Square D QO vs Homeline Panel Selection Reference

Why this matters

Square D (Schneider Electric) ships two residential breaker lines into U.S. distribution: QO and Homeline. They look similar on the shelf, mount in similar enclosures, and both carry UL 489 listing. They are not interchangeable. Installing a QO breaker in a Homeline panel (or the reverse) creates a non-listed assembly that fails inspection and voids the panel listing under NEC 110.3(B). Beyond the brand-mixing trap, the choice between QO and Homeline drives breaker availability for AFCI/GFCI/DF, the trip curve characteristics, and the panelboard's interrupting rating. Knowing the right answer at quote time prevents a re-quote when the customer's load list pulls in a CAFCI for a bedroom circuit and the only stock is the wrong line.

Mounting geometry

• QO: 3/4 inch wide single-pole breaker, plug-on or bolt-on depending on the panel
• Homeline: 1 inch wide single-pole breaker, plug-on only
• The mounting tab geometry differs; you cannot force a QO into a Homeline bus without bending the tab
• Both lines support tandem (half-size) breakers in panels that have CTL-marked positions

A QO panel of a given amp rating fits more circuits in the same enclosure depth than a Homeline panel of the same amperage; this is the historical reason QO is preferred in jurisdictions with crowded service panels.

Interrupting rating

• QO: 10 kAIC standard, 22 kAIC available on QOB and select QO bolt-on, 65 kAIC on QOB-VH versions
• Homeline: 10 kAIC standard across the entire line; no 22 kAIC option

For a residential service where the available fault current at the panel exceeds 10 kA (urban infill on a large pad-mount transformer with a short service drop), the QO family is where Square D's higher-interrupting residential options live and Homeline is not; Homeline tops out at the standard 10 kAIC. Do not read that as "any QO breaker is 22 kAIC," because it is not. Interrupting rating is a property of the specific catalog number and it is printed on the breaker. Pull the kAIC off the device and off the panel label, and confirm both cover the available fault current on the utility's letter.

NEC 110.9 requires equipment intended to interrupt current at fault levels to have an interrupting rating sufficient for the available fault current. Use the utility's available fault current letter to size; do not assume.

AFCI, GFCI, and DF availability

Both lines offer AFCI, GFCI, and Dual Function (DF) breakers, but with key differences:

• QO CAFCI (combination AFCI): single-pole 15 and 20 A, plus a 2-pole version for a multiwire branch circuit
• QO Dual Function (CAFCI + GFCI in one breaker): single-pole 15 and 20 A
• Homeline CAFCI and Homeline Dual Function: same single-pole 15 and 20 A coverage

Size the AFCI at the conductor's ampacity, not at whatever 2-pole AFCI the counter hands you. NEC 210.12 reaches 15 and 20 A, 120 V branch circuits, so a 2-pole AFCI for an MWBC is a 15 or a 20, and a 30 A "AFCI" is not a device this requirement has any use for.

NEC 2023 Section 210.12 requires CAFCI on all 120 V, 15 and 20 A branch circuits in dwelling kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas. NEC 2023 Section 210.8 requires GFCI on most outdoor, garage, basement, kitchen counter, bathroom, and laundry receptacles.

Dual function breakers handle both requirements on bedroom-laundry adjacency where a single circuit covers both areas.

Compatible panel families

QO breakers fit:

• QO panelboards (typical 100, 150, 200, 225 A residential)
• QOB bolt-on commercial panelboards
• NQOD and NQ I-Line industrial panels (with QO breaker accessories)

Homeline breakers fit:

• HOM panelboards only (100, 150, 200 A residential)

Do not mix. The bus design is incompatible despite physical similarity.

Generator interlock and load center compatibility

Both QO and Homeline panels accept generator interlock kits matched to the main breaker handle. The interlock kit ships per panel model:

• QO 200 A residential main: Square D PK3GTAQO or third-party listed equivalent
• Homeline 200 A: HOM-INTERLOCK or third-party listed equivalent

NEC 702.5 covers optional standby system requirements; the interlock prevents simultaneous utility-generator connection without a transfer switch.

Surge protection (Type 1 / Type 2)

NEC 2023 Section 230.67 requires surge protective devices (SPDs) on all new and replaced services for one- and two-family dwellings. Both QO and Homeline panels accept Type 2 SPDs in dedicated breaker slots or in the panel cover:

Two form factors, and the trade-off is slots against cover work:

• Breaker-style SPD (the QO and Homeline SurgeBreaker devices) lands in the bus like a 2-pole breaker. Simple install, costs you two slots.
• Cover-mount / external SPD (the Square D HEPD family and equivalents) mounts on or beside the enclosure and costs no slots, but needs a knockout and a short, straight lead run.

Keep the SPD's leads as short and as straight as you can get them in either case. Lead length and sharp bends add impedance the surge has to cross, and that shows up directly as a higher let-through voltage at the equipment you were trying to protect. Order the SPD by the current catalog number for the panel family in front of you.

When QO is the correct call

• Service has available fault current near or above 10 kA per utility letter
• Local AHJ requires bolt-on connections (some institutional and high-vibration installs)
• Customer plans large additions in the future and panel space matters
• The replacement parts inventory at the supply house is QO-heavy in your service area
• Critical loads where CAFCI/DF/GFCI series-rated combinations are required and the QO catalog covers more of the combinations

When Homeline is the correct call

• New residential service, 200 A or under, 10 kA available fault current sufficient per utility
• Cost-driven new construction with no special-application requirements
• Customer's existing service is already Homeline and matching reduces breaker inventory at the home
• Standard CAFCI/GFCI requirements that the Homeline catalog fully satisfies

Common errors to avoid

• Installing a QO breaker labeled "QO" into a Homeline panel because the breaker physically wedges in. The bus geometry differs and the listing is void.
• Buying Homeline panels for service upgrades on urban services that already exceed 10 kA available fault.
• Specifying a 2-pole Homeline DF breaker for a shared neutral circuit assuming it operates like a multi-wire branch circuit AFCI; both QO and Homeline DF breakers in 2-pole form factor must be used with appropriate neutral handling per NEC 210.4.
• Substituting non-Square D breakers (Connecticut Electric, Eaton CL) in Homeline or QO panels. NEC 110.3(B) requires equipment to be used per the listing; classified breakers are conditionally listed for specific panel families only.

References

• NEC 2023 Article 110 Requirements for Electrical Installations, Sections 110.3(B) Installation and Use, 110.9 Interrupting Rating
• NEC 2023 Article 210 Branch Circuits, Sections 210.8 and 210.12
• UL Standard 489 Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures
• Schneider Electric Square D Digest 178 (current revision) Product Catalog
• NEC 2023 Section 230.67 Surge Protective Device