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Help me troubleshoot my flow hood
    #26989010 - 10/16/20 08:56 PM (8 days, 6 hours ago)

I've recently built a new 2x4 flow hood. Just got it finished yesterday night, but I'm having an issue with it. I thought I matched up the filter and the blower correctly, and went over my math a dozen times. However, when I turn the hood on, the air flow coming out is minimal. The blower is clearly working, but there is barely any actual flow coming out. There's a couple spots that flow harder than the others, but for the most part, there is hardly any flow.

The blower I have is the Dayton 1TDU2. https://www.grainger.com/product/DAYTON-OEM-Blower-1TDU2

The cfm is 1202 at 0 in

The filter is rated for 1000 cfm at 125 fpm, which would be more than enough for the 1202 cfm of the blower and the 100 fpm needed for laminar flow. Accounting for the prefilter, I figured this filter/blower matchup would be perfect.

This is the filter
https://www.globalindustrial.com/p/hvac/filters/HEPA-Filters/koch-filter-9999-biomax-hepa-24-inch-w-x-48-inch-h-x-5-7-8-inch-d

I feel like I did a good job building the damn thing, so I'm confused on what is happening. I did notice that there is not a perfect seal on the back as I can feel slight air currents coming out of two spots on the seams of the wood, so I'm going to seal those up better and hope that fixes it, but I'm not sure, as the flow coming out of the hood is very weak.

What do y'all think? Any advice on how I can fix this, or does it seem like either the filter or the blower are not functioning properly?


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OfflineForrester
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Re: Help me troubleshoot my flow hood [Re: mind.at.large] * 1
    #26989578 - 10/17/20 06:52 AM (7 days, 20 hours ago)

I'm not an expert on the math of matching blowers to filters, but any leaks in the box are going to have a pretty big impact.  I was going to say your box might have leaks, but then I read on and you've already confirmed it does.

I would silicon all seams of the box to start.  And make sure you have a good seal where the blower itself attaches. 

And maybe post some pics?  You might need a baffle to even out the airflow if your blower is blowing directly on the filter.


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Re: Help me troubleshoot my flow hood [Re: Forrester]
    #26989620 - 10/17/20 08:07 AM (7 days, 19 hours ago)

You will rarely feel much air in front of your flowhood.  Do the lighter test.  Hold a lighter or match in front of the hood, right up near the filter.  The flame should bend over between 45 and 90 degrees, but not go out.

If it passes the test, you're good.
RR


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Re: Help me troubleshoot my flow hood [Re: RogerRabbit]
    #26989647 - 10/17/20 08:40 AM (7 days, 19 hours ago)

Fix the air leaks. You won’t really feel a lot of air blowing out of your filter. I looked at the specs of the blower and filter, and the blower is just barely enough for that filter. Your filter is 1000cfm@1.5” wg. At 1.5” wg that blower only puts out about 800cfm. Now 800cfm is still 100 FPM@filter face, which is good, but you don’t have a lot of wiggle room as your filter starts to load with dirt, or to add a prefilter. Are you running a pre filter?


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Re: Help me troubleshoot my flow hood [Re: RoscoeReturns]
    #26990065 - 10/17/20 02:58 PM (7 days, 12 hours ago)

Thanks for the advice y’all! First things first, I’ll seal up all the edges and leaks today and see if that helps. I’ll try to remember to take pics and upload them.

In terms of filter/blower matchup, yeah I noticed that the CFM of the blower at the resistance of the filter was just near 800, which yeah is cutting it real close, but should be fine for now haha. I would have chosen a different blower, but I had purchased the blower and a different filter at the same time, which matched up with some excess flow, but then the wonderful people at Fungi Perfecti decided to take my money, and then tell me that they don’t have the filter in stock and it would take over a month to get, after charging me $750. Fuckin assholes...

So I scrounged around for a different filter that would fit the blower I had already purchased, and this one seemed to match up the best, albeit cutting the CFMs close.

But yeah I’ll do some sealing, do the lighter test, and report back.


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26990704 - 10/17/20 11:15 PM (7 days, 4 hours ago)

Update:



I've siliconed every crack and crevice on that thing. It's airtight, at least from what I can feel. The flow has definitely increased and actually feels like it should be. The lighter test seems to show a good flow, and I've attached a pic.

The biggest issue now is how uneven the flow is. In two spots, the flow is definitely too strong that it puts out the flame. In another spot, there is barely any flow. I figured that the problem was that the air was not being distributed equally throughout the box, even though the blower is attached at the back of the box.

I started cutting a baffle to attach to it, when I realized I could just check it by flipping the filter. I did that and then turned it on, and the high flow/dead spot was in the same spot relative to the change in filter placement. I'm assuming this means the issue lies with the filter itself, which kind of bugs me as this thing was damn expensive, but does anyone else have an idea on what it could be?

Where the flow is too strong is right in the middle of the filter, and it looks weird. The paper part between the fins is a little more pressed out compared to the others. It's hard to explain but I've included a picture of it.

Also, the resistance of this filter is actually different than what was advertised, which is really annoying, but means that the blower is more than sufficient for this filter.

This is obviously very frustrating as I've spent a hefty amount of money and time building this thing. I have some sterilized grains already waiting so I was really hoping that it would be completed by yesterday, but unfortunately this is how these things go sometimes. I'm planning on testing some agar plates over the areas that seem alright so I can maybe use a section of it to get work done, while I figure out the issue, but I'm wondering if my problem is isolated to the filter itself, and if I should go down the path looking for a refund. What do y'all think?


