What Can Damage A Power Supply?
The number one killer of power supplies is damage due to overheating and/or being overdrawn. Usually this can happen if the cooling device / cooling fan attached to the power supply fails and the operating temperature inside the unit becomes too hot. Another reason could also be improper air circulation throughout your case or dust that collects over time.
Alternatively, by connecting too many components and exceeding the maximum deliverable power capabilities of the unit, you can cause damage as well. It is important to calculate the maximum device drain of your components and ensure that your PSU can deliver that to them. Usually it is also recommended to have some room to spare as fluctuations and future growth can change your numbers.
The formula for power calculation is:
Power = Current x Voltage
Watts = Amps x Volts
Don’t be fooled into using this formula to calculate the total output power of a power supply (based on the maximum ratings on each rail). Rail outputs can be thought of as a ‘Give-and-Take’ system. This means that if you are operating at maximum on the +12V rail, don’t expect to be able to operate at maximum on the +3.3V rail. The more current outputted at +12V, the less you will be able to output at +3.3V, and so on. When manufacturers specify a Maximum Power rating for each rail on the power supply they are oftentimes submitting maximums reached independent of this interaction. These values are also achieved in lab environments so you will rarely see them in practice. In most cases it is recommended to budget a 30% buffer between your system needs and the max rating of the supply.