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[nextpage title=”Introduction”]

Zalman has just released a new power supply line, the HP Plus, featuring two internal heatpipes and modular cabling system. Currently only two models are available, 850 W and 1,000 W, both with 80 Plus Silver certification. Although they are not selling them yet, Zalman has already got 80 Plus Bronze certification for the 500 W, 600 W, and 700 W models, so they will be releasing these models in the near future. Let’s see if the 850 W model is a good buy.

Models from the original Zalman HP series below 850 W were manufactured by FSP, while the models 850 W and 1,000 W models were manufactured by Enhance Electronics, and the new HP Plus 850 W and 1,000 W models continue to be manufactured by Enhance Electronics.

Zalman ZM850-HP Plus power supplyFigure 1: Zalman ZM850-HP Plus power supply

Zalman ZM850-HP Plus power supplyFigure 2: Zalman ZM850-HP Plus power supply

The Zalman ZM850-HP Plus is huge, being 8.3” (210 mm) deep. It comes with a 140 mm dual ball bearing fan (Zalman ZF1425ATF) on its bottom.

The new Zalman ZM850-HP Plus has a modular cabling system with eight connectors. The power supply comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector,20.9” (53 cm) long, permanently attached to the power supply
  • One cable with two ATX12V connectors that together form an EPS12V connector, 21.3” (54 cm) long, permanently attached to the power supply
  • One cable with one six-pin connector and one eight/six-pin connector for video cards, 19.7” (50 cm) to the first connector and 5.5” (14 cm) between connectors, permanently attached to the power supply
  • Two cables with one six-pin connector and one eight/six-pin connector for video cards each, 20” (51 cm) to the first connector and 5.5” (14 cm) between connectors, modular cabling system
  • Three cables with three SATA power connectors each, 19.7” (50 cm) to the first connector, 5.5” (14 cm) between connectors, modular cabling system
  • One cable with three standard peripheral power connectors, 23.6” (50 cm) to the first connector, 5.5” (14 cm) between connectors, modular cabling system
  • One cable with two standard peripheral power connectors and one floppy disk drive power connector, 23.6” (50 cm) to the first connector, 5.5” (14 cm) between connectors, modular cabling system
  • One fan power adapter with two outputs, high speed (+12 V) and low speed (+5 V), to be attached to any standard peripheral power connector

The cables with SATA and peripheral power connectors use 18 AWG wires, but the main motherboard cable, the EPS12V/ATX12V cables and the video card cables use thicker 16 AWG wires, which is always nice to see.

The number of connectors and cable configuration is perfect for an 850 W product, and it was nice to see the presence of six video card power connectors instead of the traditional four, allowing you to install up to three high-end video cards at the same time without using adapters. The number of SATA power connectors (nine) is satisfactory, but we’ve seen competing 850 W units with 12 of them.

Zalman ZM850-HP Plus power supplyFigure 3: Cables

Let’s now take an in-depth look inside this power supply.

[nextpage title=”A Look Inside The Zalman ZM850-HP Plus”]

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Zalman ZM850-HP Plus power supplyFigure 4: Top view

Zalman ZM850-HP Plus power supplyFigure 5: Front quarter view

Zalman ZM850-HP Plus power supplyFigure 6: Rear quarter view

Zalman ZM850-HP Plus power supplyFigure 7: Printed circuit board

[nextpage title=”Transient Filtering Stage”]

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

The Zalman ZM850-HP Plus has all the required components, plus two additional Y capacitors, two additional X capacitors, and two X capacitors after the rectifying bridge.

Zalman ZM850-HP Plus power supplyFigure 8: Transient filtering stage (part 1)

Zalman ZM850-HP Plus power supplyFigure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion about the components used in the Zalman ZM850-HP Plus.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Zalman ZM850-HP Plus. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one BU1506 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 15 A at 100° C so, in theory, you would be able to pull up to 1,725 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out. Of course, we are only talking about this component, and the real limit will depend on all the other components in this power supply.

Zalman ZM850-HP Plus power supplyFigure 10: Rectifying bridge

The active PFC circuit uses two STW25NM50N MOSFETs, which are capable of delivering up to 22 A at 25° C or up to 14 A at 100° C (note the difference temperature makes) in continuous mode, or up to 88 A in pulse mode at 25° C, each. These transistors present a 140 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two capacitors with the same total capacitance are physically smaller than a single capacitor with equivalent capacitance. The Zalman ZM850-HP Plus uses two 270 µF x 420 V capacitors connected in parallel, the equivalent of one 540 µF x 420 V capacitor. They are Japanese, manufactured by Rubycon, and labeled at 85° C.

In the switching section, another two STW25NM50N MOSFET transistors are used, installed in the traditional two-transistor forward configuration.