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26990987 - 10/18/20 06:27 AM (6 days, 21 hours ago)

Hmmm... yeah that is frustrating. 

Given the "too much flow" area is right in the middle where the blower is, I would still try a baffle first, to spread out the air more away from the center.  At least before going through all the hassle trying to get your money back for the filter if something is wrong with it!


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Re: Help me troubleshoot my flow hood [Re: Forrester]
    #26991194 - 10/18/20 11:20 AM (6 days, 16 hours ago)

Yeah that’s what I was thinking, so I might just install a baffle anyways, but let me see if I can explain it better.

The high flow area was in the center, about two inches from the bottom, which totally made me think that was because that’s where the flow is concentrated the most. So I took the filter out and flipped it. Now the high flow area is still in the middle, but it’s about two inches from the top, so essentially it’s in the same area of the filter, relative to flipping the filter. This means that the high flow area isn’t because of uneven distribution of flow, but has something to do with the filter construction.


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26991207 - 10/18/20 11:31 AM (6 days, 16 hours ago)

Ah ok, I see what you mean.  That would definitely point to a filter issue... although it couldn't hurt to try.  Hopefully you can get a replacement!


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Have some medicinal mushrooms and want to get the most out of them?  Try this double extraction method.


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Re: Help me troubleshoot my flow hood [Re: Forrester]
    #26991245 - 10/18/20 12:13 PM (6 days, 15 hours ago)

Yeah... I’ve just emailed the company I got it from, so hopefully will hear back tomorrow, but in the mean time, I’ll just install that baffle and hope for the best.

Thanks for the help forrester


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26994505 - 10/20/20 02:44 PM (4 days, 13 hours ago)

So I'm pretty confident that the issue is with the filter. The flow is not even, independent of the filter's orientation, and with the baffle installed. I'm currently going back and forth with the supplier/manufacturer on getting a replacement. The manufacturer, Koch Filters, swears that it gets tested to perfection before ever leaving the warehouse, but hopefully I can prove to them that their product is in fact defective, and that even they can make mistakes sometimes.

Anyways, what I'm wondering, is while I wait around trying to figure out this issue, should I attempt any sterile work in front of this hood? It is a 4 ft wide filter, and one half (2 ft) seems to flow well. The whole half of that section passes the lighter test. The other half is the one with the problem, ie. too much flow, too little flow in certain areas. Would it be worth it of me to get a flowmeter to measure certain areas to make sure they are within that laminar flow range? Or is the lighter test good enough?

Would it be stupid of me to trust the good half to do work in front of or should I just wait for a replacement? Will the high flow area in the middle cause eddies that would ruin the laminar flow of the good section? I've worked in front of a small flow hood before, so I feel confident in my ability to work well in a 2 ft section, I just don't know if it's a dumb idea.

I'll be placing some fresh agar plates in front of certain areas of the filter to see just how clean it is, but want to know what y'all think!

:heart:


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26994592 - 10/20/20 03:40 PM (4 days, 12 hours ago)

I'd probably go for it!  Worst thing happens is a little wasted supplies :shrug:


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Have some medicinal mushrooms and want to get the most out of them?  Try this double extraction method.


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Re: Help me troubleshoot my flow hood [Re: Forrester]
    #26994752 - 10/20/20 04:54 PM (4 days, 10 hours ago)

Just what I wanted to hear! Haha thanks dude!


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26996113 - 10/21/20 12:32 PM (3 days, 15 hours ago)

Ok, so I did some agar transfers in front of "good" section of the hood so we will see how it turns out.

The problem I am having now is with the engineers and customer service at Koch Filters. I've explained the problem, and it seems like their responses have been, "well, we check everything before it leaves our warehouse, so there's no way we could make a mistake." The answer I just got from email was that air flow will not be consistent across the face of any filter. This seems ridiculous to me, as isn't the point of laminar flow is that it stays consistent? Areas of higher flow or lower flow will create eddies and lead to turbulent flow, ruining the laminar flow that I am after. Please correct me if I'm wrong, or if y'all have flow hoods that don't blow consistently even across the face. I have used flow hoods before, and have noticed a very slight discrepancy between areas of flow, but this one is very obvious. I purchased a flowmeter online and it will be here tomorrow so I can provide actual data on how much flow is coming out.


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Re: Help me troubleshoot my flow hood [Re: mind.at.large]
    #26997084 - 10/21/20 11:58 PM (3 days, 3 hours ago)

How deep is your plenum? the purpose of the plenum is to build up air pressure inside the box before it presses evenly through the filter. with enough pressure you get that even laminar flow.

That build up of paper between the fins does look a little odd..


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Re: Help me troubleshoot my flow hood [Re: deadmandave]
    #26997101 - 10/22/20 12:15 AM (3 days, 3 hours ago)

I can't remember off the top of my head exactly, but I'm pretty sure the plenum is near 20", which should be plenty.

I agree that the one section of paper looks off, and it just so happens to be the same area that has too high of flow sooo...

I'm actually receiving a new filter so yay!! I've been bugging the people at Koch Filters enough that I think they just gave up and said ship him another haha. The squeaky wheel gets the grease!!


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