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Zalman ZM1000-HP (1000W)

The last product in this review comes from Zalman and its distinguishing feature is the use of heat pipes. As far as I know, this is the only PSU series to be equipped with such cooling technology. Some time ago I reviewed the ZM850-HP and was pleased with it. Now, let’s take a look at the higher-wattage model.

Exterior Design

The PSU is large but, unlike the Tuniq Ensemble, has only one cooling fan. The free area of the front panel is perforated for free flow of air.

The ZM1000-HP is a modular power supply. There are eight connectors for detachable cables at its back panel. The connectors are Molex Mini-Fit Jr., the same as are used in most other modular PSUs.

There is a Standby Noise Suppressor switch next to the connectors. When turned on, it loads the output of the standby source with a 20Ohm resistor. Otherwise, the standby source might hiss unpleasantly when idle. The Noise Suppressor is off by default in order to reduce the PSU’s idle power draw by about 1.5W (that’s a negligible amount, but the manufacturers are struggling to cut power consumption as much as possible nowadays). If you connect the PSU to your computer and hear no hiss, you don’t have to turn the Suppressor on (you can connect the PSU to the mains without connecting it to the mainboard for the comparison’s sake: the standby source load is zero then and my sample would produce a distinct hiss which vanished when I turned the Suppressor switch on).

The PSU is equipped with the following cables and connectors:

  • Mainboard cable with a 20+4-pin connector (49cm)
  • CPU cable with a 4+4-pin connector (50cm)
  • Two graphics card cables with one 6+2-pin connector on each (50cm)
  • One cable with three Molex connectors (49+15+15cm)
  • One cable with three SATA power plugs (49+15+15cm)
  • Two connectors for additional graphics card cables
  • Two connectors for additional PATA power cables
  • Two connectors for additional SATA power cables

Included with the PSU are:

  • Two graphics card cables with one 6-pin connector on each (50cm)
  • One cable with three Molex connectors (50+15+15cm)
  • Two cables with two Molex connectors and one floppy-drive plug on each (50+15+15cm)
  • Three cables with three SATA power plugs on each (50+15+15cm)

The only problem I can see here is that the cables are rather short. In a now-fashionable system case with cables hidden behind the mainboard and a bottom position of the PSU, the 50-centimeter CPU power cable just won’t reach to the mainboard. Besides, the PSU has only two pairs of connectors for graphics cards whereas most other PSUs offer three pairs. Of course, few users install three top-end graphics cards into their systems, but when you buy a 1000W PSU, you want to get everything possible with it.

Interior Design

It is hard but possible to identify this PSU as an Enhance product. Instead of Enhance’s massive and ribbed T-shaped heatsinks for cooling transistors and diodes, there are heat pipes secured with screws to heatsinks that have no ribbing at all. The pipes have thermal grease at the places of contact.

At the other end of the pipes there are heatsinks consisting of thin aluminum plates. The air flow from the PSU should go through these heatsinks and ensure better cooling than with ordinary heatsinks. I doubt the efficiency of this solution, though. Such heatsinks produce additional aerodynamic resistance and the air will bypass them rather than go through. We’ll discuss the cooling efficiency shortly, though.

Teapo capacitors are installed at the PSU’s output.

Additional high-frequency filters are fastened on the bunches of cables that go out of the PSU. Each filter consists of two halves of a ferrite tube in a plastic casing. Sometimes they begin to produce an irritating hiss when the load changes. If you have this problem, you can solve it by dismantling the PSU and removing the filters from the cables (you can unlock them with a thin-tipped screwdriver or knife). This will have no effect on the stability of the PSU. You can also try to fill the filter with epoxide resin to make it monolithic.

Specifications

Having a total output power of 1000W, the PSU can yield up to 960W via its +12V rail divided into six “virtual” output lines with max currents of 18A or 28A. As the table on the label shows, the more powerful lines refer to the fixed graphics card cables (with 6+2-pin connectors), which is reasonable. It is graphics cards that are the most voracious consumers in modern PCs. It should be noted that this load capacity (over 300W!) allows to place two power connectors on each cable, so the PSU might have three rather than two pairs of connectors.

UPS Compatibility

Together with an APC SmartUPS SC 620 this power supply worked at loads up to 400W when powered by the mains and up to 300W when powered by the batteries (if the load was higher than 300W, the UPS would shut down instantly). Thus, a UPS with sinusoidal output voltage and a reserve of wattage is recommended for the ZM1000-HP.

Output Voltage Stability

The PSU delivers very stable voltages: they only deflect more than 3% from the nominal values under extremely high loads (the allowable deflection being 5%).

Output Voltage Ripple

The output voltage ripple is much lower than the permissible limit at full load. Even the individual short spikes don’t spoil the overall picture.

Noisiness

The PSU is cooled by a 140x140x25mm fan that is marked as Zalman’s product. I guess the fan is actually made by some other firm, but I can’t identify it.

The fan is rotating at only 720-730rpm at loads up to 800W, making the one of the quietest PSUs in this review. It is second only to the Enermax Revolution 85+ whose fan is working at an even lower speed under low loads. On the other hand, the Zalman heats up a lot: the temperature of the air increases by 20 degrees in it.

The measurements might have been affected by the specific position of the heatsinks. I measure the air temperature at one spot, so the result may be higher if a hot stream of air hits that very spot. But there is no alternative as measuring the temperature at multiple spots would take much more time. Measuring the temperature of heatsinks as some other test labs do is even less accurate because the result depends on the particular spot and how hard the thermocouple is pressed to the heatsink. Besides, such measurements must be performed with the PSU’s cover on, which makes it hard to place the thermocouple and control how well it fits.

Efficiency and Power Factor

The PSU is 88% efficient at the maximum and over 83% efficient at full load. That’s a good result.

Standby Source

The ZM1000-HP’s standby source is rated for a rather low current of 3.5A and copes with its job well.

Summary

The Zalman ZM1000-HP is an interesting product. I don’t know how much the heat pipes contribute to it, but it is indeed one of the two quietest PSUs in this review. Unfortunately, the overall impression is somewhat spoiled by minor drawbacks. First, I guess a 1000W power supply should have more and longer cables. Second, the ferrite filters on the output cables begin to hiss under some loads in some samples of the PSU. Well, if you don’t run three graphics cards but want a quiet and high-wattage PSU, the ZM1000-HP will be a good choice, especially if you are not afraid of opening it up and removing the filters.

 
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