.png)
What a data center single line diagram shows
A single line diagram (SLD) is the one-page map of how power flows through a facility — from the utility connection and the generators, through transformers, transfer switching and UPS, down to the distribution boards that feed the racks. In a data center it is also the document that proves redundancy: it shows which paths can fail, and what keeps the load running when they do.
The mechanical single line diagram does the same for cooling: chillers, pumps, the hydronic loop and the terminal units that deliver cooling to the white space.
The problem with hand-drawn SLDs
SLDs are usually drawn after the sizing is finished, in a separate drawing tool. Every upstream change — a different IT load, an extra block, a new redundancy target — means redrawing by hand, and the diagram, the equipment schedule and the cost estimate gradually stop agreeing. Breaker ratings and cable sizes are often the first details to drift.
How DCtoB builds your single line diagrams
- Electrical SLD, utility to rack. Transformers, generators, ATS transfer, UPS and distribution panels are drawn automatically from the sizing — including parallel UPS modules and the redundant feeds to each row.
- Mechanical SLD. Chillers, pumps, CDUs and CRAHs appear on one clean, coordinated cooling schematic.
- Editable, and exportable. Both diagrams can be adjusted, and export to PDF, PNG and CSV.
- Schedules from the same source. Panel schedules list every board's incomers and outgoing ways with their breaker ratings; cable schedules size each run with voltage-drop and derating checks.
- Tested, not just drawn. The electrical diagram doubles as a live redundancy test — trip a UPS, a generator or a feeder and watch the load re-route. How the redundancy test works.
.png)
Getting breaker and cable sizing right at concept stage
Concept-stage schedules are where small sizing conventions decide whether the numbers hold up later. Two that DCtoB applies consistently:
- The continuous-load factor. Data center feeders carry their load for hours at a time, so in NEC-based practice the protective device for a continuous load is sized at 125% of that load. DCtoB applies the factor once, at the breaker, and sizes the cable to the breaker — so the margin is not counted twice.
- Parallel UPS incomers. A distribution board fed by a set of parallel UPS modules has one incomer per module, each sized to its own module — not a single main breaker sized to the whole set. The schedule states the number of incomers explicitly.
Transformer, generator, UPS and distribution sizing follow IEC/IEEE conventions for ratings and protection. See the standards DCtoB aligns with, and how the same design flows into the bill of quantities.