Template · Commercial and industrial

Parking lot lighting with contactor single line diagram

A lighting contactor under a photocell and a time clock switches a site lighting panel. Use this for parking lot or site lighting switched by a contactor under a photocell and a time clock, with a Hand-Off-Auto selector for testing.

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Parking lot lighting with contactor. 13 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 contactor rating against the feeder it switches, where its control power comes from, that the neutral is not switched, the continuous load on each circuit, the conductor size against voltage drop, and the equipment ground to every pole.

What the drawing shows

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

Symbol	Label	Rating or detail	Conductors feeding it
From (continues off sheet)	From panel HP-1	480Y/277V 3φ 4W
Circuit breaker	30A 3P	Site lighting
Contactor	Lighting contactor	30A · 3-pole · electrically held, 277V coil · NEMA 3R	4 #10 Cu + #10 G
Device	H-O-A selector (HOA)	Hand · Off · Auto
Device	Time clock (TC)	Astronomic
Device	Photocell (PC)	Dusk to dawn
Panel	Site lighting panel LS	60A MLO · 480Y/277V 3φ 4W
Circuit breaker	20A 1P	Phase A
Lighting	Pole lights, row 1	6 × 300W LED · 277V	2 #10 Cu + #10 G, 1" PVC underground
Circuit breaker	20A 1P	Phase B
Lighting	Pole lights, row 2	6 × 300W LED · 277V	2 #10 Cu + #10 G, 1" PVC underground
Circuit breaker	20A 1P	Phase C
Lighting	Pole lights, row 3	6 × 300W LED · 277V	2 #10 Cu + #10 G, 1" PVC underground

Notes on the sheet

The contactor is in the feeder and switches the whole site lighting panel. The neutral is not switched.
Control: the photocell and the time clock are in series, so the lights come on at dusk and go off at the hour set. Hand bypasses both, for testing and relamping. The 277V control circuit is taken from the line side of the contactor and fused.
Lighting is a continuous load: each circuit carries no more than 80% of its breaker (NEC 210.19(A) and 210.20(A)). Here each row is 6 × 300W ÷ 277V = 6.5A. With one row on each phase the feeder carries 6.5A a phase; × 125% = 8.1A. The 30A feeder and contactor leave room for more rows.
Branch conductors #10 Cu for voltage drop over the length of the run. An equipment grounding conductor to every pole; a ground rod at a pole is supplementary only (NEC 250.54).
Burial depth per NEC Table 300.5 (CEC Table 53) for the wiring method used.

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.