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 orchidfanatic
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Registered: 08/12/07
Posts: 832
Loc: where the wild things are
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glad you got it dialed in .. I am working on getting a fan controller to slow my motor down a bit .. I hope a 10 amps controller is enough the
motor is sealed in the case and I didnt write the amperes down before I built the flow hood..
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 ZeropointMind
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Registered: 08/28/05
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Thank you! All the advice everyone gave really helped. It saved me from having someone come here and charge me an arm and a leg to even have a look. Good luck with that amp controller. I found a table in my garage to use under the hood, I've gotta go clean it up, and make sure it is tall enough to have the hood properly enclosed. Slowly things are getting to where they should be. Keep us posted on your outcome with that controller.
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RogerRabbit
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If you know the voltage it runs on, such as 120 or 240 volts, and remember the horsepower, you can calculate the current. There's roughly 746 watts per HP, assuming perfect efficiency. Therefore HP = (Volts X Amps) / 746. Simply switch the formula around to get current. Current = (HP X 746) / volts.
No motor will have perfect efficiency, or a power factor of 1, of course, but that formula will get you ballpark close to the draw on your circuit.
RR
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www.mushroomvideos.com
Ignorance is contagious. Boycott Walmart and watch your IQ go up.
RR
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orchidfanatic
retiree
Registered: 08/12/07
Posts: 832
Loc: where the wild things are
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 Re: Laminar Flow Hood (w/ pic) [Re: RogerRabbit]
#7866748 - 01/11/08 08:44 PM (11 months, 22 days ago) |
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I wish I could remember all those mathematical equations from
the classes I took .. I passed with flying colors but the info just doesnt stick .. use it or lose it .. seems to be the rule ..
thanks for the info RR
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fastfred
Registered: 05/17/04
Posts: 4,417
Loc: Dark side of the moon
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Be careful with those speed controllers. AC motors are only designed to run at certain speeds. Depending on which speed wire you use that energizes certain windings in the motor.
If you were put a simple dimmer switch on your motor you would burn out the switch if you're lucky or the motor if you're unlucky. Dimmer switches don't really adjust the voltage they just clip the waveform of the AC. So you end up with the motor only running at certain settings on the dimmer switch and the phase doesn't match what the motor needs.
A rheostat type speed controller is a lot better, but motors are still designed to run at only one speed. At slower speeds the AC phase angle through the coils at any given moment is not the optimal one.
So anytime you run your motor at less than the designed speed it's going to draw more current and/or generate more heat.
So I don't recommend starting your motor at anything less than the designed voltage. It's also best to use the least amount of slowdown that you can. So start them at full power and adjust them downward just until you get an acceptable airflow.
I'm dealing with the same problem myself at the moment, so I've been reading up on speed controllers and whatnot. The blower I'm working with is way too powerful for the application. To fix that I'm blocking off one side of the intake, allowing a little bit of air to be diverted away at the interface, using a good prefilter, and then using a speed controller to slow it down the rest of the way. That should allow the motor to run pretty close to it's designed speed which should cause the least current increase and minimize extra heat generation.
Thanks to RR for the intake blocking idea.
-FF
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RogerRabbit
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Re: Laminar Flow Hood (w/ pic) [Re: fastfred]
#7868527 - 01/12/08 09:52 AM (11 months, 21 days ago) |
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Hopefully, he's not even THINKING about using a lighting dimmer. Such would cause a fire or other problems very soon. There's been several deaths caused by house fires where idiots used a dimmer switch to control ceiling fans.
Rheostats are simply variable resistors and will control a DC motor, where speed is determined by the current draw. AC motors are controlled by the frequency of the incoming source, so a rheostat wouldn't work.
Motor speed controllers are designed for controlling AC motor speeds. Starting motors at reduced speed is standard operating procedure in industry. I've hooked up hundreds of them, as well as VFDs to control the speed of AC motors. This is my career field. Inexpensive controllers can be found here. http://www.littlegreenhouse.com/accessory/controls2.shtml
RR
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www.mushroomvideos.com
Ignorance is contagious. Boycott Walmart and watch your IQ go up.
RR
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orchidfanatic
retiree
Registered: 08/12/07
Posts: 832
Loc: where the wild things are
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Re: Laminar Flow Hood (w/ pic) [Re: RogerRabbit]
#7868616 - 01/12/08 10:34 AM (11 months, 21 days ago) |
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LOL no its not a dimmer switch its a greenhouse fan controller like RR posted the link to .. its the same place actually I ordered it from them
the prewired 10 amp model..
