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Safety -- Make sure you are safe! |
2009-09-19, 11:16am
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Junior Member
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Join Date: Jan 18, 2009
Posts: 9
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9 mo. old ventilation fan quit working
I have a vexing problem that I hope someone can help with, please forgive the length, but I want to fully describe my setup.
I have a heavy duty inline roof mounted ventilation fan, 900 cfm, 10 in. "exterior mounted blower", suitable for commercial kitchen use.
I use a stripped-down second-hand range hood, 36 x 18 in, with smooth aluminum ducting. The hood has a 7 in. opening, and the fan is 10 in, so I used the step-down duct pieces, rather than cut a larger opening in the hood. I have a sorta Bailey Box arrangement. The top back extends to the wall, (another 18 in.) by way of a plexiglass shelf attached to the back of the hood. The side pieces of the "box" only extend to 12 in. (I need lots of arm room or I feel claustrophobic). The hood rides 3 ft. from my benchtop.
I have a large house fan blowing takeup air from behind me, and keep both front and back garage doors open.
The suction from the fan is (was!) VERY stong, to the point of distorting the flame a little bit.
For the first 6 mo., I was using a hothead with MAPP gas. The fan started squealing after about 4 mo. of use, while still on the HH. I don't know if the squealling means that was the fan starting to have trouble. (I've had squeally bathroom fans that have lasted years!)
In July, I started using a MegaMinor with tanked propane and size 15 oxycon. So I've only been using the hotter flame for about 2 months of the fan life.
Last week the fan started really squealling alot and then just seized up. I can manually turn the blade and can see the motor turning inside, but when I turn the fan on, the overheat cutoff switch trips after about 2 seconds of the fan starting to barely turn.
The fan is under warranty, so I called a repairman.
I had to take the hood arrangement down and clean up the bench anyway, to get up to the fan to investigate...so the repairman couldn't really see what I'd been doing to this fan, heatwise, (which is just as well since it would probably invalidate the warranty)!
The fan was very dusty and dirty inside. It gets very dusty on the top of my bench, probably due to all the air circulation drawing in dirt from outside, and optimized to draw up the vent. The repairman recommends using a filter like on a range hood. But I'm worried the filter will decrease the airflow too much to compromise safety.
The heat could be the problem, as it really got worse when I stepped up to oxygen and megaminor. When I put my hand up where the intake opening is, it's quite warm, but not uncomfortably so. The majority of use on the vent fan, I was still on the hothead, which shouldn't be any hotter than a stovetop with all 4 burners going!
I don't know whether I should drill some holes in the ductwork to draw in some cooler air above the "box" to try to keep the exhaust air cooler across the motor. I think I really should try to filter the air as well. Hopefully, the combination of solutions won't effect the airflow too much, I think I have a little bit I can give up.
If the replacement motor burns up, there will no longer be a warranty, and I'll get a squirrel cage then. But if I can get a little more life out of this fan, I will try, but only if I can do it safely.
Any recommendations or ideas would be so greatly appreciated. I'm just getting started with this wonderous adventure, and it's been sooo frustrating to have this setback!
Thanks for sticking with this long message!
Colette
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2009-09-21, 6:59am
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Just at the begining
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Join Date: Jul 13, 2009
Location: Barrie, Ontario
Posts: 131
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if it was rated for commercial kitchen use then it wasn't the heat, but could have been the dirt. I would just do maintenance on the fan every couple of months, clean it out and lubricate it. kitchen fan are self lubricating (food grease), it's amazing how much gets past the filters. Squeaking is not generally a good sound coming from a fan. If you try a filter I would smoke test it to make sure you are not compromising your draw.
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2009-09-21, 9:11am
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old fart
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Join Date: Apr 18, 2006
Location: st paul mn
Posts: 778
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get a can of WD40, use the red tube on it to spray it on the motor bearings. this can be difficult to do. hopefully some of the oil will make it where it needs to be. otherwise you will need to take the fan apart to oil it. the WD40 will also help- to clean it off as well.
