Fan power draw?

Five.Stars · 19 Jan 2013 at 18:47

Hi there, I am looking to put my 3 radiator fans on a single channel of my fan controller. The controller has a maximum of 10w per channel.

I am trying to calculate the wattage of the 3 fans and require a little help. Obviously I know to calculate the power it is current multiplied by voltage, but which current do I use?

The fans are Gentle Typhoons (1850rpm) and according to the documentation:

Rated Voltage: 12V
Operational Voltage Range: 5.0~13.2V
Rated Current: 0.083A
Starting Current: 0.360A

I am worried that the starting current for the 3 fans would draw to much power from the single channel. Nearly 13 watts by my calculation. Would this be a correct assumption, and mean 3 on the single 10W channel is not possible?

I can obviously put them on different channels, but wanted the rad fans all on single channel for ease of adjusting etc.

sieze2 · 19 Jan 2013 at 20:49

Five.Stars said:
Hi there, I am looking to put my 3 radiator fans on a single channel of my fan controller. The controller has a maximum of 10w per channel.

I am trying to calculate the wattage of the 3 fans and require a little help. Obviously I know to calculate the power it is current multiplied by voltage, but which current do I use?

The fans are Gentle Typhoons (1850rpm) and according to the documentation:

Rated Voltage: 12V
Operational Voltage Range: 5.0~13.2V
Rated Current: 0.083A
Starting Current: 0.360A

I am worried that the starting current for the 3 fans would draw to much power from the single channel. Nearly 13 watts by my calculation. Would this be a correct assumption, and mean 3 on the single 10W channel is not possible?

I can obviously put them on different channels, but wanted the rad fans all on single channel for ease of adjusting etc.

I bet it would be fine as its only a brief spike. That said its your choice ...

Tattysnuc · 19 Jan 2013 at 22:02

It depends on how your controller handles the 13 watts. If it only provides 10watts then 2 of them will start up, fine, the 3rd kicking in once the current on the other 2 drops.

How are you splitting the cable to power 3 fans off one channel? Make sure that whatever you stick between all 3 fans can take 3x0.36a=1.08amps - I can;t imagine you'd have a problem, but best check...

Tealc · 20 Jan 2013 at 11:15

Startup current will be only momentary. You should be fine.

eddyr · 20 Jan 2013 at 11:56

I would be surprised if the controller couldn't handle the short spike.
You could always lower the voltage of the fans, which will then have a lower peak draw (below 10w) but last for a bit longer.

Kaynar · 20 Jan 2013 at 12:37

Hello,

Motors like the one you mention require higher starting current in order to magnetize (that is part of how they work). There are 3 possible options for you here:
1)The fan controller will manage to momentarily give more than its stated output (we cant know for sure because we dont know how much overdesigned the particular controller is) and everything will be fine.
2) The controller's circuits will wear down considerably faster than normally if you start you pc very often cause it will try to meet the load, but I cant give you an estimation of the wearing for the same reason as 1)
3) The controller will not meet the required load and the fans will not start properly, make some weird noise and maybe finally work normally, but that may wear them very fast.

EDIT: there is actually one thing that I didnt mention. If your controller is at (say) 20-40% fan speed function when you start up ur PC, that means it will be giving less voltage (5-6-7 V ?) so you might actually be fine for that reason?