Glossary

Data center procurement and delivery terms, acronyms included. Sections parallel the Knowledge Base hubs, grouped under the three parts — the vocabulary companion to the lessons. A living document: add terms as they come up, correct definitions that prove wrong in practice. Entries are alphabetical within each section.

Part I: The Domain

01 Power Systems 34 terms

A/B feeds: dual independent power paths to each rack.
ATS / STSAutomatic / Static Transfer Switch: switches load between sources; static is solid-state and faster.Taught in 01.20 The Power Chain, End to End
Behind the meter: generation on the customer's side of the utility meter — invisible to the grid. On-site gas turbines, BESS discharging to shave peaks.
BESSBattery Energy Storage System: utility-scale batteries for resilience, availability, or load management.
Busway / busduct: prefabricated overhead electrical distribution allowing tap-offs along its length.Taught in 01.20 The Power Chain, End to End
Capacity: the maximum power a system can deliver.
A nameplate rating, not a measurement of what is actually drawn.
Taught in 01.10 Power First: The Constraint That Rules Everything
DRUPSDiesel Rotary UPS: backup power combining a diesel engine with a kinetic (flywheel) energy store — no batteries. Lower footprint and maintenance than static UPS; different cost and service profile.Taught in 01.20 The Power Chain, End to End
Energization: the milestone when utility power goes live to the site.
Generator / genset: on-site backup generation, typically diesel at 2.5-3.3 MW per unit (70-100 weeks).70-100 weeksTaught in 01.20 The Power Chain, End to End
GWgigawatt: a unit of electric power equal to one billion watts.
The unit for the largest AI campuses and regional load planning.
See also kW, MWTaught in 01.10 Power First: The Constraint That Rules Everything
iPDUintelligent PDU: rack-level distribution with per-outlet metering and switching.Taught in 01.20 The Power Chain, End to End
IT MW: The amount of electrical power delivered directly to servers, storage drives, and networking gear inside the data hall.
It measures the actual productive power consumed by the computing hardware doing the work. It excludes facility overhead.
Also called Critical Load, Critical IT Load, IT Equipment EnergyTaught in 01.10 Power First: The Constraint That Rules Everything
kWkilowatt: a unit of electric power equal to one thousand watts.See also MW, GWTaught in 01.10 Power First: The Constraint That Rules Everything
Load: total amount of raw electrical power being drawn by a system
Moves with IT utilization; the quantity that matters operationally.
See also IT MW, Utility MWTaught in 01.10 Power First: The Constraint That Rules Everything
LV distribution: low-voltage switchgear and distribution boards spreading power from the transformers to the halls.Taught in 01.20 The Power Chain, End to End
MV / LVMedium / Low Voltage: the distribution voltage classes inside the facility.Taught in 01.20 The Power Chain, End to End
MWmegawatt: a unit of electric power equal to one million watts.
The unit for the largest AI campuses and regional load planning.
See also kW, GWTaught in 01.10 Power First: The Constraint That Rules Everything
N+1 / 2N: redundancy notation. N+1 is one spare module beyond need. 2N is two fully independent systems, each able to carry the full load.
Package: a separately procured scope of equipment. One link of the power chain with its own vendors, specification, and lead time.Taught in 01.20 The Power Chain, End to End
PDUPower Distribution Unit: distributes power to racks in the data hall.Taught in 01.20 The Power Chain, End to End
Power skid: prefabricated modular power package — switchgear, UPS, and distribution pre-assembled on a skid. 52-80 weeks.52-80 weeks
PUEPower Usage Effectiveness: a standard metric used to measure the energy efficiency of a data center.
Calculated by dividing the Utility MW by the IT MW
$\text{PUE} = \text{Utility MW} \div \text{IT MW}$ $\text{Utility MW} = \text{IT MW} \times \text{PUE}$
The overhead multiple of the compute load.
Ideal is 1.0, which means 100% of the utility power directly fuels the IT equipment (servers, storage, and networking). No real facility gets there.
Rule of thumb: 1.5 is average, under 1.3 is excellent, above 1.8 is legacy, 1.1-1.2 is hyperscale
See also IT MW, Utility MWTaught in 01.10 Power First: The Constraint That Rules Everything
RMURing Main Unit: compact MV switchgear distributing power in a ring topology.
RPPRemote Power Panel: panel distributing power to rows of racks.Taught in 01.20 The Power Chain, End to End
Single-line diagram: the electrical drawing that traces power from the utility feed to the racks through every device in the chain. Procurement reads it as the package list.Taught in 01.20 The Power Chain, End to End
SMRSmall Modular Reactor: factory-built nuclear reactor at a fraction of traditional scale. Discussed as future behind-the-meter power for data centers; not yet a procurable product at scale.
Substation: where high-voltage grid power is stepped down for the site. Substation transformers are the longest-lead package in the matrix (100-140 weeks).100-140 weeksTaught in 01.20 The Power Chain, End to End
Switchboard: a free-standing assembly of busbars, breakers, and switches that divides one large incoming feed into smaller outgoing circuits. The main distribution point at low voltage.Taught in 01.20 The Power Chain, End to End
Switchgear: the assembly of breakers and controls that distributes and protects power at MV or LV.Taught in 01.20 The Power Chain, End to End
Tie breaker: a breaker joining two bus sections or two switchboards. Closing it lets one side carry the other through a failure or a maintenance shutdown.Taught in 01.20 The Power Chain, End to End
Transformer: steps voltage up or down between stages of the power chain.Taught in 01.20 The Power Chain, End to End
UPSUninterruptible Power Supply: battery-backed power bridging utility failure to generator start; also conditions power. 52-70 weeks.52-70 weeksTaught in 01.20 The Power Chain, End to End
Utility feed: the grid connection. Power availability and the energization date set project feasibility.Taught in 01.20 The Power Chain, End to End
Utility MW: The total amount of raw electrical power drawn from the public power grid to run the entire data center campus, including cooling and support loads (lighting, security, office, losses).
Always larger than IT MW.
Also called Total Facility Energy, Grid CapacityTaught in 01.10 Power First: The Constraint That Rules Everything

