Overload Tests

Before performing our overload tests we always like to test first if the over current protection (OCP) circuit is really active and at what level it is configured.

We configured +12V1 input from our load tester with a low current (1 A) and increased current on +12V2 input (which was connected to the power supply +12V1 rail) until the power supply shut down. This happened when we tried to pull more than 18 A, which is great, meaning that OCP is really active and only 2 A above what is printed on the label (16 A).

The maximum amount of power we could pull from Zalman ZM600-HP with it still working inside ATX specs can be found below. Even at this extreme configuration noise level was still halfway the maximum allowed, peaking 60 mV at +12V2 and 24.4 mV at +5 V.

Input Maximum
+12V1 33 A (396 W)
+12V2 18 A (216 W)
+5V 13 A (65 W)
+3.3 V 13 A (42.9 W)
+5VSB 2.5 A (12.5 W)
-12 V 0.5 A (6 W)
Total 741 W
% Max Load 123.5%
Room Temp. 45.2° C
PSU Temp. 44.3° C
Load Test Pass
Voltage Stability Pass
Ripple and Noise Pass
AC Power (1) 923 W
Efficiency (1) 80.3%
AC Power (2) 952 W
Efficiency (2) 77.1%
AC Voltage 104.2 V
PF 0.999

Under this configuration efficiency dropped below 80% (consider the results marked as "2", as they are the correct ones, measured with our precision power meter).

Above this configuration the power supply would not turn on, showing its protections in action. So you don’t need to be afraid, this unit won’t die or explode if you pull more than it can handle.

Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.


Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.