The Zalman ZM1200-EBT 1200W Power Supply Review

Hot Test Results

As seen below, the Zalman ZM1200-EBT provides acceptable power quality for a high quality PSU. The voltage regulation is excellent, with the 12V line maintaining its potential output within 1.8% across the nominal load range. The 3.3V/5V lines are even better regulated, maintaining their voltage potential within just 1.1%. 

However, we did not find the filtering to be as good, with a maximum ripple of 74 mV on the 12V line. The filtering is even worse on the better regulated minor lines, reaching a maximum of 42 mV on the 3.3V line with a suggested design limit of 50 mV. Although these figures are not extraordinary by today's standards, they are satisfactory for a modern 1200W PSU.

Zalman rates the output of the ZM1200-EBT at 50 °C ambient and therefore it did not have a problem reaching its maximum power output inside our hotbox. There is however a significant impact on the energy conversion efficiency, with average nominal load (20-100%) efficiency dropping down to 90.5%. The efficiency drop seems to be slightly more significant at higher loads, hinting that the components are becoming thermally stressed under these conditions. The maximum efficiency drops down to 91.9% at 50% load and the minimum efficiency within the nominal load range is 89.3% at 100% load.

The acoustic profile of the ZM1200-EBT changes significantly once the PSU is found inside a very hot environment. The fan is silent only while the PSU is minimally loaded, with its speed increasing quickly alongside with the load in order to keep up with the high cooling demands of the unit. Once the load reaches 80% of the unit's capacity, the fan essentially operates at maximum speed, reaching painful noise output levels. However, despite the valiant efforts of the fan, the internal temperatures of the ZM1200-EBT are high for an 80Plus Gold certified unit, even for one with such a massive output, hinting that the heatsinks are just barely large enough to maintain reliable operation under such conditions.