|
Post by renesis on May 5, 2009 20:39:01 GMT -5
Hey everyone, So I decided to build my own flowhood after seeing several builds. I completed the first step today by acquiring the HEPA filter. I will update this thread as I progress so you all can see exactly how I build the flowhood and why I decide to do things the way I do. Hopefully someone else can benefit from this build, and hopefully others can offer my advice as I build it! So, step one was acquiring the HEPA. I managed to find locally a 24" x 12" x 6" - 99.99% Efficiency @ 0.3 micron, and aluminum housing with rubber gasket. Pictured here: Next, of course is to find the right blower to match to the filter. Then, the build of the frame. I've got access to a large supply of wood of all sorts of sizes. So hopefully I'll be able to find some good pieces. Wish me luck!
|
|
|
Post by sdeering on May 5, 2009 21:16:45 GMT -5
Not to rain on your parade. I biult one of these years ago for my hoby tissue culturing. Worked OK but was a pain to use. If it was in the house it might be better but takes up quite a bit of room. I use a tall seed flat dome with a door cut in the side. I get similar or better contamination rates using the dome. If one is used more full time it may be more practical for me anyways.
Looks like you are starting off with a good filter and have a very nice selection of wood to chose from though.
Are you going to use a pre filter arangement? I used an old furnace blower for air movement, and two layers of furnace filters for the pre.
Stephen
|
|
|
Post by renesis on May 5, 2009 21:28:20 GMT -5
Not at all, any feedback is good at this point!
I will be using it indoors, and am hoping I can get it sealed up well. I am going to go with a couple of the better quality furnace pre-filters to save the HEPA. Also will be sealing up the wood to make sure nothing sits within the microscopic scratches and to make it easier to clean, and work without worry of getting it wet.
Still haven't figured out which blower to use, all I've really found is that the final airflow should be around 0.5 m/s.
|
|
|
Post by lloyd on May 5, 2009 22:40:20 GMT -5
Tom posted a thread for his flow hood with some useful links about fans and filters. I use a plastic bin for a glove box. I use ppm and only get contamination from seeds or plants. I don't seem to get contamination from the air. I still want to make a laminar flow hood one day.
|
|
|
Post by renesis on May 6, 2009 7:04:37 GMT -5
Hey lloyd,
I did see that thread, unfortunately the pictures aren't up anymore. Hopefully Tom will step in and voice his opinions on how its worked out after having it for some time.
I also seemed to do just fine in my glovebox, I had just 1 contaminated (so far at least) out of 8 jars, and that one appeared to come out of the flower bud. This is using 1mL/L of ppm as well. But, I guess this is one of those things that I just wanted to do - because I can. Also it will be nice having a proper bench to work with with some more room than my current plastic box.
Thanks! Appreciate all the input!
|
|
|
Post by lloyd on May 6, 2009 17:36:04 GMT -5
Post all your building plans, I want to build my own someday.
|
|
|
Post by renesis on May 11, 2009 14:51:06 GMT -5
An update: Ordered the blower motor today - Its quite a bit more powerful than I need, but I figure I can down-regulate a lot easier than buying one too small. Its rated for 540 CFM free air. Should arrive in a week or so. $104 CDN Shipped.
|
|
|
Post by lloyd on May 11, 2009 18:46:34 GMT -5
It's probaby a synchronous motor which means the speed might be tied to the 60 hz power frequency, thus very hard to regulate. You could just use a mechanical bypass to lower the delivered flow.
|
|
|
Post by renesis on May 12, 2009 9:18:41 GMT -5
lloyd,
Yes, I believe it is a synchronous motor. I was thinking of doing a mechanical bypass - just a vent between the blower and the HEPA - either to open air or feeding back into between the blower and the pre-filter. My only problem with this, (and only in theory), is that having a low pressure area before the HEPA might disrupt the flow through the filter.
I was in the understanding that a fan control dimmer would work? I will look into this one a bit more.
|
|
|
Post by lloyd on May 12, 2009 16:18:57 GMT -5
Fan control dimmers would not work for synchronous motors as far as I am aware. You could use a pressure pop-off valve that should not disrupt the flow.
|
|
|
Post by sdeering on May 12, 2009 19:59:47 GMT -5
Ya the dimmer wont work. The motor may have separate windings for different speeds. Your filter will have quite a bit of pressure drop you will most likely need nothing, I would use a device that restricts the inlet on the suction side that will reduce your current draw as well.
|
|
|
Post by renesis on May 12, 2009 21:49:32 GMT -5
Hmm... good call sdeering - that seems like a good alternative. Maybe a butterfly style valve on the intake, I'll see what I can do.
This filter is one of those higher flow ones, its label says 0.31" w.g. resistance. I guess I can go a little heavier on the pre-filters too. The blower should arrive thursday/friday. I'll update then.
|
|
|
Post by lloyd on May 12, 2009 22:22:52 GMT -5
Aren't the fans built to handle a certain inflow resistance and airflow? I would worry that restricting the inflow might overload the fan and increase wear and cause overheating.
|
|
|
Post by doug on May 13, 2009 6:14:32 GMT -5
Lloyd said "Aren't the fans built to handle a certain inflow resistance and airflow? I would worry that restricting the inflow might overload the fan and increase wear and cause overheating. "
It all depends on the design of the system. Some systems depend on this air flow to cool the motor, but other systems do not. In this case you should look and see if the main air flow causes any air to move through the motor windings. If it does then you might have a problem. From what I can see by the photo, it looks like the motor probably has its own fan inside it, and therefore no problem, but I could be wrong.
I also agree that restricting the air flow at the input is the correct way to go if the air is not needed to cool the motor.
Doug P.Eng. (electrical )
|
|
|
Post by hackerberry on May 13, 2009 11:59:17 GMT -5
Wow, good thing we have professionals here in the forum.
hb
|
|