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zeegos
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Wiring a 12V centrifugal fan to mains - help
#24898778 - 01/08/18 03:20 PM (7 years, 9 days ago) |
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Hi folks,
Looking for a little advice on wiring a 12V dc blower to the mains (UK) for my 24x24 soon to be flow hood! 
I've wired a pc fan in my time but this is a bit more substantial!
So it's a single speed fan, at a static pressure of 0 the current input is 26.4A and flow of 537 CFM, at 1.2 inch h2o static (approx total of my HEPA + pre filter) the current is 22.6A and 413 CFM (just over the required 400 CFM). Two wires, black and red.
So from what I've gathered I'll need a 12V ac/dc power supply that's capable of putting out at least 30A, or should it be more?
What would be the recommendation with regards to fuse (or breaker?) rating, and any additional components that may be required?
Also would you recommend a speed controller for this if the (theoretical) air flowrate is only in the region of 20 CFM higher than that required? I guess the intake can be part blocked...
Any advice, pointers would be much appreciated
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MrRabbit-HMR
Professional Duck Washer


Registered: 08/20/17
Posts: 262
Loc: UK
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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24898864 - 01/08/18 03:57 PM (7 years, 9 days ago) |
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Mate, I'd get a sparky to wire it up for you if you don't know how to do it yourself. Bodging electrical shit when you don't fully understand it is a recipe for disaster...
Probably not the response you were after, just be careful and don't blindly believe anything you're told without truly understanding it first...
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zeegos
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Re: Wiring a 12V centrifugal fan to mains - help [Re: MrRabbit-HMR]
#24898941 - 01/08/18 04:34 PM (7 years, 9 days ago) |
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Understand your concern but I have done similar electrical work previously with a 6" ruck fan wired to a variac speed controller, done some pH transmitter wiring in my time and all, with the right information and instruction it's not hard, which is what I'm after
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nolez
Explorer



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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24898983 - 01/08/18 04:57 PM (7 years, 9 days ago) |
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30 amp breaker and #10 thhn or bigger wire. Don't kill yourself.
Eta - that's for the dc side based on info you posted. The ac side may be different. You'll have to check the voltage/amperage requirements of the transformer you get and make sure it's rated for at least 30 amps at whatever voltage. High voltage = less amps and smaller wire/breaker.
Edited by nolez (01/08/18 05:04 PM)
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Gele
Ele



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Re: Wiring a 12V centrifugal fan to mains - help [Re: nolez]
#24899043 - 01/08/18 05:18 PM (7 years, 9 days ago) |
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You can find 12v 30A power supply from PC tower , maybe you will need extra circuit for soft start of the fan. 30 A will activate short circuit protection unless motor has soft start. But still cheapest way to go.
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zeegos
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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24900782 - 01/09/18 01:38 PM (7 years, 8 days ago) |
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Quote:
nolez said: 30 amp breaker and #10 thhn or bigger wire. Don't kill yourself.
Eta - that's for the dc side based on info you posted. The ac side may be different. You'll have to check the voltage/amperage requirements of the transformer you get and make sure it's rated for at least 30 amps at whatever voltage. High voltage = less amps and smaller wire/breaker.
Haha I'll try avoid that outcome 
So I'm looking at one here for only 13 bucks, AC 230V to DC 12V 30A universal regulated switching power supply adapter UK, input voltage 110 - 230V, sounds about right?
Quote:
Gele said: You can find 12v 30A power supply from PC tower , maybe you will need extra circuit for soft start of the fan. 30 A will activate short circuit protection unless motor has soft start. But still cheapest way to go.
Hmm is a soft start incorporated into some motors? Can't seem to find anything on my model of fan apart from voltage, current etc. Just been searching for 12V DC 30A soft start and getting a lot of results for motor speed controllers, would this do the trick?
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Gele
Ele



