NVIDIA Vera Rubin Cooling: Why 45°C Warm Water Means No Chillers Needed
- Tony Grayson
- Jan 9
- 9 min read
Updated: Jan 11
By Tony Grayson, President & GM of Northstar Enterprise + Defense | Former U.S. Navy Nuclear Submarine Commander | Stockdale Award Recipient | Veterans Chair, Infrastructure Masons
Published: January 9, 2026 | Updated: January 11, 2026 | Verified: January 11, 2026
TL;DR
NVIDIA Vera Rubin Cooling: 45°C doesn't kill cooling. It just kills the default chiller plant (read: you don't have to make it mandatory). NVIDIA Vera Rubin supports 45°C coolant, which is above ambient in most climates. That eliminates chillers. The physics flip: silicon junctions throttle at around 100°C, so 45°C water provides enough Delta-T. Architecture shifts from refrigeration to plumbing. The losers are chiller startups and single-loop RDHx vendors. The winners are CDU makers (the 'Super-Plumbers'), chemistry companies, and heat reuse integrators. The venture capital that chased 'better cold' should now chase 'better flow.'
In 30 Seconds
The Shift: Jensen Huang at CES 2026 said, 'With 45 degrees C, no water chillers are necessary. We are cooling this supercomputer with hot water.'
The Physics: Q = ṁ · Cp · ΔT. Delta-T is the 'cheapest knob to turn.' Larger ΔT (45°C supply, 65°C return) means lower pump power.
The Architecture: Three loops. FWS is the outdoor loop. CDU is the heart of the system. TCS is the chip loop. Redundancy shifts from chiller trains to pump strings.
The Reality: 'Chillerless' still needs trim chillers for the worst hours. Adiabatic assist introduces Legionella risk. 60°C return water is a burn hazard.
Commander's Intent
Purpose: Explain why 45°C cooling is a regime change, not an incremental improvement, and what operators must do differently.
Key Tasks: First, understand the physics flip. Second, architect three-loop warm-water systems. Third, shift the redundancy focus from chillers to plumbing. Fourth, master water chemistry.
End State: Readers understand why the era of the 'Meat Locker' data center is ending and what replaces it.
Buried in the details of the NVIDIA Vera Rubin launch was a number that likely made mechanical engineers cry: 45°C (113°F). To the layman, that sounds like a minor spec detail. To a data center infrastructure veteran, and especially to someone who spent years managing reactor thermal margins on a nuclear submarine, it is a regime change.
"45°C doesn't kill cooling. It just kills the default chiller plant. The new bottlenecks are ΔT, flow, controls, and water chemistry. The era of the 'Meat Locker' data center is ending. Time to burn those sweatshirts and invest in good steel-toed flip-flops."
Tony Grayson, Former Submarine Commander & Data Center Executive
The Physics of 45°C: The 'Warm Water' Shift because of NVIDIA Vera Rubin Cooling
For decades, most data centers removed IT heat by cooling the air. With Vera Rubin's direct-to-chip architecture supporting coolant supply temperatures up to 45°C, the physics flip completely.
The Chip: Silicon junctions throttle at around 100°C. With 45°C water entering the cold plate, you still have roughly 55°C of Delta-T to remove heat. That is a lot of margin.
The Facility: In many climates, 45°C is above ambient for most hours of the year. That means dry coolers can reject heat directly to outdoor air without mechanical refrigeration. When you operate above 45°C, you can go 'chillerless' in temperate zones for most operating hours.
The Math: I learned this formula in nuclear power school: Q = ṁ · Cp · ΔT. Heat removed equals mass flow rate times specific heat times temperature difference. ΔT is 'the cheapest knob to turn.' A larger ΔT (45°C supply, 65°C return) means lower flow rates, smaller pipes, fewer pumps, and less pump power.
"If you just spent hundreds of millions of dollars building a capex-heavy chilled-water plant, I have bad news. NVIDIA just made your cooling infrastructure a stranded asset for next-gen AI workloads. Your grandchildren will inherit a very expensive ice maker."
Tony Grayson
The Architecture Shift: From Refrigeration to Plumbing
In a warm-water DLC data center, you typically have three loops:
First, the FWS (Facility Water System). This is the 'dirty' outdoor loop. It includes the dry cooler, optional adiabatic assist for hot days, and an optional trim chiller for worst-case hours.
Second, the CDU (Coolant Distribution Unit). This is the 'heart' of the system. It isolates, filters, and exchanges heat between the FWS and TCS. Think of it as the boundary between the outdoor world and the clean chip loop.