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fastfred
Registered: 05/17/04
Posts: 4,417
Loc: Dark side of the moon
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Thanks for the info RR. The last couple motor speed controllers I've looked at seem to be simple rheostats.
Could you go into the differences in rheostats, TRIAC type dimmer switches, and how modern variable frequency speed controllers work?
I've heard a lot of different info with respect to using dimmers, rheostats, and variacs to control motor speed.
I worked in the protection relay industry for a time and our models always assumed starting at full power. With a variable frequency device it would make sense to start at a lower speed. With a variac you'd be much more likely to burn something up starting at a slower speed.
I also noticed on your link that the controllers say that they are only for controlling variable speed motors. What exactly do they mean by that? Are they unsuitable for controlling fixed speed AC motors?
The speed control I have looks like a rheostat, but it was billed as a blower speed control. Of course I got it used from someone who insists it's a blower control, so I don't have any real info on it. Is there any easy way to check that without just hooking it up and seeing if it burns out or doesn't control the speed properly. I have all manner of electrical testing equipment short of a scope.
I imagine that VFDs are expensive because they need to rectify and reinvert the power, but maybe I'll have to invest in one.
-FF
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fastfred
Registered: 05/17/04
Posts: 4,417
Loc: Dark side of the moon
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Re: Laminar Flow Hood (w/ pic) [Re: fastfred]
#7869059 - 01/12/08 01:15 PM (11 months, 21 days ago) |
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There are so many types of motors and speed controllers I have to admit that I'm a bit confused.
There are 'universal' AC/DC, permanent split capacitor, induction, shaded pole, soft/slow start, and brushless type motors. How can you tell exactly what kind you have?
Mine is obviously designed for HVAC type use and is brushless. It has a GE motor with three different speed wires. There is really no information on the motor itself, but I measured it to draw 7.2-8.5 amps.
It looks like this...
Any advice on what I can get away with as far as a speed controller or even what type of motor it really is would be appreciated.
-FF
Edited by fastfred (01/12/08 01:21 PM)
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ZeropointMind
Stranger
Registered: 08/28/05
Posts: 67
Last seen: 9 months, 21 days
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Re: Laminar Flow Hood (w/ pic) [Re: RogerRabbit]
#7874337 - 01/13/08 05:00 PM (11 months, 20 days ago) |
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I had the motors up and running the first time for about 30mins then shut them off and went to bed, mission accomplished I thought. Then the next day, I ran the system as you suggested, started them low, and adjusted them to a higher speed via the speed controllers, everything was running well for over an hr, I left the room and came back a few times, all was good. Then the last time I left the room and came back, the right blower was off, and there was that burning smell again. I shut everything off, only the left blower was still going. I looked at the switch connecters (those yellow female ends) and the one connected to the red wire looked even worse. I waited awhile and turned them on again, to hear a small popping noise coming from the switch connecter, then it went away. Thankfully, the motors are still running, so they are not burned out. So either A) I need to change those connecters because of the lack in continuity due to the burned ends and corrosion on the tips and so forth? B) Don't have the speed set so high, as fastfred suggested, or C) All of the above?
The first time where I thought everything was golden, I only ran the system for about 30 mins, and went to bed, the speed was not set as high. On this last occasion, I increased the speed slightly higher, only to find this situation still having the same problem.
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makaveli8x8
Stranger
Registered: 02/28/06
Posts: 7,033
Last seen: 22 hours, 49 minutes
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i finally got mine flowhood up and running, works really well except one thing. After 1.5 hours the room gets warm, and air its blowing feels warm. Their might even be a smell....purhaps you have the same problem as me? I think my blower is weak and overheating
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  We were sent to hell for eternity  Ø h®
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Over-population the root of all Evil-brings the Elites Closer to the gates.
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ZeropointMind
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Re: Laminar Flow Hood (w/ pic) [Re: makaveli8x8]
#7875028 - 01/13/08 07:19 PM (11 months, 20 days ago) |
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Do you have anything to adjust the speed? Or is it wired directly to the plug? Hopefully we can figure out what's goin on... I'm taking everyones advice into account... good luck to you too.
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makaveli8x8
Stranger
Registered: 02/28/06
Posts: 7,033
Last seen: 22 hours, 49 minutes
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its got what looks like a wall switch for a room light (like you see in walls of your house), other than that its wired to a plug
its also a "retired" hvac unit and looks exactly like the picture
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We were sent to hell for eternity Øh®
We play on earth to pass the time
Over-population the root of all Evil-brings the Elites Closer to the gates.