02 Cooling and Mechanical 10 terms

Aisle containment: physical barriers separating hot and cold aisles to prevent mixing.
CDUCoolant Distribution Unit: pumps liquid coolant to racks in liquid-cooled designs.
Chiller: central plant producing chilled water. 45-65 weeks.45-65 weeks
Cooling tower / dry cooler: rejects heat from the chilled-water loop to atmosphere.
CRACComputer Room Air Conditioner: self-contained unit with its own refrigeration (DX) rather than chilled water.
CRAHComputer Room Air Handler: circulates hall air across a chilled-water coil. 35-50 weeks.35-50 weeks
Direct-to-chip / immersion: liquid cooling methods for high-density (AI) racks.
DXDirect Expansion: refrigeration-cycle cooling, like a large air conditioner.
Hot aisle / cold aisle: the standard airflow layout — racks draw from cold aisles, exhaust to hot aisles.
WUEWater Usage Effectiveness: water consumed per unit of IT energy. The water analogue of PUE.

03 Building and Delivery 29 terms

BMSBuilding Management System: controls and monitors mechanical and building systems.
Brownfield / adaptive reuse: building on previously developed land or converting existing structures.
CCTV: camera surveillance infrastructure.
Commissioning (Cx): the staged verification proving systems work as designed. Levels 1-5 run from documentation and component checks through startup, functional testing, and integrated systems testing.
Critical path: the longest chain of dependent activities. Any delay here delays the project.
Cross-connect: a physical fiber or copper connection between two parties in the facility.
DCIMData Center Infrastructure Management: the software layer for capacity and operations.
EPMSElectrical Power Monitoring System: monitors the power chain.
FAT / SATFactory / Site Acceptance Test: witnessed testing before shipment and after installation.
Fiber trunk: pre-terminated high-count fiber assemblies feeding the hall.
Float: schedule slack on non-critical activities.
Gaseous / clean-agent suppression: gas-based suppression for spaces where water is unacceptable.
GCGeneral Contractor: the prime contractor managing construction.
Greenfield: new construction on undeveloped land.
GSOCGlobal Security Operations Center: centralized security monitoring.
Load bank: resistive equipment simulating IT load during commissioning.
Mantrap: interlocked double-door entry for physical security.
MMRMeet-Me Room: the telecom room where carriers interconnect.
NTPNotice to Proceed: the owner's formal instruction to start work; usually the date the clock starts.
Pre-action sprinkler: requires two triggers (detection plus sprinkler head) before water releases — protects equipment from accidental discharge.
Punch list: outstanding items to complete before acceptance.
Rack / cabinet: the standardized server enclosure (19-inch, measured in RU).
Raised / access floor: elevated flooring creating a plenum for cabling and airflow.
RFSReady for Service: the endpoint — capacity the customer can actually use.
Site / shell / core: the delivery layers. Site is land, civil, and utilities. Shell is the building envelope. Core is the base power and cooling infrastructure. Tenant systems (TFO) come after.
Substantial completion: the contractual milestone when the work is usable for its purpose.
TFOTenant Fit Out: tenant-specific systems and data-hall work.
VESDAVery Early Smoke Detection Apparatus: aspirating smoke detection for data halls.
White space: the data hall itself — the finished area housing IT equipment.

04 Market and Commercial 14 terms

Build-to-suit (BTS): a facility designed and built for a single tenant.
Carrier-neutral: a facility where tenants can choose among multiple network providers.
Colo / colocation: leasing data center space and power from an operator. Wholesale is large blocks; retail is smaller footprints.
Dark fiber: unlit fiber leased for the tenant's own equipment.
Hyperscaler: a cloud operator building at massive scale (AWS, Azure, Google Cloud, Meta).
IXInternet Exchange: where networks interconnect and exchange traffic.
Neocloud: cloud provider built specifically for AI/GPU workloads (e.g., CoreWeave, Lambda, Crusoe).
NNN (triple-net) lease: the tenant pays rent plus taxes, insurance, and maintenance.
Powered land: land valued for available utility MW and delivery date rather than square footage.
Powered shell: a building delivered with power infrastructure but no tenant fit-out.
PPAPower Purchase Agreement: long-term contract to buy electricity (often renewable or nuclear) at agreed terms. Negotiated separately from facility rent.
SLAService Level Agreement: contracted uptime and performance commitments.
Tier I-IV: the Uptime Institute resilience classification, from basic single path to fault-tolerant.
Turnkey: fully finished, ready-to-occupy capacity.

