When air stops keeping up
In data centers and other high-density computing spaces, air cooling has a ceiling. As rack densities climb to support high-performance computing and modern GPU hardware, there comes a point where moving enough air through a space stops being practical — the fans get louder, the aisles get harder to manage, and the heat still isn’t leaving fast enough.
Liquid cooling is the usual answer at that point, because water moves heat far more effectively than air does. But it introduces a question that air cooling never had to deal with: how do you get facility water to a rack without putting facility water inside the rack?
That’s the job of a Coolant Distribution Unit.
What a CDU does
A Coolant Distribution Unit, or CDU, sits between two separate cooling circuits and transfers heat from one to the other without letting the fluids mix.
- The primary circuit is facility side — the building’s chilled or process water.
- The secondary circuit is the clean, treated loop that actually goes out to the IT equipment.
A liquid-to-liquid CDU keeps those two circuits isolated while controlling the secondary loop’s flow, pressure, temperature, and coolant quality. That isolation is the whole point: facility water carries whatever the building’s system carries, and none of it belongs in a direct-to-chip cold plate.
Two terms worth defining, because they come up constantly in CDU specs:
- Approach temperature — the difference between the primary inlet temperature and the secondary supply temperature. A tighter approach means the CDU delivers colder water to the load for the same facility water temperature, which usually costs capacity.
- Dew point — the temperature at which moisture condenses out of the air. Circulating secondary water below the room’s dew point risks condensation on pipework and hardware, which is why CDUs monitor it.
The Delta GoCool Range
Delta Electronics is an industry leader in power and thermal management, with data center infrastructure as one of its core business segments. Their GoCool liquid-to-liquid CDU range covers two primary capacity points — the GoCool-1500 and the higher-capacity GoCool-3000. Delta positions both around the same three things: managing high-density thermal load, reducing power consumption relative to air cooling, and keeping the secondary loop clean and condensation-free over the long term.
The GoCool-1500 is rated at a nominal 1500 kW. The GoCool-3000 doubles that to a nominal 3000 kW for higher-density deployments, in a deeper footprint with larger pipe connections.
What the two units share:
- Both support direct-to-chip and Rear Door Heat Exchanger (RDHx) applications, so either can serve a mixed air-and-liquid room rather than requiring a full conversion up front.
- Redundancy is built in on both: dual power feed with an automatic transfer switch, control sensor redundancy, and pump redundancy, with the design intent of no single point of failure.
- Condensation is actively managed through a dew point monitor rather than left to room controls, and leak detection is standard with configurable alarm response.
- Both run on the same electrical supply range and speak the same protocols — SNMP, Modbus RTU, Modbus TCP/IP, and BACnet — through a 10″ colour touchscreen.
- Both use stainless steel plumbing with coolant filtration and ongoing coolant health monitoring.
Where they differ, beyond capacity:
- Capacity moves with approach temperature on both, and the curve matters more than the headline number. The GoCool-1500 is rated 1500 kW at a 6°C approach and 1016 kW at 4°C. The GoCool-3000 is rated 3000 kW at 6°C and 2000 kW at 4°C. The colder you need the secondary supply, the less capacity you get from the same box.
- Connections differ in both size and type. The GoCool-1500 uses 4″ sanitary ferrule on both sides; the GoCool-3000 uses 6″ Victaulic. This is not a detail to discover late — it changes the pipework.
- Footprint and weight scale up. The GoCool-1500 is 1200 x 1200 x 2300 mm at 1900 kg wet; the GoCool-3000 is 1200 x 1500 x 2300 mm at 2800 kg wet. Same width and height, 300 mm deeper, and nearly a tonne heavier — worth checking against your access route and floor loading.
- Filtration defaults are reversed. The GoCool-1500 ships with a 50 µm secondary filter upgradeable to 25 µm; the GoCool-3000 ships with 25 µm standard and 50 µm as an option. Both are on isolation valves for hot-swap.
- Coolant health monitoring goes further on the larger unit: the GoCool-1500 uses a pH sensor, while the GoCool-3000 adds a conductivity sensor with turbidity available as an option.
- The filling tank is optional on the GoCool-1500 and standard on the GoCool-3000.
For most single-room or first-step liquid cooling projects, the GoCool-1500 is the natural starting point. The GoCool-3000 is the answer when density or total load outruns it — and because both share controls, protocols, and redundancy philosophy, standardising on the range across a mixed-capacity site is straightforward.
A drive question underneath a cooling question
Worth noting for anyone who knows BlueRock for motors and drives: the GoCool-1500 runs variable frequency drives on its pumps as standard equipment.
