Fan/Blower recommendation for standard hood?

[MGH]

Hi all,

I’m looking for a recommendation on a fan/blower to use for this fume hood.

I just bought this hood on a GovDeals auction. I had to drive 7 hours each way to pick it up, but with a winning auction price of $41 I couldn’t pass it up.

This is a six foot hood with an operating sash height of 18 inches and effective width of 5.5 feet. In searching so far I understand that I need a fan that will pull at least 825 cfm. Is there a certain model or style of fan that is recommended? I am still trying to put this together on a small budget, so I’m wondering if a squirrel cage fan or restaurant equipment fan would adequate (if I can find one cheap). But of course I don’t want to go to the trouble of installing anything that I’ll have to replace in six months if it’s just going to get eaten up by acid fumes.

I do plan on setting up a scrubber system as well. I’m hoping to get the hood hardware set in place first.

For those eagle-eyed readers out there, yes I do have the panels that snap onto the brackets at the back of the hood .

Thanks for any advice and direction,
Matt H.

 

[niteliteone]

You can try USPlastics they carry some nice blowers that are chemical resistant
here is the link;
http://www.usplastic.com/catalog/search.aspx?search=exhaust%20fan&page=1

 

[Smack]

Those are baffles that go in the back of the hood and should be fastened with nylon rivets from the factory. Are you going to set it up on epoxy resin counter top? Will have to be set up on a 30" standard counter top so plan your base cabinets accordingly. I'm guessing a 6"x20" exhaust hole in the top? And does it have a flange or a transition in place? You can spend 2k on a exhaust blower for that hood easily, not easy to find a used one that will work for how your going to need it set up. The type of exhaust blower will determine to some degree what kind of ducting you'll have to use. Piecing ducting together with odds and ends is a nightmare. Noxx got a nice chemical proof blower from somewhere and he put the link up but like I said, they ain't cheap.
PVC Ducting- http://www.harvelduct.com
Fume Hood Guide- http://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=12641
Best price on counter tops I could find- http://keurindustries.com Just over $600.00 on a 6' epoxy resin top with marine edge.

 

[MGH]

Thanks guys for the great links and advice on the overall setup. I was a little worried about the price of an appropriate blower, and that $2000 price tag confirms it. No regrets though. I still got a good deal on a hood that I can set up... eventually.

To answer a couple of questions:

Are you going to set it up on epoxy resin counter top?

Maybe. I was planning on starting off with building a table out of 2x4s with a plywood top (same as I've done with aquarium stands before) then laying a 1/4 to 1/2 inch thick sheet of polymer on top for the work surface. I'd need to do a little research on acid resistance and hardness. An epoxy resin surface would be great, but if I can go a little cheaper I may try on this point.

And does it have a flange or a transition in place?

Yes, it has a transition already in place. I haven't taken the exact measurements yet, but I think it's more like 4 x 20 inches.

I was hoping to get this all installed before winter really set in. But I've done enough refining so far to know that one of my top five rules is "Don't try to rush things". At least now I have a much better idea of what to look for in searching for used materials. Thanks again for the help. Any other advice is equally welcome.

-Matt H.

 

[niteliteone]

Thanks guys for the great links and advice on the overall setup. I was a little worried about the price of an appropriate blower, and that $2000 price tag confirms it. No regrets though. I still got a good deal on a hood that I can set up... eventually.

To answer a couple of questions:

Are you going to set it up on epoxy resin counter top?

Maybe. I was planning on starting off with building a table out of 2x4s with a plywood top (same as I've done with aquarium stands before) then laying a 1/4 to 1/2 inch thick sheet of polymer on top for the work surface. I'd need to do a little research on acid resistance and hardness. An epoxy resin surface would be great, but if I can go a little cheaper I may try on this point.

And does it have a flange or a transition in place?

Yes, it has a transition already in place. I haven't taken the exact measurements yet, but I think it's more like 4 x 20 inches.

I was hoping to get this all installed before winter really set in. But I've done enough refining so far to know that one of my top five rules is "Don't try to rush things". At least now I have a much better idea of what to look for in searching for used materials. Thanks again for the help. Any other advice is equally welcome.

-Matt H.

Matt,
To get up and running cheaper, you can start out with a metal squirrel cage blower by cleaning it real good and painting the insides with an epoxy paint. This should last a year or two depending on how much you use it, giving time to get the proper blower assembly. I usually pick up used blowers for $25 from a commercial roofer I know, so their cheap used.
I would but the plastic ducting from the start though, since the cost is not much different than the cheaper metal stuff.

 

[jonn]

I may have a blower you'd be interested in. It's resin, came out of a lab connected to a fume hood. Pm me if interested and I will send pictures. Jonn

 

[MGH]

To get up and running cheaper, you can start out with a metal squirrel cage blower by cleaning it real good and painting the insides with an epoxy paint.

I thought about this too - glad to know it wasn't such a crazy idea. I'll definitely keep this in mind.

I may have a blower you'd be interested in. It's resin, came out of a lab connected to a fume hood. Pm me if interested and I will send pictures. Jonn

PM sent

 

[goldsilverpro]

I bought a steel squirrel cage blower from a scrap metal yard for a song and it lasted for 2 or 3 years until it fell apart.

 

[Smack]

And does it have a flange or a transition in place?

Yes, it has a transition already in place. I haven't taken the exact measurements yet, but I think it's more like 4 x 20 inches.

