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Commercial rooftop PV, string inverters single line diagram

DC combiners and two 50 kW inverters into an AC combiner panel, backfed at the switchboard.

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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Commercial rooftop PV, string inverters single line diagram: DC combiners and two 50 kW inverters into an AC combiner panel, backfed at the switchboard. — Commercial rooftop PV, string inverters. 17 devices on an 11 × 17 in sheet with a title block and notes column.

What the drawing shows

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

Symbol	Label	Rating or detail	Conductors feeding it
Utility source	Utility service	480Y/277V 3φ 4W
Current transformer	CT cabinet	Utility metering
Circuit breaker	600A 3P	Main
Panel	Main switchboard MSB	800A bus · 480Y/277V 3φ 4W
Circuit breaker	Branch breakers
To (continues off sheet)	To building loads
Circuit breaker	175A 3P	PV backfeed, opposite end from main
Disconnect switch	PV AC disconnect	200A · NEMA 3R, lockable	4 #2/0 Cu + #6 G, 2" EMT
Panel	PV AC combiner panel	400A MLO · 480Y/277V
Circuit breaker	80A 3P	INV-1
Inverter	String inverter 1	50 kW · 480V · 60.1A	4 #4 Cu + #8 G
PV combiner	DC combiner 1	8 strings · 20A fuses, 1000V DC · disconnect	2 #1/0 Cu PV + #6 G
PV array	PV array 1	144 × 450W · 64.8 kW	PV wire #10 Cu, 8 strings of 18
Circuit breaker	80A 3P	INV-2
Inverter	String inverter 2	50 kW · 480V · 60.1A	4 #4 Cu + #8 G
PV combiner	DC combiner 2	8 strings · 20A fuses, 1000V DC · disconnect	2 #1/0 Cu PV + #6 G
PV array	PV array 2	144 × 450W · 64.8 kW	PV wire #10 Cu, 8 strings of 18

Notes on the sheet

Each inverter: 50 kW ÷ (1.732 × 480V) = 60.1A; × 125% = 75.2A, protected at 80A. Both: 120.3A × 125% = 150.4A, protected at 175A.
Busbar check at MSB: 800A bus × 120% = 960A ≥ 600A main + 175A PV breaker. PV breaker at the opposite end of the bus from the main.
String fuses: module Isc 11.5A × 1.56 = 17.9A, so 20A. Combiner output: 8 × 17.9A = 143.5A, on 1/0 Cu.
Rapid shutdown per NEC 690.12 (CEC Rule 64-218).

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.