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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24900804 - 01/09/18 01:50 PM (7 years, 8 days ago) |
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Well different power supply will be different in tolerating shortage current when motor starts(he will start with 50 or more amps). If it shuts off the power supply you can start it with switch 0-1-2 in position 1 in series with 12v 70w light bulb. it will give 5A current (for soft start), an in position 2 direct on power. Note the switch should be rating 30 or more A.
Quote:
zeegos said:
Hmm is a soft start incorporated into some motors? Can't seem to find anything on my model of fan apart from voltage, current etc. Just been searching for 12V DC 30A soft start and getting a lot of results for motor speed controllers, would this do the trick?
Motor in auto is powered with battery, 30A is not much for car battery so no soft start incorporated. As for power supply go for rating more then 30A, so to avoid overload if motor is running for longer period. Speed controller will give nice soft start
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Edited by Gele (01/09/18 02:02 PM)
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zeegos
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Re: Wiring a 12V centrifugal fan to mains - help [Re: Gele]
#24900971 - 01/09/18 02:53 PM (7 years, 8 days ago) |
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Quote:
Gele said: Well different power supply will be different in tolerating shortage current when motor starts(he will start with 50 or more amps). If it shuts off the power supply you can start it with switch 0-1-2 in position 1 in series with 12v 70w light bulb. it will give 5A current (for soft start), an in position 2 direct on power. Note the switch should be rating 30 or more A.
Quote:
zeegos said:
Hmm is a soft start incorporated into some motors? Can't seem to find anything on my model of fan apart from voltage, current etc. Just been searching for 12V DC 30A soft start and getting a lot of results for motor speed controllers, would this do the trick?
Motor in auto is powered with battery, 30A is not much for car battery so no soft start incorporated. As for power supply go for rating more then 30A, so to avoid overload if motor is running for longer period. Speed controller will give nice soft start 
Thanks Gele, interesting method with the lightbulb, see what you mean.... after reading it a few times lol.
So is the idea with a soft start speed controller just to start it on low and slowly ramp up?
With your recommendation of a higher current power supply I've now got my shopping list as 50A supply unit, 30A breaker and 30A soft start speed controller, sound about right? And of course associated cable rated for the duty
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Gele
Ele



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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24903327 - 01/10/18 02:58 PM (7 years, 7 days ago) |
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Sound perfect
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zeegos
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Re: Wiring a 12V centrifugal fan to mains - help [Re: Gele]
#24903381 - 01/10/18 03:27 PM (7 years, 7 days ago) |
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Just a final check before I place my orders for supplies, this is my understanding of how this will work, please correct me if I'm wrong...
230V AC to 12V DC power supply (min 30A), connect up input with cable and plug to draw power from the mains. 3A or 13A fuse for the plug?
Connect +/- 12V DC wires from output of power supply to input terminals of a speed controller with soft start rated to at least 30A, put 30A breaker in the +‘ve line
Connect +/- 12v DC wires from fan to the motor terminals of speed controller
Then flick the mains switch at a distance with a wooden broom handle. Job done? 
Just looking at price comparison between 30A and 50A power supplies, the 50A is almost triple the price of a 30A, would a 30A not suffice if the fan is only drawing a max of 26.4A? Guess I could maybe get something in between...
Edited by zeegos (01/10/18 04:28 PM)
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zeegos
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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24905764 - 01/11/18 03:50 PM (7 years, 6 days ago) |
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Bump 
Power supply ordered, just looking at soft start speed controllers, can't seem to find any suppliers in the UK, I guess China it is. The one I'm looking at supports 12V input / output with max 30A output (360W), control range 0 - 100%.
I've been searching all over for flow hood builds where sort starts are used for the motor and can't find anything, is this definitely the way to go?
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Gele
Ele



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Re: Wiring a 12V centrifugal fan to mains - help [Re: zeegos]
#24908115 - 01/12/18 02:15 PM (7 years, 5 days ago) |
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30 amp powers supply will heat it self and will do the job for short time before blows. You will need soft start only because the used motor (rating 30A)will need more of 30A to start witch power supply will detect as short circuit. And soft start (or DC motor speed control ) will help you to start with less power until motor get it to speed.The flow hood you've been watching use 110 or 220 V AC for powering the fan, witch take less current so no extra part for starting the fan. According to me definitely the way to go.
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zeegos
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Re: Wiring a 12V centrifugal fan to mains - help [Re: Gele]
#24911664 - 01/13/18 06:57 PM (7 years, 4 days ago) |
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I find it odd that a 30A rated supply wont be able to handle continuous 23A output, but then again my knowledge of electronics isn't exactly great!
Yea noticed a few threads where folk are using AC fans, I had a hard time sourcing any fan capable of the required flow rate at a reasonable price, 100 bucks is as cheap as I could get. Bit more work converting to DC in my case but luckily not too expensive
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