CRX4-DLC Coolant Distribution Units
Since 2002 • 100,000+ UPS units supported • 24/7 support
What a Coolant Distribution Unit Does
The Heart of Every Direct to Chip Liquid Cooling Loop
A coolant distribution unit, or CDU, sits between the building's water and the cold plates on your GPUs and CPUs, and keeps the two apart. Facility water stays on one side of a plate heat exchanger. A clean, filtered technology loop runs on the other, through the manifolds and onto the processor.
The CDU holds temperature, flow and pressure to the chip vendor's specification, guards against condensation inside the server, and keeps facility water quality away from the fine channels in a cold plate. The CRX4-DLC range covers four CDUs: a 4U rack unit, a row cabinet for a full row of AI racks, and two liquid to air units for sites with no facility water at all.
Need a CDU sized or costed?
- Sizing against your rack load
- CDU, manifolds & heat rejection as one system
- Leak detection & monitoring included
- Install, commission & 24/7 support
Two loops, kept apart at the plate heat exchanger
Four CDUs, Chosen by Load and by Water
Two questions decide which unit you need: is there facility water at the rack, and how much heat is the liquid loop carrying. Rack and row units transfer heat into facility water through a plate heat exchanger. Sidecar units work where there is none.
Rack CDU
100 kW in 4U
Liquid to liquid. Sits in the rack it cools, with dual pumps, dual power supplies and hot swappable 48 VDC power modules.
- Needs facility water at the rack
- Suits single racks and staged builds
- 13 °C approach, 145 LPM
Best fitOne to a few liquid cooled GPU racks, each on its own unit.
Row CDU
2,020 kW at ASHRAE W2, 1,520 kW at W3
One 800 mm wide cabinet serving a full row of AI racks, at a 4 °C approach with 1,500 LPM secondary flow.
- Needs a facility water loop
- Dual pumps in N+N for 2N redundancy
- Optional automatic transfer switch
Best fitA GPU hall or a full row of rack scale accelerator platforms.
Liquid to air sidecar
80 kW
Moves heat from the liquid loop into air that your existing CRAC, CRAH or fan wall then removes. No plumbing changes to the building.
- No facility water required
- Hot swappable EC fans in N+1
- Dual pumps for 2N reliability
Best fitBringing liquid cooled servers into an existing air cooled room.
Liquid to air with DX
150 kW
A sidecar with its own dual DX system and inverter compressor, so it conditions the air it rejects into rather than relying on room capacity.
- No facility water required
- R513A refrigerant, EC fans
- 44,000 m³/h air flow
Best fitHigher loads in a room with no water and no cooling to spare.
CRX4-DLC CDU Technical Data
Every CDU in the range. The two LL-1520 columns are the same unit rated in two ASHRAE working categories, not two products.
Swipe the table sideways to see all of it
| Model | CRX4-DLC-LL-100 | CRX4-DLC-LL-1520 (W3) | CRX4-DLC-LL-1520 (W2) | CRX4-DLC-LA-80 | CRX4-DLC-LA-150DX |
|---|---|---|---|---|---|
| Cooling type | Liquid to liquid | Liquid to liquid | Liquid to liquid | Liquid to air | Liquid to air, dual DX |
| Cooling capacity | 100 kW | 1,520 kW | 2,020 kW | 80 kW | 150 kW |
| ASHRAE category | W3 | W3 | W2 | W3 liquid, A2 air | n/a |
| Dimensions (W × H × D) | 440 × 177 × 910 mm, 4U | 800 × 2200 × 1200 mm | 800 × 2200 × 1200 mm | 600 × 2200 × 1200 mm | 1200 × 2400 × 1200 mm |
| Approach temperature | 13 °C | 4 °C | 4 °C | 13 °C | n/a |
| Secondary flow | 145 LPM | 1,500 LPM | 1,500 LPM | 120 LPM | 13.6 m³/h |
| Primary side | 32 / 42 °C water | 32 / 42 °C water | 27 / 37 °C water | 27 °C inlet air | 29.5 °C return air |
| Secondary supply / return | 45 / 55 °C | 36 / 52 °C | 31 / 52 °C | n/a | 30 / 40 °C |
| Filtration | 50 µm secondary, 200 µm primary | 50 µm secondary, 200 µm primary | 50 µm secondary, 200 µm primary | 50 µm secondary | n/a |
| Secondary medium | PG25 | PG25 | PG25 | PG25 | 25% propylene glycol |
| Connections | 1.25" tri-clamp | DN100 | DN100 | DN32 | n/a |
| Power consumption | 0.5 kW | 17.8 kW | 17.8 kW | 5.8 kW | n/a |
| Power input | 110 to 240V, 1 to 2 phase | 380 to 415V, 3 phase | 380 to 415V, 3 phase | 208 to 264V, 1 phase | 380 to 415V, 3 phase |
Figures are at rated conditions and vary with water temperature and approach. Full selections are run against your loop temperatures and site.
