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AssuredElectrical, Master Electrician
Category: Electrical
Satisfied Customers: 4241
Experience:  Contractor-42+ Years in the ElectricalTrade
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I am looking for help with setting up a few large arrays of

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I am looking for help with setting up a few large arrays of 120mm fans.

1st: 4 banks of 7 fans, 28 total.

These120mm fans are each rated: 12VDC (7.0v to 13.8v range), 0.14amp, 1.68watt.

That should total 3.92amps and 47.04watts. If I am not mistaken and please correct me if I am wrong, I should be able to power all of these fans with an off the shelf 12v 480w computer power supply with a little modification to the power supply (to make it turn on without a mother board) and some extensive wiring. Is there any way to control the speed of all 28 fans? Maybe a rheostat or potentiometer (preferably not a huge one)?

2nd - This one is a bit more complicated. 4 banks of 5 fans, 20 total.

These 120mm fans are each rated: 48VDC (24v to 55.2v range), 0.39amp, 18.7watts

If at all possible I would also like to control the speed of these fans like stated above but in two banks of 10. If it is possable then each bank should total 3.9amps and 187watts. If not together all 20 fans would be 7.8amps and 374 watts.

I have 2 Gennssi 48V DC 7.3A 350 power supplies on the way

Are these the correct power supplies for the setup I am trying to accomplish?

I also have never wired a power supply like these before or much of anything for that matter just some basic wall switches, wall outlets, ceiling fans, A/V equipment and custom computer builds in the past. Would I be able to wire a 3 prong male power socket (like on the back of a computer power supply but with a switch) to each supply and use standard power cables to power the supplies?

Maybe like this:
Amico AC 250V 10A 3 Terminals Rocker Switch C14 Inlet Male Power Plug

Are there any tips or suggestions for a project like this that you could share?

Thank you in advance for any help you can provide,

Jeremy Peck
Welcome. My name is XXXXX XXXXX would be glad to assist.

Hi Jeremy,

I have read over the information and believe I can put together a setup with what you are proposing.

Have built many control cabinets with power supplies, controllers and the like with the same type cooling fans, so have some experience in that area.

Is time an issue though?

It would be sometime tomorrow to get it all together and post. If it is a problem, I can put the question back on the board for others right away.

If it is ok with you, then I can post tomorrow with my information and then you can look it over and see what you think.

Just let me know if this will fit your schedule.
Customer: replied 2 years ago.

Hello Tommy,


Sorry for not responding yesterday. My time table for this project is short but if you could respond today that would be great. I will be assembling most of this project on Monday and Tuesday and it needs to be done before Friday. I would like to leave some time to trouble shoot any hiccups as well.


Did I provide you with enough details of the setup in my question?


Thanks for the help,


Jeremy Peck


Hi Jeremy,
The plan is sound and all the components are certainly adequate .

The only issue I see as a possible trouble spot will be variable speed on the fans.

Using a fan controller allows better control and flexibility as well as keeping heat down and wattage per section of fans.
This is better suited than purchasing variable speed fans or using large rheostat to control speeds because of sizing-costs-heat dissipation.

CLICK HERE for 8 channel on the 12 volt fans

I am unable to find a multi-channel controller for the 48 volt fans as yet, but am sure
someone has them. Few phone calls may find them.
It would certainly be much better than trying to control with a rheostat or single

Let me know your thoughts.

Customer: replied 2 years ago.
Hello Tommy,

Thank you for the assistance, the diagram and for confirmation that the components I have will work for this project.

As for the fan controller, thank you for pointing me to a source. I was hoping to build a fan controller of my own. 1 controller for all 28 12v fans and 1 controller for each bank of 10 48v fans, 3 controllers in total (x1 - 12v 47.04 watts, x2 - 49v, 187 watts). Would that be possible? How?

There is a surplus supply house called Skycraft local here in Orlando that I should be able to get most electrical components that I might need. I just don't know what components I would need or where to start. When I asked some of the personnel at Skycraft they said I would need a very large rheostat or potentiometer. What they showed me was way to big for this project.

Also, what gauge wire should I use for the AC power supply hook ups? I have no experience wiring anything for the AC side of this project. I have added to the bottom of the diagram what I think is the correct setup for wiring each of the 48v power supplies (the 12v supply is an off the self computer power supply and should be easy).

Could you please review the diagram I have attached. I made a few small changes to show exactly the setup I am trying to build.

Thanks again,

Jeremy Peck

P.S. I am having trouble attaching the diagram. Here is a link to the jpeg in my google drive. Please let me know if you are having problems viewing it and thanks agian.

First, #14 gauge is fine for the AC side of the power supplies, it handles 15 amp circuits which is well within the needs here.

I posted the fan controller because when using a large rheostat for the wattage, there is a lot of heat and it adds to the expense. Where the pre-builts save money and they have been designed for the purpose.
They have the built in circuitry and already been through the engineering and design

The one posted is 30 watts per channel, so it could operate all the 12 volt fans itself.

They have others at less wattage per channel that would work-LIKE THIS ONE

Personally, I have never even thought about building my own, prefer to use their engineering to operate fans
at variable speeds instead of building something and then come up short or have to make changes.

200 watt rheostats are a couple hundred bucks and bulky with lost of heat generated.

We always use/d pre manufactured controllers.

I think you would need some engineering to build your own, out of my realm of expertise
on one that would be safe and operable.
Customer: replied 2 years ago.



Thanks again, you have been a tremendous help.


The fan controller is a want and not a need for this project. I did find some guides online for making a rheobus with a potentiometer and some resistors to control a voltage regulator.


Would you know anything about how to setup up somthing like that?


If not, no big deal you've aready been a huge help.


Thanks again,

Jeremy Peck

To be honest, I am not familiar with that type of setup. I know that the proper resistance is needed to keep from burning out the fans and rheostat etc.

That is why I like the prebuilt units, they have accounted for everything with the total wattage output.

If you get one premade unit and look at it, you can see the components they use and understand a little more. There isnt much in them, but it was designed by some good engineering and knowledge

I am sure there are simpler ways, just never got into it on the chance I might burn up a few components or motors.
AssuredElectrical, Master Electrician
Category: Electrical
Satisfied Customers: 4241
Experience: Contractor-42+ Years in the ElectricalTrade
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