Solution · AC40 / AC45 · Single-Phase Immersion

AC40 / AC45 — the inference block
of the AI Factory

Containerized single-phase immersion cooling delivering 400 kW of IT capacity across 8 immersion tanks — built for PCIe GPU fleets in 4U 8-GPU servers: RTX 4090 / 5090, RTX PRO 6000 Blackwell Server Edition, H100, H200. Up to 512 GPUs per container, factory pre-integrated, with free cooling down to PUE ≈ 1.05 in the right climate.

400 kW
IT Capacity
512 GPUs
PCIe · Max per Container
ΔT 8 K
Immersion Oil Loop
PUE ≈ 1.05
Free-Cooling Climates*
01
What AC40 / AC45 are

One container. Eight tanks. Zero fans on the GPUs.

You've seen the business case — modular blocks, fast monetization, inference-first economics. AC40 and AC45 are the Immersion Computing Units in that equation: a 40-ft or 45-ft container holding 8× A32 single-phase immersion tanks plus one 10 kW air-cooled rack. Servers sit fully submerged in dielectric fluid; each tank carries up to 50 kW with dual redundant CDUs, and all heat leaves the container on a warm-water loop at 32/37 °C. Everything is integrated and tested at the factory — on site you connect power, water, and network.

Form Factor
40-ft (AC40) · 45-ft (AC45) container
IT Capacity
360 kW rec. / 400 kW max · 8× A32 tanks + 1× 10 kW air rack
GPU Platform
4090 · 5090 · RTX PRO 6000 Blackwell SE · H100 · H200 (PCIe, 4U 8-GPU)
Cooling
Single-phase immersion · dual 2N CDU per tank
PUE
≈ 1.05–1.10 free-cooling zone · up to ≈ 1.20 hot climates*
Lead Time
~185–230 d from contract

IT Load vs. Facility Load. 400 kW is what the servers draw. Total facility load is ~440–500 kW once cooling and auxiliaries are added — the gap is set by PUE, which depends on your site's climate. *Sites whose historical peak dry-bulb stays ≤ 24 °C run on pure dry coolers (free cooling, lowest PUE); hotter sites add a hybrid chiller. Always confirm which figure an "X MW" requirement refers to.

02
Why Immersion Cooling

For PCIe inference fleets, immersion is the lowest-OpEx path to density.

🛢️

It cools everything, not just the chip

The whole server — GPUs, VRMs, NICs, DIMMs — is submerged in dielectric fluid. No cold plates to match to each SKU, no fans to fail, no hot spots. Up to 50 kW per 32RU tank, with both air-cooled servers retrofitted for immersion and immersion-ready designs supported.

🌡️

It runs warm, so it runs almost free

Oil enters the tank at ≤ 35 °C and leaves at ≈ 43 °C; the facility loop runs at 32/37 °C. Where the historical peak dry-bulb stays ≤ 24 °C, dry coolers alone reject all heat — no compressors, PUE as low as ≈ 1.05. Hotter sites add a hybrid chiller that trims only the peaks.

🔁

Redundancy is built into every tank

Each A32 tank carries dual CDUs in full 2N — two pumps, plate heat exchanger, and filtration per CDU, hot-swappable in minutes without draining the tank. A single pump or CDU failure never stops the servers.

03
Pick your container

Same 400 kW core. Two power architectures.

Both containers share the identical immersion core — 8× A32 tanks, the same oil loop, the same cooling rules. They differ in where the UPS lives.

AC40 AC45
Container 40-ft 45-ft (adds a dedicated power bay)
IT Capacity 360 kW rec. / 400 kW max 400 kW
UPS (EATON 9395XR-600, 600 kW) External — customer-supplied Built-in power bay
Battery Backup ~10 min (customer-supplied 2× 93LiG2) ~20 min (built-in 2× 93LiG2)
UL Compliance UL compliant
Best For Lowest cost & size; sites with existing UPS Turnkey & regulated markets

Redundancy model. The container is the smallest redundancy unit: tanks are 2N on cooling internally, a single container has no internal IT redundancy, and system-level N / N+1 / 2N is built by adding containers.

04
Go deeper

Inside the technical deep-dive

The full engineering model is live and interactive — every number computed from the same physics engine our design team uses, from tank-level oil flow to container PUE.

🛢️

Tank & container layout

Walk the 8-tank layout of AC40 and AC45, power bay included.

🐠

Immersion loop, animated

Watch the oil and water loops move through the dual-CDU tank diagram.

💧

Flow & thermal design

Oil flow per tank (≈ 11–12 m³/h), facility water, and the ΔT budget.

🧮

GPU capacity & PUE by site

Pick a PCIe server and a climate — get GPU count, binding constraint, and PUE band.

Ready to see the engineering?
Configuration is engineered by Fog — pricing goes through your account manager.