Built into the CRX4-DLC CDUs
- Dual pumps for 2N redundancy on the rack, row and LA-80 units
- Stepless pump speed control for efficiency at part load
- Stainless steel fluid circuit with no corrosion concern
- Primary and secondary fluid filtration
- Anti-condensation logic and leak detection as standard
- Online monitoring of fluid temperature, pressure and flow
- Modbus-RTU, Modbus-TCP and webserver, SNMP optional
- Optional dual power supply and automatic transfer switch
Which CDU Fits Your Site?
Answer two questions for a starting point. Final selection is always run against your loop temperatures and the room.
1. Is there facility water at the rack row?
2. How much heat is the liquid loop carrying?
A CDU Is Only Part of the Loop
A CDU on its own does not deliver a low PUE. The result comes from matching the approach temperature, the secondary loop, the filtration and the heat rejection to the site and its climate. The CRX4-DLC platform covers every part of that loop, engineered as one system before anything is quoted.
Manifolds
316 stainless, 21 inlet and 21 outlet ports, vertical or horizontal, feeding each cold plate.
Couplings and hoses
Self-sealing dry disconnects on colour coded hoses, so lines seal on both sides when a server is pulled.
Dry coolers
Heat rejection with zero water consumption, a natural match for warm water loops.
Free cooling chillers
100 to 1,053 kW, free cooling from 5 °C ambient with automatic changeover to mechanical.
Cooling towers
Counterflow towers from 100 to 1,000 kW for sites rejecting to condenser water.
Monitoring
Fluid temperature, pressure and flow from every unit, with leak detection, into your DCIM or BMS.
A CDU Hall Still Needs Air Cooling
Cold plates capture roughly 70 to 80 percent of the heat at the processor. The other 20 to 30 percent still leaves the server as hot air, from memory, drives, network cards and power supplies. A direct to chip hall therefore needs a CDU and conventional precision cooling, sized against the same load.
See the full air range on our cooling solutions page, or how power and cooling are sized together on the GPU power and cooling page.
Why Choose UPS Solutions for CDUs
Australian owned critical power and cooling specialists. Very few suppliers here can quote the CDU, the facility loop and the power behind it on the same page, and fewer still install and maintain all of it afterwards.
Power and cooling, one scope
One party sizes the CDU, the facility water and the UPS against the same load figure and owns the interfaces between them.
We design the whole loop
CDU sizing, manifolds, leak detection, facility water and heat rejection engineered as one system, rather than a CDU sold in isolation.
Australian field team
Local technicians across Sydney, Melbourne, Brisbane, Perth, Adelaide and beyond. The people who commission your loop are the people who come back to service it.
24/7 support after handover
Preventive maintenance, coolant and filtration service, leak checks and emergency response across Australia, New Zealand and the Pacific Islands.
How a CDU Project Runs
Load and site review
Rack count, kW per rack, the accelerator platform, and whether facility water is available at the row.
CDU and loop design
CDU type and count, redundancy, manifolds and heat rejection, drawn against your loop temperatures.
Install and commission
Mechanical and electrical installed together, then the loop is tested as a system.
