Topology selector
DX, CDW, CHW or liquid? The right answer in three steps.
Tell us your load profile, the plant infrastructure available, and your uptime target. We'll recommend the topology that fits, flag the design risks, and call out alternates worth pricing.
Step 1 · Load profile
Sensible kW from heat-load calculator
Highest single-rack load. >15 kW triggers high-density topology.
Step 2 · Site infrastructure
Existing CHW available?
For condensers / cooling towers
Concurrent maintainability
Step 3 · Uptime target
Recommended topology
CDW (condenser water) with cooling tower
N+1 configuration with shared condenser-water loop.
Why this topology
- ●No CHW plant available — CDW is the next best topology for medium-large data halls.
- ●Cooling tower handles heat rejection at higher efficiency than distributed DX condensers.
- ●Multiple CRAC units share the tower, making N+1 cheaper than parallel DX outdoor units.
Site flags
- ▲Cooling tower needs water-treatment program (Legionella mitigation under AS/NZS 3666).
- ▲Plant room space for primary/secondary pumps and tower piping.
Worth comparing
If the site has limited outdoor space and the load is below 200 kW, a high-efficiency DX with R-32/R-454B refrigerant remains viable but with a lifecycle penalty.
We will validate against your envelope, plant space, refrigerant phase-out obligations and capital budget — full BoM and commissioning plan in one business day.
The five topologies
Quick reference
DX (direct expansion). Refrigerant runs from the indoor cooling unit to an outdoor condenser. Most cost-effective under 50 kW. No plant build. Limited at high density.
CDW (condenser water). Indoor units reject heat to a shared cooling-water loop, typically connected to a cooling tower. Better efficiency at scale than distributed DX. Needs water treatment.
CHW (chilled water). Central chiller plant produces chilled water, distributed to perimeter or in-row CRAC units. Best efficiency above 300 kW. Adds plant complexity but enables free-cooling.
In-row. Cooling units sit between IT racks, removing heat at the source before it mixes with the room air. Critical for densities above 10 kW per rack. Pairs with hot/cold-aisle containment.
RDHx (rear-door heat exchangers).Passive coils mount to the back of a rack, cooling exhaust air with chilled or condenser water. Effective for 15-30 kW per rack. Adds rack depth.
Direct-to-chip liquid. Water or dielectric fluid runs to cold plates mounted directly on CPUs and GPUs. The only option above 30 kW per rack. Requires specialist consultancy and leak-proof loop design.