SPEC SHEET
Atlas DC1 — Canonical Specifications
v1.0 · single source of truth · cited by all 32 sections
When a Power Atlas section quotes a number for Atlas DC1, that number comes from this page. If you find a contradiction between this page and a section, this page wins.
⚡
AI/HPC Density Note — Atlas DC1 spec assumes traditional rack density
Atlas DC1 is spec'd at
~ 12 kW per rack (104 racks per row × 12 kW = 1.25 MW per row). This is appropriate for traditional enterprise + cloud workloads. Modern AI/GPU workloads (training NVIDIA H100/H200 clusters, custom AI accelerators) push rack densities to
30-100+ kW per rack. At those densities, Atlas DC1's air-cooled architecture is inadequate. AI deployments require:
- Liquid cooling (rear-door heat exchangers minimum, direct liquid cooling preferred) — see §35 Liquid Cooling
- Rack-level power 30-100+ kW (vs Atlas DC1's ~ 12 kW) — requires busway down each row instead of branch circuits
- Sub-millisecond network fabric (NVLink, InfiniBand) — fundamentally different cabling architecture
- Power density 300-1000+ kW per row (vs Atlas DC1's 1.25 MW per row)
Atlas DC1 is intentionally a representative TRADITIONAL DC. For AI/HPC, see
§36 AI/HPC Data Center Design.
Facility Profile
| Parameter | Value | Source / rationale |
|---|
| Type | Multi-tenant colocation data center | Reference scale — small enough to hold in head, large enough to span every concept |
| IT design load | 2.5 MW critical (2.632 MVA at PF 0.95) | "Critical load" = sum of UPS-fed IT power |
| Total facility design load (peak) | ~ 5.0 MW peak / ~ 4.5 MW continuous demand | IT 2.5 MW + mech ~ 1.8 MW + BOP 0.2 MW |
| Topology | 2N (per Uptime Tier III equivalent) | Two completely independent paths, each carries full IT load |
| Footprint | 200 ft × 300 ft × 25 ft tall | ~ 60,000 sq ft total |
| IT halls | 2 (Row A + Row B), 1.25 MW each | Symmetric layout, one row per side |
| Average rack density | ~ 12 kW per rack (104 racks per row) | Mix of standard servers + GPU-dense nodes |
| Climate zone | ASHRAE Zone 4A (mixed-humid, e.g., Northern Virginia) | Affects mech sizing + ASHRAE 90.4 compliance |
| Year built | 2026 (current NEC = 2023; ASHRAE 90.1-2022) | Sets code basis |
Electrical — Sources & Distribution
| Equipment | Spec | Per Side |
|---|
| Utility service | 12.47 kV, 3φ, 60 Hz, primary metered, two independent feeders | One feeder per side (true 2N at utility level) |
| Available fault current at PCC | 50 kA RMS symmetric at 12.47 kV (X/R ≈ 8.5) | — |
| Service transformers | 2 × 2,500 kVA pad-mount, 12.47 kV–480Y/277V, %Z = 5.75, Δ-Y grounded | 1 per side · TX-A and TX-B |
| Standby generators | 2 × 2,500 kW (3,125 kVA at 0.8 PF) Tier 4 final diesel | 1 per side · GEN-A and GEN-B |
| ATS | 2 × 4,000 A bypass-isolation, open-transition | 1 per side · ATS-A and ATS-B |
| 480V switchgear | 2 × 4,000 A buses, 65 kA AIC, GFP per NEC 230.95 | 1 per side · 480V SWGR-A and SWGR-B (cross-tie normally open) |
| UPS | 4 × 1,250 kVA online double-conversion, 5-min ride-through | 2 per side · UPS-A1 + UPS-A2; UPS-B1 + UPS-B2 |
| UPS battery | VRLA 540V strings (270 cells × 2V), 300 Ah cells, 2 strings per UPS for N+1 | 2,160 cells total facility |
| PDUs | 500 kVA, 480V → 415Y/240V, K-13 isolation transformer + integral panel | Multiple per side (typical 4-6 per row) |
| RPPs | 415Y/240V, 400A bus, 42-circuit panelboards | One per row of racks |