Zalman ZM850-HP Plus power supplyFigure 11: Switching transistors and active PFC diode and transistors

The primary is controlled by the CM6802 active PFC/PWM combo controller.

Zalman ZM850-HP Plus power supplyFigure 12: Active PFC/PWM combo controller

Now let’s take a look at the secondary of this power supply.

[nextpage title=”Secondary Analysis”]

This power supply has three Schottky rectifiers and four MOSFET transistors attached to the secondary heatsink.

The maximum theoretical current each line can deliver is given by the formula I / (1 – D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output uses a synchronous design. In this kind of design, the manufacturer replaces the rectifiers with MOSFET transistors in order to increase efficiency. In this power supply, four AOT480 transistors are used, each one capable of handling up to 180 A at 25° C or up to 134 A at 100° C in continuous mode, or up to 500 A at 25° C in pulse mode, with an RDS(on) of only 4.5 mΩ.

The +5 V output uses one STPS60L45CW Schottky rectifier (60 A, 30 A per internal diode at 135° C, maximum voltage drop of 0.73 V), giving us a maximum theoretical current of 43 A or 214 W for this output.

The +3.3 V output uses another STPS60L45CW Schottky rectifier, giving us a maximum theoretical current of 43 A or 141 W for this output.

Zalman ZM850-HP Plus power supplyFigure 13: +12 V transistors, +5 V, +3.3 V, and +5VSB rectifiers

The third Schottky rectifier is used by the +5VSB output.

The secondary is monitored by a PS232S integrated circuit. This chip supports over voltage protection (OVP), under voltage protection (UVP), over temperature protection (OTP), and six over current protection (OCP) channels (four +12 V, one +5 V and one +3.3 V), matching the number of +12 V rails advertised by the manufacturer (four). We could clearly see shunts (current sensors) attached to each +12 V rail.

Zalman ZM850-HP Plus power supplyFigure 14: Monitoring circuit

All electrolytic capacitors used in the secondary are from Teapo and labeled at 105° C.

[nextpage title=”Power Distribution”]

In Figure 15, you can see the power supply label containing all the power specs.

Zalman ZM850-HP Plus power supplyFigure 15: Power supply label

This power supply has four  +12 V virtual rails, and we could confirm this by the presence of individual over current protection circuits attached to each rail (see Figure 16). Click here to learn more about this subject.

Zalman ZM850-HP Plus power supplyFigure 16: “Shunts” (current sensors)

These rails are distributed like this:

  • +12V1 (yellow/black wire): One of the ATX12V connectors (half of the EPS12V connector), one of the video card cables from the modular cabling system, peripheral power connectors
  • +12V2 (solid yellow wire): Main motherboard cable, one of the ATX12V connectors (half of the EPS12V connector)
  • +12V3 (yellow/blue wire): The video card cable that is permanently attached to the power supply
  • +12V4 (yello
    w/green wire): One of the video card cables from the modular cabling system, SATA power connectors

With four rails and three video card cables, the manufacturer should have put each video card cable on a separate rail and the CPU on the fourth rail. However, they split the CPU power connector in two separate rails, making half of the EPS12V connector to be mixed with one of the video card cables. So, for a better power distribution, we recommend you to use the video card cable that is permanently attached to the power supply and the connector of the modular cabling system that is closer to the cables that are permanently attached to the power supply, as this is the connector attached to the +12V4 rail, avoiding the connector that is available in the middle of the modular cabling system, which is the one that shares the rail with the EPS12V connector.

Let’s now see if this power supply can really deliver 850 W.

[nextpage title=”Load Tests”]

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 the behavior of the reviewed unit 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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. In 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 our tests, the +12VA input was connected to the power supply +12V1, +12V2 and +12V3 rails, while the +12VB input was connected to the power supply +12V1 and +12V2 rails (EPS12V connector).

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12VA 6 A (72 W) 13 A (156 W) 18.5 A (222 W) 25 A (300 W) 32 A (384 W)
+12VB 6 A (72 W) 12 A (144 W) 18.5 A (222 W) 25 A (300 W) 32 A (384 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 (19.8 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 170.6 W 342.4 W 501.7 W 670.7 W 850.4 W
% Max Load 20.1% 40.3% 59.0% 78.9% 100.0%
Room Temp. 44.0° C 44.5° C 47.4° C 46.4° C 46.1° C
PSU Temp. 46.8° C 46.9° C 47.6° C 49.7° C 51.2° C
Voltage Regulation Pass Pass Pass Failed at +3.3 V Failed at +3.3 V
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 200.2 W 393.8 W 580.4 W 791.0 W 1029.0 W
Efficiency 85.2% 86.9% 86.4% 84.8% 82.6%
AC Voltage 113.8 V 111.6 V 110.5 V 108.1 V 104.2 V
Power Factor 0.958 0.984 0.991 0.992 0.994
Final Result Pass Pass Pass Fail Fail

The Zalman ZM850-HP Plus can really deliver its labeled wattage at high temperatures.

