Square D QO Generator Interlock Kit & Inlet Wiring Guide
Connecting a 240V portable generator inlet (NEMA 14-50, L14-30, 14-30, or 6-50) to a Square D QO load center requires a mechanical interlock plate matched to the main breaker layout (QORBGK2C), a listed QO 2-pole backfeed breaker, and a mechanical breaker hold-down retainer per NEC 408.36(D).
By Gil Sapir, Editor
Fast Answer⚡ Interlock Reference: Square D QO Load Centers▼
Mechanical Interlock Kit (QORBGK2C) + QO Backfeed Breaker
30A or 50A Double-Pole QO Breaker • 6 AWG THHN Cu (50A Inlet) or 10 AWG Cu (30A Inlet)
Compatible Generator Inlet Configurations for Square D QO
Comparison of NEMA 14-50, 14-30, 6-50, and L14-30 generator inlets when wired to a Square D QO load center.
| Generator Inlet | Max Breaker / Amps | Continuous Load (80%) | Max Running Watts | Copper Wire Gauge | Pin Configuration |
|---|---|---|---|---|---|
| NEMA 14-50 (240V) | 50A 2-Pole (QO) | 40A | 12,000 W peak | 6 AWG Cu (THHN) | 4-wire RV/Generator Inlet |
| NEMA 14-30 (240V) | 30A 2-Pole (QO) | 24A | 7,200 W peak | 10 AWG Cu (THHN) | 4-wire Dryer/Generator Inlet |
| NEMA 6-50 (240V) | 50A 2-Pole (QO) | 40A | 12,000 W peak | 6 AWG Cu (THHN) | 3-wire Welder/Generator Inlet |
| NEMA L14-30 (240V) | 30A 2-Pole (QO) | 24A | 7,200 W peak | 10 AWG Cu (THHN) | 4-wire Twist-Lock Generator Inlet |
Square D QO Load Center Configurations & Interlock Reference Matrix
All 10 Square D QO panel variants, main bus ratings, branch breaker types, and interlock kit references.
| Panel Configuration | Main Rating | Branch Breaker Type | Interlock Reference Model |
|---|---|---|---|
| Square D QO 200A Main Breaker | 200A | Type QO | QORBGK2C |
| Square D QO 100A Main Breaker | 100A | Type QO | QOCGK2C |
| Square D QO 125A Main Breaker | 125A | Type QO | QOCGK2C |
| Square D QO 150A Main Breaker | 150A | Type QO | QOCGK2C |
| Square D QO 200A Main Breaker | 200A | Type QO | QORBGK2C |
| Square D QO 225A Main Breaker | 225A | Type QO | QORBGK2C |
| Square D QOB Commercial 225A Panel | 225A | Type QOB | QOBGK3C |
| Square D QO 100A Outdoor NEMA 3R | 100A | Type QO | QOCGK2C |
| Square D QO 200A Plug-On Neutral | 200A | Type QO | QORBGK2C |
| Square D QO 42-Space 200A Panel | 200A | Type QO | QORBGK2C |
Generator NEMA 14-50 Inlet → Square D QO 200A Main Breaker Panel Wiring
Required Hardware Checklist for Square D QO
🔧 Mechanical Interlock Kit (QORBGK2C)
Matched to Square D QO main-to-branch breaker spacing. Physically prevents turning on the generator backfeed breaker while the main utility breaker is closed.
Check Retailer Availability on Amazon🔌 Outdoor Generator Power Inlet Box (30A / 50A)
NEMA 3R weatherproof generator inlet box (NEMA 14-50 / CS6365 for 50A or NEMA L14-30 for 30A) wired to a listed 2-pole QO backfeed breaker with hold-down kit.
Check Inlet Box Availability on AmazonRequired Wiring & Installation Accessories
50A Double-Pole Circuit Breaker
UL-Listed, mandatory for continuous EV charging load under NEC code.
6 AWG THHN Copper Wire (50ft Spool)
Heat-resistant 90°C copper conductor for conduit installation.
Hubbell HBL9450A / Bryant Electric 50A Industrial NEMA 14-50 Outlet
Industrial Grade heavy-duty receptacle (Hubbell HBL9450A / Bryant 50A). Mandatory safety upgrade to prevent melting on high continuous EV loads.
3/4" Schedule 40 PVC Conduit (10ft Lengths)
UV-resistant protection for exposed indoor/outdoor wire runs.
Generator Interlock Guides for Other Panel Lines
View NEC Article 702 interlock compatibility across other residential load center series:
Interlock Compatibility FAQ: Square D QO
Is a mechanical generator interlock kit compliant with NEC code for Square D QO panels?
Yes. Per NEC Article 702.5, a listed mechanical interlock plate physically prevents both the main utility breaker and the generator backfeed breaker from being turned on simultaneously in a Square D QO load center, and NEC 408.36(D) requires a mechanical hold-down retainer on the backfed plug-on breaker.
What size wire and breaker are required for a 50A or 30A generator inlet on a Square D QO panel?
A 50A generator inlet (NEMA 14-50 or CS6365) requires a 50A double-pole QO-type breaker with 6 AWG THHN copper wire in conduit (or 6/3 NM-B where permitted). A 30A generator inlet (NEMA L14-30 or 14-30) requires a 30A double-pole QO-type breaker with 10 AWG copper wire.
Which Square D QO panel ratings are covered on this page?
This guide covers all 10 residential Square D QO configurations, including QO 200A Main Breaker, QO 100A Main Breaker, QO 125A Main Breaker, QO 150A Main Breaker, QO 200A Main Breaker, QO 225A Main Breaker, QOB Commercial 225A Panel, QO 100A Outdoor NEMA 3R, QO 200A Plug-On Neutral, QO 42-Space 200A Panel, using QO branch breakers and reference interlock kit QORBGK2C.