OCZ Z Series 850 W Power Supply Review
Load Tests
Contents
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test both inputs were connected to the power supply single rail (+12VB input was connected to the power supply EPS12V connector and all other cables were connected to the load tester +12VA input).
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 6 A (72 W) | 13 A (156 W) | 20 A (240 W) | 25 A (300 W) | 31 A (372 W) |
| +12VB | 6 A (72 W) | 13 A (156 W) | 17 A (204 W) | 25 A (300 W) | 31 A (372 W) |
| +5V | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) | 10 A (50 W) |
| +3.3 V | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (30 W) | 8 A (26.4 W) | 10 A (33 W) |
| +5VSB | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 W) | 3 A (15 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
| Total | 174.5 W | 350.2 W | 511.4 W | 683.5 W | 842.1 W |
| % Max Load | 20.5% | 41.2% | 60.2% | 80.4% | 99.1% |
| Room Temp. | 45.0° C | 44.6° C | 45.6° C | 48.3° C | 46.9° C |
| PSU Temp. | 45.1° C | 46.2° C | 47.3° C | 49.5° C | 52.0° C |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 198.9 W | 390.7 W | 573.2 W | 776.0 W | 971.0 W |
| Efficiency | 87.7% | 89.6% | 89.2% | 88.1% | 86.7% |
| AC Voltage | 115.3 V | 114.3 V | 112.9 V | 110.7 V | 108.4 V |
| Power Factor | 0.934 | 0.974 | 0.985 | 0.99 | 0.992 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
OCZ Z Series 850 W can really deliver its labeled wattage at high temperatures.
Efficiency is the highlight of this unit, as you can assume. We saw efficiency between 87.7% and 89.6% when we pulled up to 80% of its labeled wattage, i.e., up to 680 W. At full load (850 W) efficiency dropped a little bit to 86.7%, still a remarkable performance, very close to what is promised by 80 Plus Gold certification (87% at full load). As we have been exhaustively explaining in our reviews, Ecos Consulting, the company behind 80 Plus, tests power supplies at 23° C, while we test them between 45° C and 50° C, and efficiency drops with temperature. Therefore our tests are more rigorous (and more realistic) that those conducted in order to get the 80 Plus certification (click here to learn more).
Voltage regulation was very good, with all voltages within 3% of their nominal values (i.e., voltages closer to their “face value” than required by the ATX12V specification that allows a 5% tolerance for all positive voltages and 10% for -12 V). The exception was for +3.3 V during tests four and five, but still inside the 5% tolerance set by the ATX12V specification. Interesting enough we saw the exact same behavior on the 1,000 W model, so this is definitely something project-related.
Noise and ripple was always low, except on -12 V output, which was practically touching the maximum allowed at 113.4 mV. Once again we saw the exact same behavior on the 1,000 W model, so this is definitely something related to the project of these units.
Below you can see the results for the other outputs on the same test. The maximums allowed are 120 mV for +12 V and -12 V and 50 mV for +5 V and +3.3 V. All values are peak-to-peak figures.
Figure 17: +12VA input from load tester during test five at 842.1 W (56.8 mV).
Figure 18: +12VB input from load tester during test five at 842.1 W (52.2 mV).
Figure 19: +5V rail during test five at 842.1 W (14.2 mV).
Figure 20: +3.3 V rail during test five at 842.1 W (23.4 mV).
Let’s see if we could pull even more from OCZ Z Series 850 W.