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Mark Wilson
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2009-09-21, 11:19am
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Senior Member
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Join Date: May 04, 2007
Location: San Jose, CA
Posts: 1,212
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Quote:
Originally Posted by laserglass
get a can of WD40, use the red tube on it to spray it on the motor bearings. this can be difficult to do. hopefully some of the oil will make it where it needs to be. otherwise you will need to take the fan apart to oil it. the WD40 will also help- to clean it off as well.
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WD-40 is a very good penatrating solvent, and is good at cleaning out any dust and dirt from the bearings. However, it is not an oil. Over time, WD-40 will leave a varnish like material that will cause the bearings to freeze up tight. (don't ask me how I know this)
Please apply a good oil after cleaning the bearings with the WD-40. One that I like is called Tri-Flow. It has Teflon suspended in the oil to provide additional lubrication.
Malcolm
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ARTCO
Artist's Reliable Tool Company
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2009-09-21, 5:46pm
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Junior Member
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Join Date: Jan 18, 2009
Posts: 9
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I tried lubing the motor with sewing machine oil after it seized, thinking the lack of bacon grease going up the flue could be a problem! No such luck, but maybe it was too late.
I have decided to keep the same duct diameter thru the system, so I took the range hood into a machine shop and had the opening cut out to 10 in. I hope that helps. It makes sense that there was stress on the fan from stepping down to 7 in from 10 in.
I think I will vacuum out the fan once a month instead of using a filter.
THe replacement parts have still not arrived, so I'm getting kinda antsy. Hopefully, I'll be back in business soon.
Thank you for all the helpful replies so far. I'll keep posting my progress. I hope this thread can be useful for others designing their studio, in anticipating some of the things that can happen.
Colette
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2009-09-21, 6:32pm
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Junior Member
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Join Date: Jan 23, 2009
Posts: 29
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pretty sure the 7 inch inlet was the problem. it probably just burned out the motor. cutting the opening on the hood to 10 inches will help a lot. if its a commercial kitchen exhaust fan it should work for years and years.
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2009-09-21, 7:46pm
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Junior Member
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Join Date: Jan 18, 2009
Posts: 9
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Glad to know I might be on the right track with the biggest contributing factor by increasing that hood opening to 10 in to match the fan diameter.
I couldn't find anything in the docs that came with the fan about max temp.
I read in another thread that the exhaust air temp can shoot up to 165 deg. with a large outer-ring torch (which is still way down the road for me!). So I'm guessing that the MegaMinor exhaust is around 140-145 degrees? Does that mean in the area at the front of the torch? Does the air temp decrease much travelling thru the ductwork?
My fan is about 8 ft from the range hood opening, mounted on the roof, 11 feet total from torch, but the motor is inline with the exhaust air passing over it. I haven't been up on the roof, but I am curious to know how hot the air is exiting. It's blowing some crazy air up there, I can hear it from the sidewalk in front of my house...whooosh!
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2009-10-12, 9:13am
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Junior Member
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Join Date: Jan 18, 2009
Posts: 9
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Back up and running at last!
The replacement motor for my ventillation fan has been installed, and I rearranged my hood setup so that there is no step down in diameter of the duct. It's 10 in. thru the system now. Also, I redesigned the ductwork run, so that there are no turns, just straight up to the roof, 8 ft.
Also, I built a plexiglass Bailey's Box around the range hood. With the light coming in, I don't feel clustrophobic, and it's nice to be able to see all around, as I had to set my workbench up as an island, when I took out the turn in the ductwork.
THe whooosh from the fan is alittle loud, but the 900 cfm's are taking all that baaaad air away. The air going into the duct feels much cooler than it did before I burned up the first motor. So I think I have the problem solved. I seem to have less distortion in the flame somehow as well. Smoke test shows all smoke going up the duct in 1-2 seconds.
Originally, stepping down from 10 in. to 7 in. in that ductwork was bad ju-ju. It seems to work MUCH better now.
I'll post a studio pic soon.
Thanks everyone for your help. I loooove this forum!
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2009-10-12, 5:22pm
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Senior Member
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Join Date: Nov 21, 2008
Location: Herndon, VA
Posts: 867
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Fantastic! Thanks for coming back to tell us how your improvements went!
Linda
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