Seasonic S12 III Power Supply Installation Guide

June 12, 2024
Seasonic

Seasonic LOGO POWER SUPPLY
INSTALLATION GUIDE

S12 III Power Supply

WARNING! IMPORTANT SAFETY INFORMATION

  • NEVER, under any circumstances, open the power supply unit. High voltage inside. WARRANTY IS VOID once the cover is removed.
  • DO NOT insert any object into the fan grill or the ventilation area of the power supply unit.
  • DO NOT place any object in front of the fan or the ventilation area of the power supply unit that may obstruct or restrict airflow.
  • USE ONLY the Seasonic modular cables provided with the power supply unit.
  • Keep the power supply unit in a dry environment, away from humidity.
  • The power supply unit is for integration into a computer system and not intended for external or outdoor usage.

Warning!
This device complies with Part 15 of the FCC Rules.
Operation is subject to the following two conditions:

  1. this device may not cause harmful interference, and
  2. this device must accept any interfer ence received, including interference that may cause undesired operation.

Remove your old PSU (power supply unit)

1.1. Disconnect your AC power cord from the wall socket and the back of the power supply.

Seasonic S12 III Power Supply - PSU 1

1.2. Disconnect all DC cable connectors.
1.3. Remove all 4 mounting screws.

Seasonic S12 III Power Supply - PSU 2

1.4. Remove your old PSU.

Seasonic S12 III Power Supply - PSU 3

Test your Seasonic PSU before installation

2.1. Plug the AC power cord into the PSU.
Make sure that the AC power is coming directly from the wall outlet.
It is recommended to use a high quality surge protector to protect the PSU and the system.

Seasonic S12 III Power Supply - installation 1

2.2. Connect both the 18-pin and 10-pin connectors of the motherboard cable to the PSU.
2.3. If your power supply features a fan control switch, set it to “Normal” Mode*.

  • In Hybrid or Fanless Mode (S³FC) the fan will not turn.

Seasonic S12 III Power Supply - installation 2

2.4. If you have a Power Supply Tester, attach it to the 24-pin motherboard connector. There is a notch on the Tester that helps to make a perfect fit with the 24-pin connector.
If you do not have a power supply tester, refer to the paper clip method described below.

Seasonic S12 III Power Supply - installation 3

2.5. (Optional) For testing a Fanless PSU or a PSU without the fan control switch, attach an external fan or LED light using a Molex cable to the PSU.
2.6. Turn on the power supply by setting the I/O switch to the “I” (ON) position.
If the power supply fan starts spinning (or the externally attached LED light turns on), then your PSU is working.
Paper clip method

Use a paper clip or a piece of wire to create a short circuit on the 24-pin motherboard connector by connecting the pins shown on the illustration.
The drawings illustrate a fully modular PSU with a fan control switch and a Power Supply Tester; the features and accessories of your PSU might be different.

Position your PSU

3.1. Bottom of the case
The fan control setting determines the optimal PSU placement.

Seasonic S12 III Power Supply - Position 1

In “Hybrid” mode
Seasonic recommends to install your PSU with ventilation top cover facing UPWARD, towards the direction of the motherboard. This will ensure natural heat dissipation.
Fanless PSU
The PSU must be mounted into the computer case with the ventilation top cover facing UPWARD.

Seasonic S12 III Power Supply - Position 2

In “Normal” mode
Although the direction of mounting is optional, it is not recommended to install the PSU with the ventilation top cover facing downward if there are no ventilation holes on the bottom of the case. There should always be enough clearance left between the PSU and the bottom case panel.
To learn about the ventilation of your computer case, please refer to the case manufacturer’s instruction manual.
3.2. Flat Desktop-, SFX- or ITX systems

In general, it is recommended to mount the PSU with the ventilation top cover facing the motherboard. Due to the different varieties of case layouts, however, please also consult the case manufacturer’s instruction manual for more information.
3.3. Top of the case

Seasonic S12 III Power Supply - Position 4

Seasonic recommends the PSU to be mounted with its ventilation top cover facing DOWNWARD.
3.3. Top of the case

Seasonic S12 III Power Supply - Position 5

Install your Seasonic PSU

4.1. Secure all 4 mounting screws.
4.2. Make sure the PSU power switch is in the “O” (OFF) position.
4.3. Select the fan control type if your PSU has this option.

Seasonic S12 III Power Supply - Position 6

Note: First power OFF the PSU before changing the fan control to take effect.

Seasonic S12 III Power Supply - Position 7 4.4. Connect all the necessary system DC cables (Motherboard, CPU, VGA, HDD, Optical Drivers, etc). The connectors should click to lock in.
ATTENTION! Use only cables provided by Seasonic! Should you require additional cables, please contact Seasonic.
Motherboard Cable
Please make sure both connectors on the power supply side are properly connected.

Seasonic S12 III Power Supply - Motherboard Cable

CPU and PCIe Cables (8-pin connectors)

Seasonic S12 III Power Supply - PCIe Cable

Peripheral Cables (6-pin connectors)

Seasonic S12 III Power Supply - PCIe Cable 2

ATX 3.0 Compatible 12VHPWR Cable (16-pin connector)

Seasonic S12 III Power Supply - HPWR Cable

Note: The power supply drawings are for illustration purposes only, your actual model might look different.
High powered graphics cards are usually outfitted with two or three PCIe power connector slots. Seasonic prefers the use of two or three separate PCIe cables to connect these cards to your power supply.
Recommendations

Two PCIe power connector slots Three PCIe power connector slots

Seasonic S12 III Power Supply - power connector 1| Seasonic S12 III Power Supply - power connector 2

ATTENTION! The intended use of the PSU is to power PC systems. For mining usage, please contact Seasonic for special cables.

Seasonic S12 III Power Supply - special cables

4.5. Connect the AC power cord to the PSU.
Plug the AC power cord into the wall socket.
4.6. Click the AC ON/OFF switch to the “I” (ON) position.
User Manual

Seasonic S12 III Power Supply - QR Code http://bit.ly/seasonic-digital-manual

Product Registration

Seasonic S12 III Power Supply - QR Code 2 http://bit.ly/seasonic-register

Headquarters
Sea Sonic Electronics Co., Ltd.

Seasonic S12 III Power Supply - QR Code 3 Sea Sonic Electronics Co., Ltd. 8F, #19, Alley 360, Sec.1,
Neihu Road Neihu, Taipei, Taiwan, R.O.C.

American Office
Seasonic Electronics, Inc.
16025 Arrow Hwy Suite A/B,
Irwindale, CA, 91706, USA
European Office
Sea Sonic Europe B.V.
Rietveld 7, NL – 5258 ED
Berlicum, The Netherlands

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