Monitor and maintain
Leak, flow and temperature monitoring, planned maintenance and 24/7 support.
Send us the racks, the kW and the water
Rack count, kW per rack, the platform you are deploying, and whether there is facility water at the row. That is enough for us to recommend a CDU and put a configured price in front of you.
Coolant Distribution Unit FAQs
The questions we are asked most when scoping direct to chip liquid cooling.
What is a coolant distribution unit?
A coolant distribution unit, or CDU, is the heat exchanger, pump and control set that sits between facility water and the cold plates in a direct to chip liquid cooled rack. It keeps the two loops separate, holds temperature, flow and pressure to the racks, and monitors the technology loop for leaks and faults.
Why not run facility water straight to the cold plates?
Facility water is not controlled closely enough for a cold plate. Its temperature, pressure and water quality all vary, and the channels in a cold plate are fine enough to foul. A CDU isolates the server loop through a plate heat exchanger, filters it, holds temperature, flow and pressure to the chip vendor's specification, and uses anti-condensation logic so nothing condenses inside the server.
What is the difference between a liquid to liquid and a liquid to air CDU?
A liquid to liquid CDU passes the heat into facility water, from a chiller, dry cooler or cooling tower. A liquid to air CDU needs no facility water. The CRX4-DLC-LA-80 moves the heat into air that your existing CRAC, CRAH or fan wall removes, so the room cooling must have the capacity for it. The CRX4-DLC-LA-150DX has its own dual DX system, so it conditions the air it rejects into and does not rely on room capacity.
Rack CDU or row CDU, which do I need?
A rack CDU such as the CRX4-DLC-LL-100 serves the rack it sits in, which suits single racks and staged builds. A row CDU such as the CRX4-DLC-LL-1520 serves a full row through manifolds, rated 2,020 kW in ASHRAE W2 conditions or 1,520 kW in W3, which suits a hall of liquid cooled racks. Rack count, redundancy target and floor space usually decide it.
How do I size a CDU?
Start from the heat the liquid loop will carry, not the full rack load. Cold plates capture roughly 70 to 80 percent of the heat, so the CDU is sized on that share, with the rest handled by air cooling. Facility water temperature, approach and redundancy then set the unit count. Send us the racks, the kW and the platform and we will run the selection.
Do I still need air conditioning with direct to chip cooling?
Yes. The 20 to 30 percent of heat that cold plates do not capture still leaves the server as hot air, so a direct to chip hall needs precision air cooling as well as the CDU. Immersion is the exception, because the whole server sits in fluid.
What happens if a CDU pump fails?
The rack, row and LA-80 CDUs run dual pumps for 2N redundancy, so one pump carries the full load while the other is serviced, and the rack CDU has dual, hot swappable power supply modules. Whole unit redundancy is set by CDU count at design stage, because a single CDU serving a whole row is still a single point of failure.
What does ASHRAE W2 and W3 mean on a CDU?
They are ASHRAE liquid cooling classes describing how warm the facility water supply is. W2 is cooler water than W3, so the same CDU carries more heat on W2. The CRX4-DLC-LL-1520 is rated 2,020 kW on W2 and 1,520 kW on W3. Warmer water costs capacity at the CDU but makes free cooling available for more of the year.
Can CDUs connect to our BMS or DCIM?
Yes. Every unit reports fluid temperature, pressure and flow over Modbus-RTU, Modbus-TCP and a built-in webserver, with SNMP optional, so it integrates with the DCIM or BMS your team already runs.
Can we start small and add CDUs later?
Yes. Capacity is added a CDU at a time, with rack units for single racks and row units as the hall grows. The facility water and electrical supply are the expensive parts to retrofit, so we size those for where you are going rather than where you are starting.
Do you install and maintain CDUs in Australia?
Yes. UPS Solutions designs, supplies, installs and commissions the CDU and the loop around it, then supports it with preventive maintenance, coolant and filtration service, leak checks and 24/7 emergency response across Australia, New Zealand and the Pacific.