If you are specifying or replacing a type HOM breaker, you are working with Square D’s HOMeline series—a 1-inch-per-pole, plug-on molded case circuit breaker (MCCB) designed for 120/240V AC residential and light commercial load centers. Standard HOM breakers carry a 10 kA Ampere Interrupting Capacity (AIC) and are available from 15A to 150A. The governing rule for selection is simple: match the breaker’s thermal-magnetic time-current curve to your specific load type (resistive, inductive, or motor), and never exceed the panel’s bus bar stab rating.
Type HOM Breaker Specification & Rating Table
Before pulling a breaker off the shelf, you need to understand its electromechanical limits. The table below outlines the core specifications for the standard HOMeline lineup, including the internal trip mechanisms and accessory coil ratings used in advanced setups.
| Model Prefix | Pole Config | Ampacity & Contact Rating | Breaking Capacity (AIC) | Internal Trip Coil Type | Accessory Coil Voltage |
|---|---|---|---|---|---|
| HOM115 - HOM150 | 1-Pole | 15A - 50A @ 120V AC | 10 kA @ 120V | Thermal Bimetal + Magnetic Solenoid | N/A (No accessory space) |
| HOM215 - HOM2100 | 2-Pole | 15A - 100A @ 240V AC | 10 kA @ 240V | Thermal Bimetal + Magnetic Solenoid | 120V AC (HOM-ST Shunt Trip) |
| HOM2020 | Tandem (2x 1P) | 15A/20A @ 120V AC | 10 kA @ 120V | Thermal Bimetal + Magnetic Solenoid | N/A (CTL restricted) |
| HOM320 - HOM3100 | 3-Pole | 20A - 100A @ 240V AC | 10 kA @ 240V | Thermal Bimetal + Magnetic Solenoid | 120V AC / 24V DC (HOM-ST) |
Which Rating Column Governs Your Load?
When sizing a breaker, the Ampacity & Contact Rating column governs continuous load capacity (derated to 80% for continuous loads over 3 hours per NEC 210.20). However, the Breaking Capacity (AIC) governs fault safety. If your utility transformer can deliver 15,000 amps of fault current to your panel, a standard 10 kA HOM breaker will violently fail during a dead short. In high-fault scenarios, you must step up to a QO series or a specific high-AIC HOM variant. Finally, the Internal Trip Coil Type dictates how the breaker reacts to overloads versus dead shorts, which brings us to wiring and load matching.
Line vs. Load Wiring and Accessory Coil Protection
Understanding the physical and electromechanical wiring of a breaker requires separating the main current path (the contacts) from the trip mechanism (the coils).
Contact Side Wiring (Line and Load)
The main contacts inside a HOM breaker bridge the panel’s bus bar stab (Line) to the branch circuit wire (Load). While single-pole HOM breakers are technically non-directional for standard AC thermal-magnetic tripping, standard practice and NEC labeling requirements dictate that the bus stab is the LINE and the lug is the LOAD. For 2-pole and 3-pole breakers, the internal common trip bar mechanically links the contacts. If you backfeed a breaker (wiring the load side to the source) without a proper hold-down kit, you violate NEC 408.36 and risk the breaker ejecting from the bus during a fault.
Coil Side Wiring and DC Flyback Protection
If you are using a 2-pole or 3-pole HOM breaker equipped with a Shunt Trip accessory (model HOM-ST), you are wiring an external trip coil. The shunt trip coil is rated for specific voltages (e.g., 120V AC or 24V DC). When wiring a DC shunt trip coil—common in solar battery disconnects or BMS-controlled panels—you must install a flyback diode in parallel with the coil.
