Preparing an Electrical Riser / Single Line Diagram for Permit

The single line diagram is the one drawing the electrical inspector reads first. A complete SLD moves the permit; an incomplete one stalls it.

What the SLD represents

A single line diagram shows the whole power distribution on one line per circuit — from the utility connection through metering, main protection, transformers, feeders, and every panelboard, ending at the load groups. It is a schematic, not a scaled layout.

Required content for permit

• Service entrance: utility source, voltage, phase, service capacity, metering, service conductor size and conduit.
• Main protection: main breaker or fused switch rating, AIC, enclosure type.
• Transformer(s): kVA, primary/secondary voltage, impedance, vector group, primary and secondary protection.
• Feeders: each feeder’s conductor size, quantity, conduit size, length, and breaker rating — usually in a feeder schedule table on the same sheet.
• Panelboards: designation, bus rating, main breaker, number of poles, voltage.
• Grounding: grounding electrode system, GEC size, ground rod detail.
• Load summary: connected load, demand factors, demand load, and the resulting service size — the calculation that justifies everything else.

Symbols and conventions

Use standard symbols (circle-with-diagonal for the utility transformer, rectangle for breakers with the trip rating noted, etc.). Label every device with its rating. Show phase and wire count (e.g. 3Φ, 4W) on each feeder.

Common rejection reasons

• Load summary missing or not matching the panel schedules
• Feeder sizes shown without conduit sizes
• No AIC ratings on protective devices
• Grounding electrode conductor not sized