| Rack PDU strips | 415Y/240V or 240V split-phase, dual-fed (A + B) | 2 per rack (one from A, one from B path) |
Electrical — Mechanical Loads (Side A; Side B is identical)
| Equipment | Quantity per side | Each (HP / kW) | FLA at 480V | Notes |
|---|
| Centrifugal chillers (CH-1, CH-2 on Side A) | 2 + 1 standby across both sides (3 + 1 N+1) | 450 HP / 337 kW each | 480 A (per NEC 430.250) | VFD-driven; CH-1 + CH-2 on Side A; CH-3 + CH-4 on Side B |
| Condenser water pumps | 2 | 75 HP / 56 kW each | 96 A | VFD-driven, one per chiller |
| CRAH fans (Computer Room Air Handlers) | 4 | 50 HP / 37 kW each | 65 A | VFD-driven, modulating with cooling demand |
| Cooling tower fans | 2 | 30 HP / 22 kW each | 40 A | VFD-driven |
| Make-up water + glycol pumps | 2 | 5 HP / 4 kW each | 7.6 A | — |
| Mech room lighting + receps | — | 15 kVA | 18 A | — |
| IT hall lighting + lifesafety | — | 22 kVA | 27 A | — |
Side A — Load Study (Canonical)
This is the official load study for Side A. Use these numbers when sections cite Atlas DC1 Side A.
| Load | Connected (kW) | Demand factor | Demand (kW) | NEC mult | Sized (kW) |
|---|
| UPS-A1 + A2 input (1.25 MW IT × 1/ηUPS×0.96) | 1,302 | 1.0 | 1,302 | 1.25 (continuous, NEC 215.3) | 1,628 |
| Chillers CH-1 + CH-2 (2 × 337 kW) | 674 | 1.0 (peak) | 674 | NEC 430.24: 1.25 × largest + others | 758 |
| Pumps CWP-1 + CWP-2 (2 × 56 kW) | 112 | 1.0 | 112 | 1.0 (other motors per 430.24) | 112 |
| CRAH fans (4 × 37 kW) | 149 | 0.95 (modulating) | 142 | 1.0 | 142 |
| Cooling tower fans (2 × 22) | 44 | 0.7 (cycling) | 31 | 1.0 | 31 |
| Lighting (mech + IT halls) | 22 | 1.0 | 22 | 1.25 (continuous) | 28 |
| Receptacles & misc | 15 | 0.5 (NEC 220.44 above 10 kVA) | 9 | 1.0 | 9 |
| TOTAL — Side A | 2,318 | — | 2,292 | — | 2,708 kW |
Apparent power: 2,708 / 0.95 PF = 2,851 kVA. Current at 480V: 3,430 A. Both sides sum to ~5,700 kVA total facility.
Sizing Reconciliation
| Item | Required (Side A) | Spec'd | Margin | Notes |
|---|
| 480V SWGR-A bus | 3,430 A | 4,000 A | +17% | Allows future load growth |
| TX-A capacity | 2,851 kVA | 2,500 kVA | −12% | Marginal. Real Atlas would step up to 3,000 kVA, OR accept overload during peak IT + mech coincidence (rare) |
| GEN-A capacity | 3,000 kVA (with motor starting margin) | 3,125 kVA (2500 kW × 1/0.8) | +4% | Tight. Real Atlas would size 3,000 kW (3,750 kVA) for comfort |
| UPS-A1 + A2 combined | 1,316 kVA at full IT | 2,500 kVA (2 × 1250) | +90% | 2 × 1250 needed because each must carry full IT load alone (N+1 within Side A) |
Fault Current Profile
| Bus | Available fault current (sym RMS) | Equipment AIC required |
|---|
| 12.47 kV utility (PCC) | 50 kA | 50 kA MV switchgear |
| 12.47 kV MV SWGR bus | 50 kA (utility-limited) | 50 kA |
| 480V SWGR-A bus | 50.3 kA (per §12 calc — utility + TX-A combined) | 65 kA (next std up) |
| UPS-A1 input (480V, after feeder) | ~ 35 kA | 35 kA |
| UPS-A1 output (480V) | UPS limits to ~ 3× rated = ~ 4,500 A | 22-35 kA (downstream OCPD) |
| PDU-A1 panel (480V) | ~ 25 kA | 25 kA |
| PDU-A1 secondary (415V) | ~ 18 kA (after K-13 isolation xfmr) | 22 kA |
| RPP-A1-1 (415V) | ~ 12 kA | 14 kA |
| Rack PDU strip | ~ 5 kA | 10 kA (panelboard standard) |
Arc Flash Profile (Illustrative)
These numbers are illustrative for handbook purposes — real values come from running IEEE 1584-2018 with site-specific inputs (electrode configuration, exact gap, working distance, box dimensions).
