A Square D branch-breaker catalog number starts with a product-line prefix, then identifies the pole count and ampere rating. Some families add an interrupting-rating suffix or a feature suffix. Reading those segments in the correct order is useful, but a plausible code is not enough. The full number must also agree with a published ampere ladder and interrupting-rating row.
The Breaker Part Number Finder works in both directions. It assembles a candidate from the selected QO, QOB, or Homeline parameters, then decodes the candidate through the same audited data before showing it. If the tables do not support the full combination, the result is needs-source instead of a guessed catalog number.
1. How a Square D branch-breaker number is built
The basic sequence is prefix, pole digit, ampere digits, optional rating suffix, optional feature suffix. The prefix identifies the product line and mounting family. The pole digit identifies how many poles the device opens. The ampere digits identify the rated current. A rating suffix can select a different interrupting family, while a feature suffix can identify a protection or packaging variation.
The reliable workflow is assemble, then decode. Start only with segments supported by the ordering grammar. Decode the complete candidate and compare the decoded line, poles, amperage, voltage, interrupting rating, and suffix meanings with the requested values. Suppress the number if the round trip does not agree.
2. Published amperage ladder by line and pole count
The finder uses the discrete standard sets below. An amperage outside the listed set is not rounded up and is not inserted into a catalog number.
| Line | Poles | Standard amperages |
|---|---|---|
| QO | 1 | 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70 A |
| QO | 2 | 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200 A |
| QO | 3 | 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100 A |
| QOB | 1 | 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70 A |
| QOB | 2 | 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125 A |
| QOB | 3 | 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100 A |
| Homeline | 1 | 15, 20, 25, 30, 35, 40, 45, 50 A |
| Homeline | 2 | 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200 A |
3. Interrupting-rating families in the sourced data
Interrupting rating is a safety value. It is read from the published Schneider matrix on the full catalog number. It is never inferred from one letter. The available fault current at the panel is determined by the utility and the service, not by this finder.
| Family or suffix | Interrupting rating | Scope note |
|---|---|---|
| Standard QO | 10 kA | Plug-on QO rows within the sourced pole and ampere bands |
| Standard QOB | 10 kA | Bolt-on QOB rows within the sourced pole and ampere bands |
| Standard Homeline | 10 kA | One-pole and two-pole Homeline rows in the sourced data |
| VH | 22 kA | High-interrupt QO and QOB bands |
| QOH | 42 kA | Identification only. The finder does not build this family. |
| QH and QHB | 65 kA | Identification only. The finder does not build these families. |
| H on a two-pole QO | 10 kA | 240 Vac common-trip device, not the high-interrupt family |
4. H, VH, QOH, and QH do not mean the same thing
These similar labels describe different families. A trailing H on a two-pole QO identifies a 240 Vac common-trip device that remains rated 10 kA. The VH suffix identifies the 22 kA family. QOH identifies the 42 kA family. QH and QHB identify 65 kA families.
Do not read the letter H by itself as a high-interrupt claim. Use the full number and the published interrupting matrix. QOH, QH, and QHB are included here so an existing label can be identified. The current finder does not build catalog numbers for those families.
5. Where the finder stops
Needs-source means the requested combination is not supported by a complete row in the packet data. The grammar may recognize a prefix or suffix while the required pole, ampere, voltage, or interrupting-rating row is missing. In that case the finder prints no candidate.
A guessed breaker catalog number is worse than no answer. It can look credible while carrying the wrong mounting family, interrupting rating, voltage basis, or feature. Resolve a needs-source result with the current manufacturer digest or a product page that enumerates the exact combination.
6. Panel listing controls the installation
Physically identical does not mean listed for the panel. The panelboard label identifies the breaker catalog numbers tested and listed for that panel. A breaker from another line or another manufacturer can fit the bus mechanically without being acceptable for that panel.
Check the label inside the panel door. Compare the full proposed catalog number with the listed numbers. If it is not on the label, ask the manufacturer or the authority having jurisdiction. This lookup does not determine panel compatibility, series rating, selective coordination, or NEC and AHJ acceptability.
7. Worked example: Homeline 1-pole 20 A
For Homeline, one pole, and 20 A, the verified catalog row is HOM120. The HOM prefix identifies Homeline. The 1 identifies the pole count. The 20 identifies the ampere rating. The sourced row lists 120/240 Vac and 10 kA AIR.
This example is individually enumerated in the packet data. It still does not prove that the breaker is listed for a particular panel. Confirm the full number on the panelboard label and in the current Schneider digest before ordering.
8. Sources
- Square D QO and QOB Miniature Circuit Breakers Catalog (Table 1 Interrupting Ratings) + Digest QO/Homeline catalog page. Document number: 0730CT9801R1/08. Revision: 07/2008 (Class 730); cross-checked vs 2020 Digest page + se.com, pin Digest 178 page/table before launch. Clause or table: Table 1: Interrupting Ratings (p5); Table 1.1 (QO) / Table 1.36 (HOM). Captured on 2026-06-27.
- Homeline source carried by the packet: USESI brochure 660697, Table 1.36.
- Current Schneider Electric Digest Plus QO table: QO220 and QO220H are enumerated separately; QO220H is in the 2-pole 240 Vac common-trip column at 10 k AIR.
- Current Schneider product records: QO220, QO220VH, and HOM120.
- Schneider Electric FAQ FA120545: QO and Homeline branch breakers are limited to their matching load-center lines.
- Schneider Electric FAQ FA174503: accepted QO load-center breaker families; last modified 2026-02-26.
- Schneider Electric FAQ FA109246: Square D manufacturer and listing boundary for QO and Homeline load centers; last modified 2026-04-17.
The current digest and physical product label control the final order.