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Anonymous
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 thermally protected blowers 
#2608244 - 04/27/04 09:34 PM (13 years, 3 months ago) |
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ive found a blower to accomidate a 24x48 filter (well over) the only problem is that it is thermally protected this doesnt seam to be huge problem but the motor tends to run quite hot ive added a heat sink bout it still cuts off after 20 minutes on (from cold) and turns on again every 3 minutes of cooling would this be a huge problem if being used as a flowhood blower or not. if so how could i defeat the thermal protection or cool suffuciently
lil help
thanx in advance
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Anonymous
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 Re: thermally protected blowers [Re: ]
#2614884 - 04/29/04 05:20 AM (13 years, 3 months ago) |
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uhmmm....
lil help 
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 debianlinux
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Re: thermally protected blowers [Re: ]
#2615282 - 04/29/04 10:44 AM (13 years, 3 months ago) |
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don't disable the thermal protection unless you want to have to buy a new motor. the coils in the motor will burn out.
when using a flowhood I cannot imagine how it would be a good thing for the thing to be operating intermittently.
the heat sink is a great idea (my FH motors have heat sinks). your just gonna have to increase the heat sink efficiency. try heat transfer grease, maximize suface contact with the hottest parts of the motor. maybe install a small heat sink fan, reconsider how hard your running the motor... a flowhood doesn't have to whip up a tornado or anything even close, you should just barely feel the breeze, my motors have a rheostat throttle, check for that.
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Anonymous
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Re: thermally protected blowers [Re: debianlinux]
#2615976 - 04/29/04 01:39 PM (13 years, 3 months ago) |
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yeah its controlled on a dimmer so it doesnt rage all the time.when its on low it doesnt cut off for 5-6 hrs
do you think the air from the intake (that ide put on the opposite side of the blowre closer to the motor not the intake) would cool it sufficiently (venturi action)
liquid cooled? bad idea?
thanx for the response
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 Cow Shit Collector
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Re: thermally protected blowers [Re: ]
#2620139 - 04/30/04 07:35 AM (13 years, 3 months ago) |
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Quote:
you said: when its on low it doesnt cut off for 5-6 hrs
Check to see if this speed is laminar. Like Debianlinux said, "a flow hood doesn't have to whip up a tornado or anything even close, you should just barely feel the breeze."
If the fan will create the correct flow and run for 5-6 hours then you should be good. If your running your hepa for 5-6 hour increments, many times, it will also wear out the filter faster.
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RogerRabbit
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Re: thermally protected blowers [Re: ]
#2645045 - 05/06/04 01:06 PM (13 years, 3 months ago) |
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Quote:
mechmono said:
yeah its controlled on a dimmer so it doesnt rage all the time.when its on low it doesnt cut off for 5-6 hrs
That is exactly the problem. You can't use a dimmer on an AC motor. You will burn it out. The speed of an AC motor is determined by the frequency of the current. In the U.S. it's 60hz. If your motor runs too fast, which I doubt, you'll have to get a motor speed controller. They make them for ceiling fans, and they're not much more expensive than a lighting dimmer. You'll need to get one of those, and you'll stop tripping the thermal overload.
I like a flow hood to blow fairly hard. A decent test is to light a bic lighter 12" from the face of the flow hood. It should blow the flame to the horizontal, but not blow it out. If it does this, you have the right flow. If it blows out the flame, either get a motor speed controller, or reduce the intake air. You can put a piece of foil or wood over part of the intake for the same result.
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RogerRabbit
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Re: thermally protected blowers [Re: RogerRabbit]
#2645061 - 05/06/04 01:09 PM (13 years, 3 months ago) |
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Why did my answer in the above post look like part of the quote? What did I do wrong? Only the first sentence above is a quote from mechmono's post. The rest is my response.
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scatmanrav
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Re: thermally protected blowers [Re: RogerRabbit]
#2654858 - 05/08/04 11:02 PM (13 years, 3 months ago) |
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You put your answer before the end quote, edit your post and move it.
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Anonymous
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 Re: thermally protected blowers [Re: scatmanrav]
#2656894 - 05/09/04 03:30 PM (13 years, 3 months ago) |
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rogerrabbit
ill run the blower on full current and test your theroy, i thought it would work
i think a speed controller is required cuz at full blast i can blower a lighter off of my work bench (1/3 hp motor on a blower is real deal)
wish me luck ,if a "speed controller works" youll get a 5 mush rating from me for sure this problem has been plaguing me for a long time
thanx for the insight
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Anonymous
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Re: thermally protected blowers [Re: ]
#2656964 - 05/09/04 03:53 PM (13 years, 3 months ago) |
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the motor only ran for 15 min when it was on @120v 60 hz
are you sayn if i had a speed contoller that it would run at 60 hz and differential voltage instead of a dimmer that makes the 60 die off and inturn make the motor run hot?
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RogerRabbit
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Re: thermally protected blowers [Re: ]
#2718570 - 05/23/04 03:47 PM (13 years, 2 months ago) |
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No,
A speed controller will vary the frequency of the AC current supplied to the motor. An alternative would be to close off part of the intake. This will make the blower move less air, thus reducing the 'work' it is doing, and therefore the current draw and heat produced. Try putting something over the intake and blocking 2/3 of it. If that doesn't help and it still trips the overload, chances are the motor is toast. Sorry to take so long to reply. I only make it over here once or twice a month.
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psilomonkey
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Re: thermally protected blowers [Re: RogerRabbit]
#2727443 - 05/25/04 01:37 PM (13 years, 2 months ago) |
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No, don't close off the intake, this will make the problem worse. The problem is that you are making the fan is working against a static pressure at a speed beyond its rating.
Speed controlers work by pulse width modulation, the don't change the frequency, they just switch the power in and out very fast reducing the overall amount of energy, AC one have to do this in time with the supply current or you get a lot of mains noise generated, which can break stuff.
A speed controller is your answer.
EDIT: Oh, did not see that about the dimmer, the dimmer is a speed controller. Check the dimmer is rated for the motor and the motor is rated high enough to work against the static pressure created by the filters.
Edited by psilomonkey (05/25/04 01:45 PM)
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NewfoundFreedom
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Registered: 05/06/04
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Re: thermally protected blowers [Re: ]
#2727528 - 05/25/04 02:07 PM (13 years, 2 months ago) |
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You could use a heatsink with the same principle as a wort chiller. coiled copper tubing hooked up to a faucet, run water through this and have the water run outside the window or wherever.
Edited by NewfoundFreedom (05/26/04 12:08 PM)
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Anonymous
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water cooled laminar flow hood motor thats taking it to another level im not trying to get to
ill gunna give a go with a speed controller hope one works
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