| Bus | Trip path (clearing time) | Incident energy @ 18" | PPE Cat |
|---|
| 12.47 kV MV SWGR | Utility 51, ~ 200 ms | ~ 3 cal/cm² | 1 |
| 480V SWGR-A (with 87B bus diff) | 87B trip, 4 cycles (~ 67 ms) | ~ 6 cal/cm² | 2 |
| 480V SWGR-A (without 87B) | Upstream 51 backup, ~ 200 ms | ~ 18 cal/cm² | 3 |
| UPS-A1 distribution | UPS output CB ~ 500 ms | ~ 12 cal/cm² | 3 |
| PDU-A1 panel (480V) | UPS output CB ~ 500 ms | ~ 8 cal/cm² | 2 |
| PDU-A1 panel (415V) | PDU primary CB ~ 200 ms | ~ 4 cal/cm² | 1-2 |
| RPP-A1-1 (415V) | PDU sub-CB ~ 100 ms | ~ 2 cal/cm² | 1 |
| Rack PDU branch | RPP branch CB ~ 50 ms | ~ 0.5 cal/cm² | 0 |
Cooling System
| Item | Spec |
|---|
| IT heat load | 2.5 MW = 711 tons of cooling required |
| Installed chiller capacity | 4 × 750 tons = 3,000 tons (3 + 1 N+1) |
| Operating chillers (max) | 3 (one always in standby for N+1) |
| Chiller load factor | ~ 32% (711 / 2,250) — large headroom for facility cooling + humidity |
| Cooling architecture | Water-cooled centrifugal + cooling tower + CRAH air handling |
| Supply air temp | 72°F at server inlet (per ASHRAE TC 9.9 recommended) |
Standby + Emergency Systems
| System | Spec |
|---|
| NEC classification | NEC 702 (optional standby) — IT load is not life safety |
| Life safety (NEC 700) | Egress lighting, fire alarm, sprinkler controls — fed from dedicated NEC 700 ATS not shown on main SLD |
| Generator paralleling | NONE — each gen is dedicated to its side. Open-transition ATS only. |
| UPS ride-through | 5 minutes at full load (battery sized to last well past genset start) |
| Genset start time | 10 seconds to rated voltage + frequency |
| ATS transfer time (open-transition) | ~ 200 ms outage on transfer |
| Net IT load impact | Zero — UPS rides through entire 10-sec genset start + 200-ms transfer |
| Genset fuel | 24-hour sub-base tank per genset, plus on-site 96-hour bulk tank |
Grounding
| Item | Spec |
|---|
| System grounding scheme | Solidly grounded throughout |
| Each TX as separately derived system | Yes (NEC 250.30) — own MBJ + GEC at each 480V SWGR |
| Each PDU as separately derived system | Yes (NEC 250.30) — K-13 isolation xfmr → fresh 415Y/240V grounding at PDU |
| Grounding electrode system | Concrete-encased electrode (CEE/Ufer) + ground ring (250 ft 4/0 bare Cu) + building steel |
| GEC size | 2/0 Cu (per NEC 250.66) |
| GFP at service | NEC 230.95 — 1,200 A pickup, 0.3 sec delay, performance-tested per 230.95(C) |
| IT signal reference grid | Per ANSI/TIA-942, separate grid bonded to building EGC at single point |
Power Quality + Compliance
| Metric | Atlas DC1 | Limit / target |
|---|
| PUE (Power Usage Effectiveness) | 1.40 (typical 2N redundancy) | < 1.5 (modern); < 1.3 (hyperscale) |