That’s not incidental. Pump speed control is what lets a CDU match flow to actual thermal load instead of running flat out, and it’s a large part of where the energy savings come from. It also means the failure modes and commissioning questions on the pumping side will look familiar to anyone who has worked through a VFD-driven pump application before — which is squarely the kind of work BlueRock supports every day.
What to confirm before you spec one
A CDU is a plumbing, electrical, structural, and controls decision at the same time. Before committing to a unit, confirm:
- Approach temperature target and the resulting capacity — work backwards from the secondary supply temperature your hardware needs, not from the headline kW figure. This is also what decides whether you need the 1500 or the 3000.
- Primary water availability and temperature — nominal ratings assume a 17°C primary inlet, at 1300 LPM for the GoCool-1500 and 3000 LPM for the GoCool-3000. Confirm the facility side can actually deliver it.
- Secondary fluid — both units are rated on 25% propylene glycol, not plain water. Confirm your loop matches.
- Pressure budget — external pressure drop on the secondary side is 331 kPa on the GoCool-1500 and 334 kPa on the GoCool-3000, and it has to fit the loop you’re feeding.
- Electrical supply — 380/400/415/480 Vac, 3P3W+PE, 50/60 Hz, with a 342–528 Vac operating range on both, and confirm the top-mounted power feed suits the room.
- Space, access, and floor loading — 1200 mm front and 800 mm rear clearance on both, but the units differ: 1200 x 1200 x 2300 mm at 1900 kg wet for the GoCool-1500, versus 1200 x 1500 x 2300 mm at 2800 kg wet for the GoCool-3000.
- Piping and connections — 4″ sanitary ferrule on the GoCool-1500, 6″ Victaulic on the GoCool-3000, connected at the top on both.
- Monitoring integration — SNMP, Modbus RTU, Modbus TCP/IP, and BACnet are supported on both; confirm what your BMS actually speaks.
- Noise — the GoCool-1500 is rated under 76 dBA at 1 m. Delta lists the GoCool-3000 figure as still to be released, so confirm it with us before siting the larger unit anywhere noise-sensitive.
Available through BlueRock
BlueRock has both the Delta GoCool-1500 and the higher-capacity GoCool-3000 available, and can help work through sizing, integration, and the questions above before anything is ordered.
If you’re evaluating liquid cooling for a high-density load — or trying to work out whether a CDU is the right answer at all — BlueRock can help sort through the options. Our value isn’t just supplying the unit; it’s helping assess the application and follow through.
Spec Reference
| Item | GoCool-1500 | GoCool-3000 |
| Nominal cooling capacity | 1500 kW @ 6°C • 1375 kW @ 6°C • 1250 kW @ 5°C • 1016 kW @ 4°C | 3000 kW @ 6°C • 2500 kW @ 5°C • 2000 kW @ 4°C |
| Primary side | Water • 1300 LPM at 17°C • 114 kPa • 500 µm filter w/ bypass loop | Water • 3000 LPM at 17°C • 159 kPa • 500 µm filter |
| Secondary side | 25% PG • 1524 LPM • 4°C approach • 50 µm (upgradeable to 25 µm) • 331 kPa external | 25% PG • 3000 LPM • 4°C approach • 25 µm (optional 50 µm) • 334 kPa external |
| Power supply | 380/400/415/480 Vac, 3P3W+PE • 342–528 Vac • 50/60 Hz • dual feed + ATS | Same as GoCool-1500 |
| Dimensions (W x D x H) | 1200 x 1200 x 2300 mm | 1200 x 1500 x 2300 mm |
| Net weight | 1900 kg wet / 1600 kg dry | 2800 kg wet / 2222 kg dry |
| Clearance | Front 1200 mm • rear 800 mm | Front 1200 mm • rear 800 mm |
| Connections | 4″ sanitary ferrule, both sides • top entry | 6″ Victaulic, both sides • top entry |
| Noise level | < 76 dBA at 1 m | To be released by Delta |
| Communications | 10″ touchscreen • SNMP, Modbus RTU, Modbus TCP/IP, BACnet | Same as GoCool-1500 |
| Pump redundancy | 3+1 (N+1) or 4 (N mode) | N modes |
| Coolant health | pH sensor | pH + conductivity sensors • optional turbidity |
| Filling tank | Optional | Standard |
| Standard on both | Leak detection • dew point monitor • VFDs • expansion vessel • auto-restart • control sensor redundancy • grouping control | Leak detection • dew point monitor • VFDs • expansion vessel • auto-restart • control sensor redundancy • grouping control |
| Conformance | CE, UL/CSA 60335 | CE, UL/CSA 60335 |