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fastfred
Registered: 05/17/04
Posts: 4,417
Loc: Dark side of the moon
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Re: Laminar Flow Hood (w/ pic) [Re: makaveli8x8]
#7875196 - 01/13/08 07:43 PM (11 months, 20 days ago) |
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What speed wire do you have hooked up? The red one should be the slowest speed wire.
You might try checking how many amps it's drawing if you have a meter. Mine draws 7-8.5A. Careful that your meter will handle at least 10A, hopefully 20A.
Check each speed wire to find if some are drawing way more than any others. One of your windings could be damaged, so another speed wire might work instead of the one you're using.
Other than that I can't tell you much. Mine seems to work fine although I haven't run it for more than a few minutes. I have mine hooked up to a standard type wall switch. Most are rated for 10A or better so that shouldn't be the problem. If they are heating up much or burning out then your blower must be drawing more than 10A, so perhaps there's something wrong with it.
-FF
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makaveli8x8
Stranger
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Re: Laminar Flow Hood (w/ pic) [Re: fastfred]
#7875430 - 01/13/08 08:13 PM (11 months, 20 days ago) |
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well im wondering if my blower was 2 small in the first place, but as for your suggestion, i got it all siliconed up so looking at it is out of the question for me. it was prewired when I got it and sopposedly came out of hvac, so im sure a certified person rigged it up, plus the guy deals with lots of them
I'll check into a meter thow, that sounds like a good easy test
--------------------
We were sent to hell for eternity Øh®
We play on earth to pass the time
Over-population the root of all Evil-brings the Elites Closer to the gates.
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ZeropointMind
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Re: Laminar Flow Hood (w/ pic) [Re: fastfred]
#7875568 - 01/13/08 08:35 PM (11 months, 20 days ago) |
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By increasing the speed adjustment to a higher setting, more amps are drawn in, and lowering it, less amps? If that's the case, I need one of those meters so I know the max I should turn those knobs too, in order to fix this problem. What's the name of that meter by the way? Will it also test RPM?
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RogerRabbit
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Registered: 03/26/03
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Quote:
So either A) I need to change those connecters because of the lack in continuity due to the burned ends and corrosion on the tips and so forth?
Yes. I assumed earlier that you'd change that burned wiring. Never stick a burned spade lug onto a new terminal. That's the problem.
As for a flow hood making the room warmer, that is normal. It's related to the plenum behind the filter. A good HEPA will have enough resistance that static pressure is created behind it. This pressure is compressed air, and compressing air causes heat to be released. I always let my flowhood run for an hour or two at least, in a closed room before working, and it always raises the temperature by ten degrees or more. In addition to the compression related heat, the motor itself will get warm, also increasing room temperature.
RR
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www.mushroomvideos.com
Ignorance is contagious. Boycott Walmart and watch your IQ go up.
RR
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ZeropointMind
Stranger
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Last seen: 9 months, 21 days
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Re: Laminar Flow Hood (w/ pic) [Re: RogerRabbit]
#7876369 - 01/13/08 11:18 PM (11 months, 20 days ago) |
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RogerRabbit
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You'll want to use either 14 or 12 AWG wire. 14 is probably what's there. The two links both point to the same connector. That one will work.
To measure amps, you'll want a clamp on ammeter. You can get them for $20 at lowes or any electrical supply place. You don't need to measure RPM. Adjust your controller so when you light a bic cigarette lighter in front of the flowhood, it bends the flame 45 to 90 degrees, but doesn't blow it out. Less air is generally better than more air when doing sterile work, so shoot for closer to where the flame bends 45 degrees.
RR
--------------------
www.mushroomvideos.com
Ignorance is contagious. Boycott Walmart and watch your IQ go up.
RR
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ZeropointMind
Stranger
Registered: 08/28/05
Posts: 67
Last seen: 9 months, 21 days
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Re: Laminar Flow Hood (w/ pic) [Re: RogerRabbit]
#7876879 - 01/14/08 01:41 AM (11 months, 19 days ago) |
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Would this be ammeter be ok? :
http://www.grainger.com/Grainger/items/1RH89
With this I'll hope to see what amps are pumping into those blowers and adjust accordingly, and not to go over 5amps per motor. Do I measure the amp reading, where my speed adjustment knobs are for each motor? Would you mind describing that, please. Thank you.
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