Third, the TCS (Technology Cooling System). This is the 'clean' chip loop. It delivers ASHRAE W45 water to cold plates at the required flow rate and quality. It connects directly to the compute.
Redundancy shifts from chiller trains to pump strings, manifold isolation, and quick disconnects. The CDU becomes the new 'single point of failure' that everyone obsesses over.
The Reality Check: It's Not All Sunshine for NVIDIA Vera Rubin Cooling
Before you tear out all your chillers, know the risks for NVIDIA Vera Rubin Cooling:
Approach Penalty. Dry coolers still need some margin between ambient and supply. When ambient approaches 45°C (Phoenix in July), you need adiabatic assist or trim chillers. 'Chillerless' really means 'mostly chillerless.'
Bio-Growth Factor. Adiabatic systems introduce water mist, which introduces Legionella risk. You need ASHRAE 188 compliance, water treatment programs, and testing protocols. This is not optional.
Burn Risk. Water at 60°C can cause second-degree burns in seconds. Your maintenance procedures, lockout/tagout protocols, and hose ratings all need to be updated.
"Water chemistry, filtration, thermal management. These were life-or-death on a submarine. The same physics apply to high-density cooling loops. Hire an ELT from the Navy. They understand dissolved oxygen limits, micron ratings, and why biological growth in your cooling loop is an existential threat."
Tony Grayson
The Innovation Trap: Winners and Losers
The Losers:
'Better IT Chiller' Startups. If your pitch deck says 'better chiller for AI data centers,' you are now solving a shrinking problem. The market just moved away from you.
Single-Loop RDHx Vendors. Designs optimized for W17/W27 (cold water) need to be reconsidered. Material ratings, gasket specs, and control logic all change at W45.
The Winners:
The 'Super-Plumbers.' CDUs, manifolds, and quick disconnects that reliably handle massive flow rates. Capital reallocates from compressors to hydraulic precision.
The Chemistry Companies. Warm loops increase the risk of particulates, microchannel clogging, corrosion, and biological growth. Filtration and degassing become primary sources of uptime loss.
Heat Reuse Integrators. Heat reuse isn't blocked by temperature. It's blocked by commercial structure: off-take agreements, piping capex, and liability risk.
The Next Domino: High-Voltage DC
Cooling is only half the standardization wave. NVIDIA is moving toward 800 VDC reference architectures to scale racks from around 100 kW to 1MW or more while reducing copper losses and distribution complexity. The EV and solar industries have already adopted 800 VDC for similar benefits.
The Takeaway
The winners in 2026 aren't the ones with the smartest refrigeration physics. They're the ones who master the plumbing. The venture capital that used to chase 'better cold' should now be chasing 'better flow': reliability, leak risk, filtration, and standardized manifolds. The future isn't just hot. It's a high-pressure plumbing challenge.
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Frequently Asked Questions:
What does Tony Grayson say about 45°C data center cooling?
Tony Grayson, former nuclear submarine commander and data center executive (Oracle SVP, AWS, Meta), says: "45°C doesn't kill cooling. It just kills the default chiller plant. The new bottlenecks are ΔT, flow, controls, and water chemistry. The era of the Meat Locker data center is ending. The winners in 2026 aren't the ones with the smartest refrigeration physics. They're the ones who master the plumbing."
What is the TL;DR of the 45°C data center cooling revolution?
Tony Grayson explains: NVIDIA Vera Rubin supports 45°C coolant, which is above ambient in most climates. That eliminates chillers. Silicon junctions throttle at around 100°C, so 45°C water provides enough Delta-T. Architecture shifts from refrigeration to plumbing: CDUs, manifolds, pump strings, water chemistry. The losers are chiller startups and single-loop RDHx. The winners are CDU makers, chemistry companies, and heat reuse integrators.
Why does 45°C water eliminate the need for chillers in data centers?
Tony Grayson explains the physics: Silicon junctions throttle at around 100°C. With 45°C water entering the cold plate, you still have enough Delta-T (temperature difference) to remove heat efficiently. In many climates, 45°C is above ambient for most of the year. That means dry coolers can reject heat directly to outdoor air without mechanical refrigeration. Tony Grayson notes this is a 'regime change' from refrigeration to plumbing.
What is the warm water DLC architecture for AI data centers?
Tony Grayson describes three loops. First is the FWS (Facility Water System), the outdoor loop with dry cooler, optional adiabatic assist, and optional trim chiller. Second is the CDU (Coolant Distribution Unit), which is the 'heart' that isolates, filters, and exchanges heat between FWS and TCS. Third is the TCS (Technology Cooling System), the clean chip loop delivering ASHRAE W45 water to cold plates. Tony Grayson emphasizes that redundancy shifts from chiller trains to pump strings.
