Project Deschutes: Data Center Facilities Specification, v0.8.0 (2 MW coolant distribution unit)

Overview

The specification gathers both the product requirements of a 2 MW CDU and its facility interface in one document. The CDU is a liquid-to-liquid heat exchanger between the secondary (IT) and primary (facility) loops, running DI water or PG25 with a 3 C approach target. Three dual-pass plate heat exchangers operate in parallel. The design mandates N+1 pumps, 44 micron front-serviceable filtration, about 3 GPM of 0.2 micron side-stream filtration, an air separator, a flow-through expansion tank, a three-zone leak rope and pH and conductivity telemetry. Wetted materials are stainless steel, copper and EPDM, and nickel-plated brass is prohibited on the secondary side.

Thermal and hydraulic ratings are tabulated: 2000 kW thermal load, 500 GPM IT flow, 500 GPM facility flow at 0.25 GPM/kW, 80-90 psi available IT-side pressure, 15-30 psi facility-side drop, 0-130 psig operating pressure and a relief valve at 130 psi. The heat exchanger performance table shows, for example, a 2.3 C approach at 545 GPM and 2150 kW. The pump delivers 500 GPM at 112 psi and 37 kW, is sealless, and each pump has its own VFD. The CDU measures 65 x 93.1 x 47.2 in and weighs 6910 lb wet and 5310 lb dry.

Electrical input is 380-416 VAC three-phase (operating range 90-110% of nominal), 47-63 Hz, with 100 A Class J/gG fusing on each line. VFD and PSU hold-up must follow the CBEMA curve, and voltage THD must stay under 8% and current THD under 20%. At least 1N feed redundancy is required and 2N is desired. For controls, the PLC supports both IPv4 and IPv6 and Modbus/TCP; the default pump control is fixed pressure differential and the default valve control is fixed approach temperature. The CDU must be controllable singly or as part of a group of parallel CDUs.

The second half of the document turns to the facility and validation. The Redmond interface defines hot aisle containment for racks 28 in wide and up to 50 in deep: a cold aisle of at least 54 in, a hot aisle of at least 68.4 in with RDHx, a 14 ft minimum ceiling height and eight 600 A busducts in the hot aisle. Validation chapters list component and assembly tests from water pipe kits and filters to heat exchangers. The document is v0.8, and it states itself that piping and controls detail will be added in later versions.

Key points

1. Ratings: 2000 kW thermal load, 3 C approach, 500 GPM IT flow, facility flow 0.25 GPM/kW (500 GPM), IT-side available dP 80-90 psi, facility dP 15-30 psi, operating pressure 0-130 psig, 74 kW power consumption.
2. CDU size 65 x 93.1 x 47.2 in (W x H x D); 6910 lb wet, 5310 lb dry; maximum packaged height 100 in.
3. Required features: N+1 pumps, 44 micron front-serviceable filtration, ~3 GPM 0.2 micron side-stream filter, air separator, flow-through expansion tank, 3-zone leak rope, 130 psi relief valve, pH and conductivity telemetry.
4. Wetted materials stainless steel, copper and EPDM; nickel-plated brass not allowed on the secondary side. Coolant: DI water or PG25, with approved chemical mixes (for example 95% DI water + 5% chemical).
5. Electrical: 380-416 VAC 3-phase (operating 90-110%), 47-63 Hz, 100 A Class J/gG fusing, VFD/PSU hold-up to CBEMA; voltage THD <8%, current THD <20% (IEEE 519); at least 1N, preferably 2N feeds.
6. Heat exchanger: three dual-pass units in parallel; example point 2.3 C approach at 545 GPM and 2150 kW.
7. Pump: 500 GPM at 112 psi, 37 kW, sealless, each with its own VFD; redundant components must be replaceable during operation.
8. Controls: IPv4 and IPv6, Modbus/TCP; default fixed pressure-differential pump control and fixed approach-temperature valve control.
9. Redmond interface: rack 28 in wide, max 50 in deep; cold aisle at least 54 in, hot aisle with RDHx at least 68.4 in, ceiling at least 14 ft, 8 x 600 A busducts.
10. IT rack power interface: IEC 60309 5-pin 30/32 A, 4 feeds in '4 makes 3'; RDHx 2397.78 mm high, 716 mm wide, 331.91 mm deep.

Using it in design

• Define a 2 MW CDU catalogue template for liquid-cooling layouts: dimensions, wet weight (6910 lb) for slab loading, 74 kW parasitic load, 3 C approach and 0.25 GPM/kW facility flow.
• Verify the 500 GPM facility-side flow and 15-30 psi dP budget in pipe sizing and pump selection; check the 0-130 psig limit and 130 psi relief valve against the secondary loop.
• Feed the CDU electrical loads (about 38 kVA VFD, roughly 64 A at minimum voltage) into harmonic/THD and ride-through checks, and verify that UPS and generator redundancy are at least equal to feed redundancy.
• Add the 4-feed '4 makes 3' pattern at 90 kW per rack position as a selectable distribution topology; include RDHx depth and the roughly 95 mm gap in row pitch.
• Reflect the Redmond aisle rules (54 in cold, 68.4 in hot with RDHx, 14 ft ceiling, 6 ft and 10 ft transport aisles) in layout checks, noting that structural and seismic qualification belongs to the facility owner.
• Add the secondary-side ban on nickel-plated brass to the coolant and material compatibility check.

Who should read it

Mechanical and electrical engineers designing liquid-cooled AI halls, CDU manufacturers and colocation operators.

Document contents

1. License
2. Compliance with OCP Tenets
3. Scope
4. CDU Physical Dimensions & Mechanical Data
5. Performance Specifications (Thermal/Hydraulic)
6. Coolant Specifications
7. Heat Exchanger Performance
8. Operational Modes
9. Functional Specifications
10. Electrical Specifications
11. Power - maintenance and hotswap requirements
12. Controls
13. VFD
14. Safety and Compliance
15. CAD, BOM, Tools for Assembly and Manufacturing
16. Maintenance/service
17. Documentation, Packaging and Shipping requirements
18. Barcode Label Specification for Liquid Cooling Systems & Components
19. Redmond: Hot Aisle Containment (HAC) Interface
20. General validation requirements
21. Component validation
22. Assembly validation

Related standards

• IEEE 519
• ITIC/CBEMA curve
• IEC 60309
• OCP Modular Technology Cooling System

Read the document

Publication details

Authors

Jorge Padilla; Madhu Iyengar; Vijay Soundararajan; Gaurav Soni; Scott McCauley

Publisher

Open Compute Project Foundation

Year

2025

Document number

v0.8.0

Document language

English

Source type

Industry body

Access

Open licence — downloadable

Licence

OWFa 0.9 — Open Compute open specification licence; redistribution permitted

Licence evidence

www.opencompute.org

Citation