Selection Decision Path by Load Type
You cannot treat fuses and breakers as interchangeable, nor can you treat all breakers identically. A standard thermal-magnetic breaker operates on an inverse time-current curve. This means a 20A HOM breaker carrying a 200A short circuit will trip instantaneously (via the magnetic solenoid coil in <15 milliseconds), but a 26A overload (130%) will take roughly 30 to 60 seconds to trip the thermal bimetallic strip. Matching this curve to your load prevents nuisance tripping.
| Load Category | Examples | Required HOM Breaker Type | Why This Curve/Type Wins |
|---|---|---|---|
| Standard Resistive | Lighting, receptacles, baseboard heaters | Standard HOM (Thermal-Magnetic) | Inrush current is minimal. Standard inverse curve provides optimal wire protection. |
| High Inductive / HID | Fluorescent ballasts, large transformers, HID lighting | HOM with HID rating (or SWD for 120V fluorescent) | Handles the high inrush current and the severe inductive kickback voltage when the contacts open. |
| HVAC / Motor | AC compressors, well pumps, blower motors | HACR Type HOM | HACR (Heating, Air Conditioning, Refrigeration) breakers have a modified magnetic trip threshold to ignore the 6x-8x Locked Rotor Amps (LRA) inrush without nuisance tripping. |
| Non-Linear / SMPS | Server racks, LED drivers, VFDs | Standard HOM, but size at 125% of continuous draw | Harmonics cause excess heat in the thermal bimetallic element. Upsizing the breaker (and wire) prevents phantom thermal trips. |
For a concrete numeric example: A 3-ton AC compressor might have a Maximum Overcurrent Protection (MOCP) rating of 40A, but a Minimum Circuit Ampacity (MCA) of 24A. You must use a 40A HACR-rated type HOM breaker (HOM240) to survive the motor startup surge, but you must wire it with 8 AWG copper (rated for 40A in the 75°C column) to satisfy the MOCP, even though the running load is only 24A. Always consult the equipment nameplate over general NEC tables for motor circuits.
Testing Procedures and the "Replace vs. Repair" Rule
Breakers degrade over time. The thermal bimetallic strip can fatigue from repeated overloads, and the mechanical latch can accumulate dust or corrosion. Knowing how to test a breaker and when to discard it is critical for panel reliability.
How to Test a HOM Breaker Dead (De-energized)
- Continuity Check: With the breaker removed from the panel and switched to ON, place your multimeter probes on the line stab and the load lug. You should read less than 0.5 ohms. Switch it to OFF; it should read OL (Open Loop).
- Mechanical Toggle Test: The toggle should snap firmly into ON, OFF, and the center TRIPPED position. If the toggle feels "mushy" or fails to latch in the ON position, the internal spring mechanism is broken.
- Insulation Resistance (Megger): For high-value commercial panels, apply 500V DC between the line/load terminals and the breaker's plastic casing. It should read >100 MΩ. Lower readings indicate carbon tracking or moisture ingress inside the molded case.
How to Test a HOM Breaker Live (Energized)
- Voltage Drop: With the circuit under normal load, measure the AC voltage from the bus bar stab (just upstream of the breaker) to the load lug terminal on the breaker. A healthy breaker will drop less than 50 millivolts. A drop exceeding 200mV indicates pitted internal contacts or a loose lug connection generating dangerous heat.
- Thermal Imaging: Use an infrared thermometer or thermal camera. A breaker running 20°C hotter than adjacent breakers under similar loads is suffering from internal contact resistance or a degraded thermal element.
When to Repair vs. Replace
Unlike older open-frame air circuit breakers, the type HOM breaker is factory-sealed with rivets and ultrasonic welds. If a breaker fails to reset, trips prematurely, or shows thermal damage on the bus stab clip, replace it immediately. Attempting to pry open a HOM casing to clean contacts or adjust the bimetallic strip destroys the arc chute's geometry, guaranteeing a catastrophic failure the next time it attempts to interrupt a fault current. Replacement units cost between $8 and $45 depending on amperage; the risk of an electrical fire from a botched repair is incalculable.
By strictly matching the breaker’s time-current curve to your load, respecting the AIC rating of your panel, and verifying connections with live voltage-drop testing, you ensure your HOMeline panel operates safely and reliably for decades. For deeper code compliance regarding breaker grouping and handle ties, refer to NFPA 70 (NEC) Article 210 and 240.