-Matt H.

4x20" is the exhaust size, a transition would be going (transitioning) from the 4x20" to something like a 10" round ducting. Here is a picture of my exhaust blower, it has an aluminum impeller that I had epoxy coated by a Powder Coating Company and then had to have the impeller rebalanced. It moves just under 900 CFM through 8" round ducting before any scrubber or ducting.

 

[4metals]

A lot depends on where you are working. If this is for a business and you are in a building where other people work, gassing everybody out of the building isn't an option. If you're in a backyard shed you can leave for a few hours when a blower fails its a different story. All of the systems I put in are in places where you have to do everything possible to keep the blowers running, proper materials of construction, preventative maintenance and paying constant attention to the "vibes" the equipment puts out. Motors usually put out a distinctive sound when they work, and start wining when a bearing is drying out or the balance is out of whack.
I am sure the cheap and dirty blowers that GSP used sang a different tune as they aged and were slowly consumed by the fumes. If you are going to go with a metal blower and a spray can of epoxy, pay attention to the blower sounds.

 

[niteliteone]

When you hear that first "Tat-Tat-Tat" it is time to shut it down and replace it while it still works somewhat. Don't wait for that "KA-CHUNG" cause then it stops working that instant. :shock:

 

[MGH]

This is coming together a little better now – at least in my head. Thank you, Smack for the correction. Now I think I better understand what you meant by mentioning that the type of blower will determine what kind of ducting will be needed. So I’ll need to transition from my rectangular exhaust to [probably] a round duct which will connect to the blower – and of course the sizing of that duct needs to match the in feed for the blower. Then of course I’ll need a little more ducting to get from the blower to outside.

The hood and blower will be installed in a detached garage behind the house. So I will be able to monitor suspicious blower noises and simply vacate the work area as a last resort if something fails.

Thanks again everyone for the tips, advice, and warnings.

 

[rickbb]

You can make those cheap squirrel cage fans last longer by taking them apart and painting all interior surfaces.

If you start with a new one then you won't have a rust layer to worry with before painting it.

If you go that route, don't close up those little holes you see inside the housing under the fan cage. You may think your sealing it up good to prevent fume leakage, but those are vent holes to draw air across the motor to keep it cool. If those are blocked your motor will over heat and stop. (Don't ask how I know this. )

 

[Palladium]

Everybody's right. I guess its according to what you are doing like 4metals said. I personally use the squirrel cage metal fan and i get about 2 years. It's cheap and it's effective. Now when it comes to a question of personal safety and the business workplace you better buy the best you can. If it fails and someone even claims they can't smell right anymore because of them smelling something when the system shut down, even if it was only 2 mins, then a jack in the box lawyer is going to have a field day with negligence on your part. Welcome to liberalism!

 

[gold4mike]

I used an inexpensive (mostly) plastic blower from Harbor Freight for my hood. It's lasted almost two years so far and is still going strong. I used six inch plastic pipe through the roof of my shed for the exhaust and used clear plexiglass to make a transition box that friction fits to the blower. I put the box together with RTV silicone.

I bought a second identical blower so I could lift off the transition box and replace the blower in less than five minutes. I fully expected to have replaced the blower by now but it's doing better than expected. They offer a 1-year full replacement warranty for $10 and it's tied to the item number of the blower rather than the serial number so you can get it replaced free if it fails within a year.

Here's a link:

http://www.harborfreight.com/catalogsearch/result?q=blower

 

[MGH]

Thanks everyone. You guys have been a great help.

One more question – more of an HVAC topic. In many of the metal squirrel cage fans I’ve come across (including what I see in the Harbor Freight link above), they appear to be set up to pull in ambient air without any direct ducting, and then discharge through some attached duct. To pull air from the hood I would obviously need to attach a duct to the infeed of the blower. Could someone point out how this is typically accomplished? Or do I just need to find a blower that has a flange ready to receive some ducting?

Thanks again,

 

[philddreamer]

Something like this:
http://www.ebay.com/itm/HO-400CFM-Ventilation-6-Inch-Inline-Cooling-Duct-Fan-Exhaust-Air-Blower-Vent-/370927597513?pt=US_Hydroponics&hash=item565d01f7c9

Phil

 

[gold4mike]

I simply stuck a fitting that looks like a toilet flange on the intake side of the blower using more RTV silicone and friction fit a short piece of plastic pipe into it so it can be quickly removed in case I need to swap the blower.

 

[rickbb]

Yes, a plastic toilet bowl floor flange will fit almost perfectly on the inlet side of a standard squirell cage fan. It's what i have on mine, a little RTV sicilone and your good to go.

 

[niteliteone]

Thanks everyone. You guys have been a great help.

One more question – more of an HVAC topic. In many of the metal squirrel cage fans I’ve come across (including what I see in the Harbor Freight link above), they appear to be set up to pull in ambient air without any direct ducting, and then discharge through some attached duct. To pull air from the hood I would obviously need to attach a duct to the infeed of the blower. Could someone point out how this is typically accomplished? Or do I just need to find a blower that has a flange ready to receive some ducting?

Thanks again,

Real easy to make a flange and connect it with a few screws and RTV silicon.
These pictures are of the one I will be installing on my shop next month. The current flange is 16" but I will be cutting it down to 12" to fit the exhaust stack I have.