that others have used and are proven to work instead of figuring out yourself?
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FungusFreedom
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Re: Flowhood items. Advice so far. [Re: TheBoJim]
#27086470 - 12/12/20 10:06 PM (3 years, 1 month ago) |
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Most of the write ups I saw for 24x24 used a 1tdu2 which is apparently way way more than necessary. It must be a fairly wide range that will work though, because I am using a 1tdt8 blowing just shy of 400cfm at 1"wg, where 1"wg is the max resistance for my 18x24 filter, and I still get nice even flow. Probably just more than the 100fpm you need. As long as it stays laminar I can't see having a little more airflow as a terrible thing.
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GTEED
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Re: Flowhood items. Advice so far. [Re: TheBoJim]
#27086494 - 12/12/20 10:56 PM (3 years, 1 month ago) |
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well, I would love to know which filters/blowers (expecially filters) others are using. Do you have any links or any of the specifics TheBoJim?
Yeah FungusFreedom, If I were to go with the earthtougue filter I posted above the 1tdu2 would work. My only concern with doing this is it would cost me $109 dollars more for that blower.
So many variables. After I get all this figured out and built I'm considering making a tek that has up to date specifics on which filter and blower people should buy if they are looking to make whichever size flow hood I make.
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TheBoJim
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Re: Flowhood items. Advice so far. [Re: GTEED]
#27086503 - 12/12/20 11:14 PM (3 years, 1 month ago) |
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Quote:
GTEED said: well, I would love to know which filters/blowers (expecially filters) others are using. Do you have any links or any of the specifics TheBoJim?
i am just beginning my flow hood research and know almost nothing, so that was more of a question then a suggestion. i assumed with all the people here that have made hoods there would be a ton of info to go to.
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Eclipse3130
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Quote:
CocaineBuffet said:
Quote:
Eclipse3130 said: Why not just buy a pre-made ready to go 2x4. They're only about $1000 shipped brand new, save time and money

If you tried to build a 24x48 Flowhood it would cost quite a bit in parts, plus however long it might take you to build it. Time is money, and it's a lot better than buying a FungiPerfecti one for $3000 just a recommendation if you want to skip the building process and want one professionally made and delivered.
-------------------- "In The Material World One seeks retirement and grows Old In The Magical World One seeks Enlightenment and grows Wiser In The Miraculous World One seeks nothing and grows Lighter As we all tread the Homeward Path we will explore many Realms And one day... we will all Realize that all experiences are Simply Different ways in which The All-That Is Perceives Itself"
Edited by Eclipse3130 (12/12/20 11:32 PM)
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Groo
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I have a 36x72 and a 24 24... Its not wide enough and I find its a bit too tall.
I wish I had found a good deal in ebay like i did that 24 high capacity. I kept looking at 18x 38 or 24x36 or 2430.
Cocaine please tell us why you seem to think teh FFUs are shit. I agree but I want to see why you say.
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GTEED
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Re: Flowhood items. Advice so far. [Re: Groo]
#27086833 - 12/13/20 07:19 AM (3 years, 1 month ago) |
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Quote:
TheBoJim said:
Quote:
GTEED said: well, I would love to know which filters/blowers (expecially filters) others are using. Do you have any links or any of the specifics TheBoJim?
i am just beginning my flow hood research and know almost nothing, so that was more of a question then a suggestion. i assumed with all the people here that have made hoods there would be a ton of info to go to.
Ah yeah i cannot seem to find any specific filters anyone has used. Usually if they wrote what filter in thier post along with a link the link usually ended up being a dead end in one way or another. (no longer operating sites, ect)
I know i could use Fungi perfect.com, earthtounge.com, or mushroompatch.com and buy their filters and the blowers they sell I guess. I would prob be better off with fungi perfect. Im guessing they have been in business longer and would have it figured out what works.
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RoscoeReturns
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Re: Flowhood items. Advice so far. [Re: Groo]
#27087026 - 12/13/20 09:38 AM (3 years, 1 month ago) |
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Quote:
Groo said:
Cocaine please tell us why you seem to think teh FFUs are shit. I agree but I want to see why you say.
Not cocaine, but I’ll chime in on why FFUs are shit for this application. They use a 3” mini pleat filter and usually a centrifugal or inline duct type fan. This combo is not great at creating laminar flow. They do a great job of cleaning the air, and in their designed application that is all that is needed. They work by reducing the number of particles/contaminants in the airstream. This dilution works great in the ceiling of a clean room. Typically these are too far away from critical sites to be able to maintain laminar flow anyway, so it’s not a concern. In our application we not only want clean air, but also laminar flow to prevent contaminants on our hands/tools/supplies from being reintroduced onto sterile media via turbulent flow. FFUs are not good at creating this environment. They do work for some people. People who clean and sanitize their tools and have good sterile technique can get away with the low particle airflow the FFUs provide, but in any critical application I never see FFUs used in this manner. FFUs to dilute the particle burden in the room, but true LF hoods at the point sterility is needed.
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