Efficiency was between 82.6% and 86.9% during our tests, a decent number but below what is promised by the 80 Plus Silver certification. We see this problem happening all the time: since data for the 80 Plus certification are collected at only 23° C, we see lots of products not being able to present the same efficiency level at high temperatures, since efficiency drops with temperature.

The positive voltages stayed within a tighter 3% regulation during tests one and two, but during test three the +3.3 V exited this tighter regulation, but was still within the proper range. During tests four and five, however, the +3.3 V output existed the proper range, at +3.12 V during test four and at +3.08 V during test five (the minimum allowed is +3.135 V), making this power supply to fail our tests.

Noise and ripple levels, on the other hand, were very low. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for the +12 V and -12 V outputs, and 50 mV for the +5 V, +3.3 V, and +5VSB outputs. All values are peak-to-peak figures.

Zalman ZM850-HP Plus power supplyFigure 17: +12VA input from load tester during test five at 850.4 W (37.2 mV)

Zalman ZM850-HP Plus power supplyFigure 18: +12VB input from load tester during test five at 850.4 W (45.6 mV)

Zalman ZM850-HP Plus power supplyFigure 19: +5V rail during test five at 850.4 W (14.8 mV)

Zalman ZM850-HP Plus power supplyFigure 20: +3.3 V rail during test five at 850.4 W (10.0 mV)

Let’s see if we can pull even more from the Zalman ZM850-HP Plus.

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the unit would shut down, which is the desired behavior. During this test, however, the +3.3 V was way below the minimum allowed, at only +2.96 V, and the +5VSB was at +4.72 V (the minimum allowed is +4.75 V). The efficiency below 80% shows us that the unit was already running above its limits.

Input Overload Test
+12VA 33 A (396 W)
+12VB 33 A (396 W)
+5V 20 A (100 W)
+3.3 V 20 A (66 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 944.0 W
% Max Load 1
11.1%
Room Temp. 44.4° C
PSU Temp. 46.4° C
AC Power 1,197 W
Efficiency 78.9%
AC Voltage 100.1 V
Power Factor 0.994

[nextpage title=”Main Specifications”]

The specs of the Zalman ZM850-HP Plus include:

  • Standards: ATX12V 2.3
  • Nominal labeled power: 850 W
  • Measured maximum power: 944 W at 44.4° C ambient
  • Labeled efficiency: 85% minimum at light (20%, i.e. 170 W) and full loads, 87% minimum at typical (50%, i.e. 425 W) load, 80 Plus Silver certification
  • Measured efficiency: Between 82.6% and 86.9% at 115 V (nominal, see complete results for actual voltage)
  • Active PFC: Yes
  • Modular Cabling System: Yes
  • Motherboard Power Connectors: One 20/24-pin connector, two ATX12V connectors that together form an EPS12V connector (permanently attached to the power supply)
  • Video Card Power Connectors: Three six-pin connectors and three six/eight-pin connectors on three cables, one permanently attached to the power supply and two on the modular cabling system
  • SATA Power Connectors: Nine on three cables (modular cabling system)
  • Peripheral Power Connectors: Five on two cables (modular cabling system)
  • Floppy Disk Drive Power Connectors: One
  • Protections (as listed by the manufacturer): Over voltage (OVP), under voltage (UVP), over current (OCP), over temperature (OTP), and short-circuit (SCP) protections
  • Are the above protections really available? Yes
  • Warranty: Three years
  • More Information: https://www.zalman.com
  • Average Price in the US*: USD 210.00

* Researched at Newegg.com on the day we published this review.

[nextpage title=”Conclusions”]

The new Zalman ZM850-HP Plus disappointed us. It failed our tests by presenting a voltage below the minimum allowed on its +3.3 V output. On the other hand, noise and ripple levels were always low.

Efficiency was between 82.6% and 86.9%, which is the second problem with this power supply: at full load it can’t deliver its promised efficiency (85%) at real-world temperatures (it achieved 82.6% at 46.1° C during our 850 W test). This shouldn’t be taken so seriously we’ve seen this happening all the time.

But what really kills this power supply is its price. At USD 210 it is more expensive than products that are better, such as the XFX 850 W Black Edition (USD 150, 80 Plus Silver), the Corsair HX850W (USD 170, 80 Plus Silver), and the Seasonic X-Series 850 W (USD 200, 80 Plus Gold). So, even if the Zalman ZM850-HP Plus had passed our tests we wouldn’t be able to recommend it.