Dell XPS 730 H2C Performance Gaming System

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The H2C Cooling System Dissected

The original H2C (aka. H2Ceramic) cooling system first began shipping with the XPS 710 and it was Dell's first implementation of liquid cooling in a consumer product. It isn't a cut-and-dry watercooling solution, rather it's a hybrid two-stage system that incorporates a TEC element to increase cooling capacity. This was new territory, at the time, for Dell so they sought the advice of Delphi and CoolIT Systems to help them design the unit.

Dell leveraged Delphi's automobile component manufacturing experience and they provided consulting and manufacturing of the radiators and tubing used in the H2C. The TEC units used by the H2C were designed and provided by CoolIT Systems, a manufacturer of various liquid and hybrid cooling solutions for OEMs and the after-market. All these elements came together to make a fairly efficient and compact cooling unit that handled the factory overclocked quad-core processors in the XPS 710/720s with ease.

While the original H2C unit was very well suited for use in a Dell built and configured system, for which it was specifically designed, it was a bit too custom. The entire unit was rigid and self-contained. There was no way to use the unit with anything other than a XPS 710/720 with a Dell BTX motherboard. This became a problem when Dell designed the XPS 730 since it's meant to be ATX compatible and user upgradeable. One of the design goals of the XPS 730 was to allow the chassis to be as accommodating and universally compatible as any third-party chassis available on the market. This simply could not be achieved with the original H2C design so Dell sought the help of Delphi and CoolIT Systems again and went back to the drawing board.

The New & Improved H2Ceramic System
Dell's Second Generation Hybrid 2-Stage Liquid Cooling Solution

We won't go into detail on how the H2C system works but you can refer to our review of the XPS 710 H2C for a description of how the original H2C system functions. The second generation H2C functions in the same general way as the original; it is still a two-stage, TEC assisted liquid cooling unit. However, Dell has added a few additional features that greatly increase the H2C's utility and compatibility. We will mostly be focusing on the changes and additions found in the second generation unit in this article.

H2Ceramic Hybrid Cooling System (Front & Back)

The most obvious change to the H2C is a complete restructuring and redesign of the shell that holds all of its components. The second generation H2C features a split design where the cold-plate unit is separate from the heat exchanger unit, as opposed to the rigid all-in-one design of the original. This allows for greater flexibility in cold-plate placement, which is necessary since not all motherboards position the CPU socket in the same place. The cold-plate unit is connected to the heat exchanger unit by a set of flexible hoses so the whole unit is free to be adjusted as needed.

Another obvious addition to the new H2C unit is cooling support for the chipset. The original H2C unit only cooled the CPU. The second generation H2C now has a secondary cold-plate for cooling the chipset. As we saw on the previous page, the northbridge and southbridge chips on the nForce 790i Ultra SLI motherboard that ships with the XPS 730 are connected together by heatpipes. The finned top part of the heatsink over the northbridge is actually removable to allow the chipset cold-plate from the H2C unit to be connected. In this fashion, the single chipset cold plate is able to cool both the northbridge and the southbridge. Unfortunately, most after-market motherboards do not have this feature so only the northbridge can be cooled. However, the southbridge produces relatively little heat so this shouldn't be a big issue.

The XPS 730 is only available with Intel processors so the H2C unit is only required to support Socket T (LGA 775) that is used by all modern Intel processors. However, the next generation of Intel processors will move to a new processor socket that is larger and not compatible with Socket T. In order to maintain compatibility for future upgrading, Dell has designed the cold-plate mounting mechanism to be reconfigurable to support Socket 1366, which will be used by the upcoming next generation of Intel processor, code-named Nehalem. This ensures the H2C can be used with new platforms for the foreseeable future. The standard XPS 730 air cooler will also have this compatibility feature.

The last compatibility feature added to the second generation H2C is the addition of a small fan to one side of the cold-plate unit. This fan is meant to blow onto the generally passive heatsinks that cool the voltage regulation circuitry next to the processor socket. On many motherboards, these heatsinks depend on the residual airflow from the fan on the processor heatsink to cool them. Since the H2C system is liquid based and doesn't need a processor fan, there is little airflow in that area which can lead the voltage regulator circuitry to overheat in some designs. The small fan provides the airflow needed to ensure this does not happen.

H2Ceramic Cooling System Cold Plate Unit (CPU & Chipset Cold Plates)

Liquid cooling systems are generally fairly high maintenance compared to air cooling. This is largely due to the need to periodically refill the system. Over time, the liquid within the system will slowly escape by permeating through the tubing, joints and other components. This means the liquid level in the system is constantly dropping, although at an extremely slow pace, usually on a time-scale of months. Since the water is escaping so slowly, it evaporates before enough of it has collected to form a droplet so there is no danger of short circuiting the electronics in your computer. However if the water level within the system drops too much, it could lead to pump failure and overheating.

Most liquid cooling systems use surgical silicon tubing and it is the preferred tubing material for enthusiasts since it is cheap, easy to work with and clear. Unfortunately, silicon is fairly permeable and it allows enough water so seep through that most liquid cooling systems would need to be topped off with more liquid within a few weeks, unless a liquid reservoir is used to act as a buffer. Even with a reservoir, refilling would still be necessary after a few months to a year.

Dell's solution to this problem is to use re-enforced plastic tubing, the same type used in cars. Compared to silicon tubing, plastic tubing is very low permeation and very little liquid escapes as a result. The tubing used in the H2C is thick and re-enforced with crosshatched ribs to prevent kinking. All connections and joints are barbed and the re-enforcing ribs help the tubing lock on to the connection barbs to form an extremely tight seal that is quite strong. Just to make doubly sure that there is no chance of leaks, Dell also uses hose-clamps on all connections.

H2Ceramic Cooling System 2-Stage Heat Exchanger Unit (TEC Element & Radiator)

The pump used in the second generation H2C is very similar to the original. It is still a hybrid unit with a built-in reservoir with a spring-loaded floor. The reservoir ensures the system has some 'extra' water available which comes in handy over long periods of time as some of the water inevitably escapes from the system. The spring-loaded floor maintains water pressure and ensures that a vacuum or worse, an air bubble is not created within the system. The pump speed is now dynamically controlled. The original pump used in the first generation H2C always operated at 100% power, which is unnecessary when the system is idle.

Dell claims that the plastic tubing in combination with the reservoir allows to system to remain completely maintenance free for at least 7 years; a very long time in computer terms.

As with the original H2C system, the second generation unit does not support graphics card cooling. According to Dell, this is because the heatsink mounting mechanisms used on graphics card aren't as standardized as CPU cooling so it is very difficult to anticipate future graphics products to ensure that the H2C will be compatible.

Overall, the second generation H2C cooling system is significantly more impressive than the original. While it functions in the same general way and performance is likely to be similar since it still uses a single 120mm radiator, the new features and compatibility greatly enhances the utility and life-span of the unit.

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