| TDD at PCC (12.47 kV) | ~ 4% (after 12-pulse VFD upgrade) | 5% per IEEE 519 (SCR ≈ 17 → 5%) |
| Power factor at PCC | ≥ 0.95 | 0.90 utility threshold (no PFC caps — server PSUs handle this) |
| Voltage flicker | None significant (no large DOL motors; all VFD) | IEEE 1453 Pst < 1 |
| ASHRAE 90.1 LPD compliance | 0.39 W/sf in IT hall, 0.43 mech, 0.59 office | All within limits |
| ASHRAE 90.4 (DC energy) | MLC 0.20, ELC 0.16 | Within climate zone limits |
Lightning + Surge Protection
| System | Spec |
|---|
| NFPA 780 LPS | Class I — 90 air terminals @ 20 ft spacing, 18 down conductors (2/0 Cu, 60 ft spacing), bonded to ground ring |
| SPD at MV switchgear | 15 kV class surge arrester, 12 kV MCOV, 10 kA discharge |
| SPD at 480V SWGR | Type 1 hardwired ahead of main, 200 kA per phase, VPR 1500V |
| SPD at distribution panels | Type 2, 120 kA, VPR 1200V |
| SPD at UPS input + output | Type 2, 80/40 kA, VPR 1000/800V |
| SPD at rack PDU | Type 3 integral, 10 kA, VPR 600V |
Battery Room (Class I Div 2 Group B)
| Item | Spec |
|---|
| Classification | Class I Div 2 Group B (hydrogen evolution from VRLA charging) |
| Total battery cells facility-wide | 2,160 (4 UPS × 2 strings × 270 cells) |
| Rooms | 4 dedicated battery rooms (one per UPS), separate from UPS room |
| Ventilation | 500 cfm each room, continuous fan + H2 sensor backup |
| H2 alarm thresholds | 1% (25% LEL) — alarm; 2% — emergency vent |
| Equipment in room | Class I Div 2 rated lighting + monitoring; non-sparking fan |
| Spill containment | Not required for VRLA (sealed); would be for flooded |
PV + Energy Storage
| System | Spec |
|---|
| PV array | 200 kW DC rooftop (480 modules × 420 W), 4× 50 kW string inverters with module-level rapid shutdown |
| PV interconnection | Supply-side connection (NEC 705.11) at 480V SWGR-A — bypasses 120% rule |
| ESS | 500 kWh / 250 kW Li-ion (LFP) for peak shaving + ride-through augmentation |
| ESS room | NFPA 855 compliant — sprinklers, gas detection, ventilation, max 50 kWh per cabinet, 3 ft separation |
EV Charging
| Equipment | Qty | Spec |
|---|
| Level 2 EVSE (staff parking) | 4 | 208V 1φ, 40 A continuous, NEMA 14-50 + J1772 |
| DC Fast Charger (fleet) | 1 | 480V 3φ, 75 kW, CCS Combo + NACS |
| EVEMS | — | Coordinated 75 kW peak (vs 140 kW unmanaged) — sheds L2 during DCFC session |
Single-Line Diagram
The full one-line diagram appears in §02 How Design Starts. The hero summary appears on the landing page.
Where Atlas DC1 Appears
Every section in Power Atlas uses Atlas DC1 as its primary worked example. See Connection Map for cross-references.
Canonical Atlas DC1 specifications · v1.0 · 2026-05-04
If a section number disagrees with this page, this page is correct.