On the downside, when an ACSC sends out e-mail notifications, expect to get several per minute during the event. Also, although centralized authentication for the management application supports RADIUS, it does not support LDAP, which is a minor annoyance. This is true not only for APC's air conditioning units, but also for most of its network-enabled products, since they all use the same base management platform. I've posted instructions on integrating APC management cards and Microsoft Active Directory authentication via Microsoft's Internet Authentication Server on my blog.

For the price, the ACSC100s are very capable cooling units that can be easily deployed in hotspots or throughout an entire datacenter, but research into the HVAC systems used in the building are a mandatory step prior to purchase and installation. If the ACSC100s are right for the building and the room, they're definitely a good investment.

InfraStruXure InRow RC
To the casual observer, the ACRC100 looks identical to the ACSC100, but it's a completely different device. Where the ACSC100 is a self-contained air conditioner, the ACRC100 has no compressor, relying on an external chiller unit to deliver cold water through top- or bottom-fed piping. And whereas installing the ACSC100 is a snap, installing the ACRC100 requires skilled mechanical labor.

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In addition to the chiller itself, the ACRC100 incorporates an external CDU (cooling distribution unit), essentially a large box containing pipe fittings and valves. Water from the chiller enters the CDU and flows through copper or plastic piping to each ACRC100. Water returning from the ACRC100 flows back into the CDU and on to the chiller unit, completing the circuit. APC recommends using flexible plastic piping, but the mechanical contractor doing the installation took one look at it and recommended more durable copper piping instead, at a minimal cost increase. The downside of copper piping is inflexibility; once piped, the ACRC100 cannot be moved, not even an inch.

The installation in this case involved four ACRC100 units. The chiller that feeds them is a 21.5-ton roof-mounted unit that consistently delivers 45-degree water to each ACRC100, which then pumps out cold air via eight front-mounted fans. Hot air is pulled from the rear of the unit and dissipated into the return water, which is then passed back to the chiller to be rechilled. The ACRC100 can deliver more than three times the cooling output of the ACSC100 (up to 30kW), and the fans push more than twice the air -- up to 2,900 CFM.

Operationally, the ACRC100s are managed much like the ACSC100s, using the same Web-based interface. Unlike the ACSC100s, multiple ACRC100s must be grouped into management realms, where they communicate with one another to dynamically alter cooling levels and output in a given row of racks or even throughout an entire datacenter.

Costs associated with the ACRC100s are significantly higher than with the ACSC100s, but the unit price is roughly the same. Expect chiller costs to run between $30,000 and $40,000, with installation running about the same. Plus, the complexities of an ACRC100 turn-up call for a trained technician will add to the overall cost.