Part II: The Craft

05 Sourcing and Vendor Management 11 terms

EXW / FOB / DDPIncoterms: define where cost and risk transfer between seller and buyer — at the factory gate (EXW), on board the vessel (FOB), or delivered duty-paid (DDP).
Framework agreement: umbrella purchasing terms with a vendor covering multiple future orders across projects. The European term for what the US calls an MSA.
LLELong-Lead Equipment: equipment whose factory lead time controls the schedule — transformers, generators, switchgear, UPS, chillers. The working schedule breaks LLE into specification, shop drawing review, PO prep, PO issued, manufacturing, delivery window.Taught in 10.00 Overview
POPurchase Order: the commercial instrument that commits the buy.
RFP / RFQ / RFIRequest for Proposal / Quotation / Information: the competitive solicitation stages, in increasing specificity.
Rigging: specialized moving and placement of heavy equipment.
Sole source: buying from one vendor without competition; needs documented justification.
Staging: holding equipment in a warehouse until the site is ready to receive it.
Submittal: the contractor's detailed documentation (shop drawings, product data) submitted for approval before fabrication. Submittal cycles sit on the critical path for LLE.
Vendor / supplier master: the system of record for approved vendors.
White-glove delivery: premium handling for sensitive equipment.

06 Cost and Value 4 terms

$/kW/month: the standard pricing unit for data center capacity.
Ramp: the schedule by which a tenant takes down contracted power over time.
Should-cost: an independent estimate of what something ought to cost, used to test bids.Taught in 06.00 Overview
TCOTotal Cost of Ownership: purchase price plus installation, energy, maintenance, and replacement over the asset's life.Taught in 06.00 Overview

07 Contracts and Risk 11 terms

CFCIContractor-Furnished, Contractor-Installed: the contractor buys and installs. Covers bulk materials (cabling, conduit, ductwork) and civil/structural work.Taught in 08.00 Overview
Change order: formal amendment to scope, price, or schedule after award.
Contract novation: transferring a contract and its obligations from one party to another — e.g., moving open equipment orders from an incumbent provider to the owner during transition.Taught in 10.00 Overview
Escalation clause: contract term adjusting price against material or labor indices when input costs move.
GMPGuaranteed Maximum Price: caps what the owner pays for a defined scope; savings below the cap are shared or returned per terms, overruns are the contractor's (subject to approved changes).
MSAMaster Services Agreement: umbrella terms with a vendor covering multiple future orders.
OFCIOwner-Furnished, Contractor-Installed: the owner buys and controls vendor selection, pricing, and delivery; the contractor receives, sets, and connects. In the procurement matrix this covers all major electrical and mechanical packages.Taught in 08.00 Overview, 10.00 Overview
OFOIOwner-Furnished, Owner-Installed: the owner buys and installs — usually IT hardware and systems the tenant or a specialist team controls.Taught in 08.00 Overview
O&MOperations and Maintenance: the ongoing running of the facility — staffing, maintenance, reliability KPIs — often contracted separately from construction.
SOWStatement of Work: defines what is being bought or built under an MSA or contract.
Warranty: the manufacturer's or contractor's guarantee to repair or replace defective work for a defined period. The warranty handoff — who holds it after installation — is a key OFCI term.

Part III: The Function

08 Operating Models 7 terms

Category management: organizing procurement by spend category, with an owner per category.Taught in 08.00 Overview
Center-led procurement: central strategy and standards, local execution.
Centralized procurement: one team buys everything across projects and sites.
Decentralized procurement: each project or site buys for itself.
DOADelegation of Authority: who can approve what spend. A core piece of any target operating model.Taught in 08.00 Overview
PMOProject Management Office: the function that standardizes project delivery.
RACIResponsible, Accountable, Consulted, Informed: the matrix assigning who does the work, who owns the decision, who weighs in, and who is told — for each decision.

09 Processes and Systems 6 terms

CLMContract Lifecycle Management: the system and process for drafting, approving, storing, and managing contracts.
P2PProcure-to-Pay: the end-to-end process from requisition through payment.
Spend analysis: what we buy, from whom, at what price. The baseline for sourcing decisions.
Tail spend: low-value, unmanaged purchases outside strategic sourcing. Automation and AI target it first — high volume, low judgment required.
Three-way match: the PO, the receipt, and the invoice agree before payment is released.
Vendor / supplier master: the system of record for approved vendors.

10 Transitions 3 terms

Decision gate: a go/no-go point between transition phases.
Knowledge transfer: moving pricing history, vendor relationships, and expediting know-how out of the incumbent team before exit.
Phased transition: moving work in stages with decision gates, not a single cutover.