What is ASHRAE W45 and why does it matter?
Tony Grayson explains that ASHRAE TC 9.9 defines liquid cooling classes: W17, W27, W32, W40, W45, and W+. W45 means inlet water up to 45°C (113°F). NVIDIA Vera Rubin's W45 capability enables chillerless operation because dry coolers can handle heat rejection in most climates. Tony Grayson notes this shifts capital from compressors to hydraulic precision and flow management.
What is Q = ṁ · Cp · ΔT and why does it matter for data center cooling?
Tony Grayson (nuclear-trained) explains that this formula governs cooling efficiency. Q is heat removed, ṁ is mass flow rate, Cp is specific heat, and ΔT is temperature difference. Tony Grayson calls ΔT 'the cheapest knob to turn.' Example: 100 kW at ΔT = 20 °C requires approximately 19 gpm. Reduce ΔT to 10°C; the flow doubles. Larger ΔT (45°C supply, 65°C return) yields lower pump power, a key efficiency gain.
What are the risks of 'chillerless' 45°C data center cooling?
Tony Grayson identifies key risks. First is the approach penalty: dry coolers need a margin when the ambient temperature approaches 45°C, so trim chillers are still needed for the worst hours. Second is bio-growth: adiabatic assist introduces Legionella risks requiring ASHRAE 188 compliance. Third is winterization, which means preventing overcooling and thermal shock. Fourth is burn risk: 60°C return water is a safety hazard that requires updated hose specifications and lockout/tagout procedures.
What should data center operators ask for in RFPs after the 45°C shift?
Tony Grayson says stop asking for 'chiller tonnage.' New RFP requirements include TCS Inlet Class (ASHRAE W45 capability), Delta-T and pressure drop specs, SOO with CDU isolation behavior, isolation zoning with time-to-isolate targets, CDU redundancy strategy (N+1), filtration and chemistry specs, WUE/water plan for adiabatic usage, and material ratings at 60-65°C, including gasket creep plans.
Who are the winners and losers in the 45°C data center cooling shift?
Tony Grayson identifies the losers: 'Better IT Chiller' startups solving a shrinking problem, and single-loop RDHx designed for W17/W27. The winners are the 'Super-Plumbers' building CDUs, manifolds, and quick disconnects for massive flow rates. Also winning are chemistry companies handling filtration, degassing, and corrosion control, plus heat reuse integrators. Tony Grayson says: 'The venture capital that chased better cold should now chase better flow.'
What is 800 VDC, and why is it the next domino after 45°C cooling?
Tony Grayson explains that cooling is only half the standardization wave. The other half is electrical. NVIDIA is moving toward 800 VDC reference architectures to scale racks from around 100 kW to 1MW or more while reducing copper losses and distribution complexity. Tony Grayson notes the EV and solar industries have already adopted 800 VDC for similar benefits.
What did Jensen Huang say about Vera Rubin cooling at CES 2026?
Tony Grayson analyzed Jensen Huang's CES 2026 announcement: "The water that goes into it is 45 degrees C. With 45 degrees C, no water chillers are necessary for data centers. We are basically cooling this supercomputer with hot water." Tony Grayson notes that cooling stocks (Vertiv, Johnson Controls, Trane) dropped immediately. The market understood this is a regime change.
How does nuclear submarine experience apply to data center cooling?
Tony Grayson draws on nuclear submarine command: "Water chemistry, filtration, thermal management. These were life-or-death on a submarine. The same physics apply to high-density cooling loops. Hire an ELT (Electronics Laboratory Technician) from the Navy. They understand dissolved oxygen limits, micron ratings, and why biological growth in your cooling loop is an existential threat."
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Tony Grayson is a recognized Top 10 Data Center Influencer, a successful entrepreneur, and the President & General Manager of Northstar Enterprise + Defense.
A former U.S. Navy Submarine Commander and recipient of the prestigious VADM Stockdale Award, Tony Grayson is a leading authority on the convergence of nuclear energy, AI infrastructure, and national defense. His nuclear engineering background provides unique insight into thermal management, water chemistry, and the physics of reliability.
Tony Grayson led global infrastructure strategy as a Senior Vice President for AWS, Meta, and Oracle before founding and selling a top-10 modular data center company. Tony Grayson serves as Veterans Chair for Infrastructure Masons.
Read more at: tonygraysonvet.com