Template · Commercial and industrial

480Y/277V service with 208V transformer single line diagram

800A switchboard with a 75 kVA transformer for 120/208V loads. Use this for a commercial service at 480Y/277V: an 800A switchboard with a 75 kVA transformer for the 120/208V loads.

A free template with typical ratings, conductor callouts and general notes. Open it, change what differs on your job, fill in the title block and export a PDF.

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480Y/277V service with 208V transformer single line diagram: 800A switchboard with a 75 kVA transformer for 120/208V loads. — 480Y/277V service with 208V transformer. 15 devices on an 11 × 17 in sheet with a title block and notes column.

What the reviewer checks on this drawing

The reviewer checks the transformer and the bonding of its secondary, arc-flash and available fault current labels on the switchboard, and, where required, selective coordination reviewed by the engineer of record.

What the drawing shows

Every device on the sheet, in the order power reaches it.

Symbol	Label	Rating or detail
Utility source	Utility transformer	480Y/277V 3φ 4W
Current transformer	CT cabinet	Utility metering
Circuit breaker	800A 3P	Main
Panel	Main switchboard MSB	800A · 480Y/277V 3φ 4W
Circuit breaker	225A 3P	HP-1
Panelboard	Panel HP-1	277V lighting, HVAC
Circuit breaker	125A 3P	T-1 primary
Transformer	Transformer T-1	75 kVA, 480V Δ – 208Y/120V
Circuit breaker	225A 3P	Secondary main
Panelboard	Panel LP-1	225A · 208Y/120V
Circuit breaker	100A 3P	RTU-1
Disconnect switch	Disconnect	100A · NEMA 3R
Load	RTU-1	Rooftop unit
Circuit breaker	30A 3P	SPD
Device	Surge protective device (SPD)

Notes on the sheet

Transformer T-1: 90A primary, 208A secondary. Secondary bonded as a separately derived system.
Arc-flash and available fault current labels applied to the switchboard.
Selective coordination and arc energy reduction reviewed by the engineer of record where required.

Diagram is schematic and not to scale. Field-verify existing equipment ratings. Ratings and conductor sizes shown are typical. Confirm against the adopted code, the equipment listing and a load calculation before installation. Code references are to the 2023 NEC and the 2024 Canadian Electrical Code: see references and editions.