Sign in with
Sign up | Sign in
Your question

Figuring out my AMPS for devices connected via molex to PSU

Last response: in Components
November 23, 2011 11:52:39 PM

I'm looking to power 2 MCP655 pumps, 12 PWM LED fans, 1 SSD, 1 HDD, and 1 blu-ray burner connecting directly to the PSU's molex cables.

I'm trying to figure out how many amps that is. I used the watts / 12 method, so 177 watts / 12 = 14.75 amps. I've been advised not to exceed 18-20 amps per molex cable. It's really convenient to throw all of this hardware on a single cable with a couple pwm splitters and molex splitters. I guess I would feel safer putting the storage/optical on a seperate molex cable, but does it really matter? I mean, if something with the psu goes south, I have to assume everything's at risk.

The PSU is the Corsair AX1200, and the 18-20 amps per cable was recommended by ramguy.

Are my calculations accurate or am I way off in the total watts and amps for those devices?
November 24, 2011 3:14:03 PM

Managed to squeeze another molex connection in there so it goes like this:

molex 1: 2 pumps, 6 pwm fans

molex 2: 1 ssd, 1 hdd, 1 blu-ray burner, 6 pwm fans

The only thing left is to figure out lighting, and which to connect it to. Choice would be a matter of convenience now that I've basically split the backside into two zones. Front is molex 2 area, and rear is molex 1 area.

What wattage/amps are required for molex powered ccfl tubes? I'm thinking about a 6-12 inch single tube.

Best solution

a b ) Power supply
November 24, 2011 7:23:12 PM

The cable isn't an issue so much as the connector. If you have all that daisy chained together with 4-pin molex plugs you'll have a big problem. There's too much resistance in the plugs and you can easily discover that by touching the first one in the chain while under load... it will be very hot.

6 fans is the max for one connector, and not chained together but split with a device like this:
I think you are using that aren't you?

I would feel fine about one cable per list, just not one molex :p  You aren't going to draw too much power from the rail, the PSU will protect you there. But you CAN draw too much power through a single molex connection.

Scroll down and look at the right hand box on this page:

The max draw through that type of connection is 11A.
Related resources
November 24, 2011 7:39:41 PM

I'm sorry. Yeah I didn't mean a single molex connection, but single as in a single cable with 4 molex connectors.

The fans are broken into 4 groups of 3 with akasa splitters.

2x 3-fan splitters on one molex connector, and the 2 pumps on another molex connector.

SSD, HDD, blu-ray burner on a custom 3 SATA to molex connector on one molex connector, of 4, on this separate cable.
Then another 2 groups of 3 fans on the akasa splitters to another molex connector on that line.
a b ) Power supply
November 24, 2011 7:42:21 PM

Yes, I agree the PSU should have no problem running this.
November 24, 2011 7:45:42 PM

I've seen some shots where people try to treat their molex like they do their christmas tree lights and have this huge bar of 6 plus molex chained together... hehe...

I have enough sense to not do that ;) 
a b ) Power supply
November 24, 2011 8:15:05 PM

I figured you meant cable :)  It was more for others benefits that might read this.

November 24, 2011 8:57:38 PM

I know but I'm chatty. Was I still close on my figuring of total amps?
a b ) Power supply
November 25, 2011 1:20:42 AM

Well, it's hard to say really. I think you split them pretty well. Neither will get anywhere near 18A. 2-3 amps for each pump, no more than 1A per fan.
December 1, 2011 11:30:15 PM

Best answer selected by clonazepam.
December 2, 2011 12:29:44 AM

I agree with this...