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shobimono
Why?
Registered: 09/14/04
Posts: 561
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Yet another blower question
#6605202 - 02/24/07 10:33 AM (17 years, 2 months ago) |
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After searching through many posts about blowers for a flow hood I think I'm more confused than when I started.
I got my HEPA, it's 24"x24"x6" 99.99%.
I saw mention by Nan that they used the Dayton blower model #7F735, which has an S Pole motor. He said that he used a rheostat to control the motor speed, but he also said that if you use a rheostat, the motor must of a split capacitor type.
Is S Pole a split capacitor type? Dayton has S Pole and PSC (permanent split capacitor) motors, so I'm wondering why he said he got one type wih a speed control, but mentions that the speed control must be of a different (is it?) type?
The dayton blowers list they have 4 speeds, are these hardwired speeds? like you pick one and you are stuck with it unless you rewire the motor?
It is very dusty here so I want to pre-filter the heck out of the flow hood. I'm thinking that with a couple pre-filters and the 2ftx2ft size of the hepa it would be better to get a strong blower/motor and be able to control the speed via a dial. Can I get either type (S Pole or PSC) to do this?
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mattymonkey
Feel Like aStranger...


Registered: 11/07/04
Posts: 973
Last seen: 11 years, 4 months
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Re: Yet another blower question [Re: shobimono]
#6605212 - 02/24/07 10:38 AM (17 years, 2 months ago) |
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Where are you looking at blowers? Are you thinking of buying a new one?
I ask because I buy them from this guy on ebay "samgreat". He refurbishes them and sets em up nice, usually less then $100 will get you a very powerful blower.
Do an advanced search on his name in ebay. Right now it seems like he just has one, 1800cfm fan, and he's asking a lot for it for some reason. But his prices are usually really good.
For a 24x24" hepa I think you could get away with 800cfm fan, but most that I see are usually in the 1000-1200 range. A little more isn't going to harm things too much, you'll be surprised at how much that HEPA will slow down the airflow. A fan speed control may be kind of expensive for a large fan like this. This seller has sometimes sold ones with a Hi/Low switch, may be all you need.
Check him out and be patient, if you can.  Hope this helped.
-------------------- "listening for the secret.. searching for the sound.."
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RogerRabbit
Bans for Pleasure


Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 1 year, 2 months
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Re: Yet another blower question [Re: shobimono]
#6605230 - 02/24/07 10:44 AM (17 years, 2 months ago) |
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You can't safely use a rheostat to control an AC motor, regardless of type. Speed of AC motors is determined by the frequency of the supply voltage, which in the US is 60hz, and in Europe is 50hz. That's why motors usually have two speed ratings listed, depending on whether they're wired to 50 or 60 hertz. An inexpensive choice is the motor speed controller on this page. http://www.littlegreenhouse.com/accessory/controls2.shtml
Motors that are listed with multiple speeds have individual wires for each speed. Usually, they have a 'common' and then individual wires that you connect to the other side of your supply line depending on the speed you want. You could get a rotary switch to switch between the speeds, or you could use the above motor speed controller and connect it to the highest speed. An alternative to both is to experiment with the various speeds by hand until you find the one that works, and simply leave it connected to that one. You can always block off part of the inake supply to reduce the airflow if necessary. This can be as simple as putting foil or saran wrap over part of your intake filter.
I'd just get a motor that will supply 600 to 1000 CFM @ 1" of static pressure, and adjust down from there. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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shobimono
Why?
Registered: 09/14/04
Posts: 561
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Re: Yet another blower question [Re: RogerRabbit]
#6605277 - 02/24/07 11:07 AM (17 years, 2 months ago) |
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Quote:
RogerRabbit said: You can't safely use a rheostat to control an AC motor, regardless of type. Speed of AC motors is determined by the frequency of the supply voltage, which in the US is 60hz, and in Europe is 50hz. That's why motors usually have two speed ratings listed, depending on whether they're wired to 50 or 60 hertz. An inexpensive choice is the motor speed controller on this page. http://www.littlegreenhouse.com/accessory/controls2.shtml
Motors that are listed with multiple speeds have individual wires for each speed. Usually, they have a 'common' and then individual wires that you connect to the other side of your supply line depending on the speed you want. You could get a rotary switch to switch between the speeds, or you could use the above motor speed controller and connect it to the highest speed. An alternative to both is to experiment with the various speeds by hand until you find the one that works, and simply leave it connected to that one. You can always block off part of the inake supply to reduce the airflow if necessary. This can be as simple as putting foil or saran wrap over part of your intake filter.
I'd just get a motor that will supply 600 to 1000 CFM @ 1" of static pressure, and adjust down from there. RR
Thanks!
I know you had posted about the rheostat/motor speed controller thing before but I couldn't find it. (funny cuz I had that link in my bookmarks from the last time you posted it)
I think I'm leaning toward going well above in CFMs and using lots of prefilters and getting one of those fan speed controls.
Do I need to go with the 10 Amp? or will the basic 5 Amp model work?
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RogerRabbit
Bans for Pleasure


Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 1 year, 2 months
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Re: Yet another blower question [Re: shobimono]
#6605713 - 02/24/07 01:55 PM (17 years, 2 months ago) |
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It will depend on the horsepower of the motor you purchase. The data plate will tell you the full load amps. I doubt seriously that anything you get for a flowhood would pull over 5 amps though.
I don't see any point in stacking pre-filters. Think of it this way: If a chain link fence won't stop a mosquito from flying through it, would two or three chain link fences stacked stop him?
I use the super-allergen furnace filters as a prefilter. I'm still on my original 6 year old HEPA, but change the prefilters twice a year, or whenever the flow starts to suffer.
Make sure when you're done that a cig lighter or candle held in front of it bends between 45 and 90 degrees, but doesn't blow out. Too much flow when doing sterile work is counter-productive. I've actually slowed down my flow hood so the lighter flame only bends 45 degrees, and it seems to work better. The reason is that at 99.99% efficiency, if the contaminant spore load is high, that .001% that gets through is a LOT of trich spores getting through to your work. If you cut the flow in half, only half as many get through. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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agar
old hand


Registered: 11/21/04
Posts: 9,056
Loc: Somewhere Else
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Re: Yet another blower question [Re: RogerRabbit]
#6606351 - 02/24/07 05:57 PM (17 years, 2 months ago) |
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Quote:
I'd just get a motor that will supply 600 to 1000 CFM @ 1" of static pressure, and adjust down from there. RR
Good advise.

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shobimono
Why?
Registered: 09/14/04
Posts: 561
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Re: Yet another blower question [Re: shobimono]
#6608035 - 02/25/07 08:51 AM (17 years, 2 months ago) |
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Here's the link I was looking for where you mentioned the motor speed control
http://www.shroomery.org/forums/showflat.php/Number/4165789
Which leads me to my next question about the plenum.
You mentioned in that thread that you should have a minimun plenum depth of at least the same size as your filter (mine is 24"x24"x6").
Until I found that thread I was thinking that I needed a 2 foot deep plenum. 6 inches seems a little small, so I'm thinking of making it 1 foot deep. I'm wondering if there is a point of diminishing returns if you go too large? ie is 1 foot too large? or should I go larger if I'm getting a "big" blower?
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RogerRabbit
Bans for Pleasure


Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 1 year, 2 months
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Re: Yet another blower question [Re: shobimono]
#6608049 - 02/25/07 09:02 AM (17 years, 2 months ago) |
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I really can't see where that would make a difference going larger. You want to make sure the air is pressurized equally at all points behind the filter, so the air is flowing equally from all points on the clean side of the filter, thus giving laminar flow. It certainly wouldn't hurt to go with 12" behind the filter if you have the space available. My work area is so small, that extra six inches would gobble it up. That's why I still use my tiny 12 X 24, which means I have to get quite creative filling the large, gusseted spawn bags. I'm jealous of you guys with the 24 X 24 and larger hoods. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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shobimono
Why?
Registered: 09/14/04
Posts: 561
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Re: Yet another blower question [Re: RogerRabbit]
#6608065 - 02/25/07 09:09 AM (17 years, 2 months ago) |
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Actually smaller would be better, this thing is gonna be large enough as it is, that's why I was worried about having a 2 foot plenum haha.
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petridish
gutted mycophile
Registered: 02/23/07
Posts: 47
Last seen: 12 years, 9 days
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Re: Yet another blower question [Re: shobimono]
#6616085 - 02/27/07 09:46 AM (17 years, 2 months ago) |
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I can't adjust my plenum as my filter is in it's own prefab case, but I can vouch for the 5amp fan speed control. I can't tell you any thing much about the fan (no data plate) but it's about 16" around at the round portion of the blower case and it has wires for 5 speeds. It's the largest home furnace blower I have encountered, and after prefilter, it has enough juice to almost blow out the lighter when cranked. That's in front of a 2'x4'x6" hepafilter. The speed control works great! I wouldn't worry about the 10 amp model for your hood-to-be. Good luck.
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