The Siemens Q120 is a 20-amp single-pole Type QP plug-in circuit breaker for Siemens residential load centers — the most common replacement breaker for adding or swapping a 20-amp branch circuit in any Siemens, Murray, or compatible panel. The QP designation means it plugs directly onto the bus bar without tools or screws, snapping into place and making a solid electrical connection in seconds. Thermal-magnetic trip mechanism provides two-level protection: the thermal element trips on sustained overloads to protect wiring from heat damage, while the magnetic element trips instantly on short circuits to prevent arc damage. Rated at 10,000 AIC (amperes interrupting capacity) — the standard rating for residential service where available fault current rarely exceeds 10 kA. The toggle handle gives a clear mid-position indication when the breaker has tripped, so there is no guesswork when walking a panel. Fits Siemens ES, EQ, PL, P, W, G, HW, and other Siemens residential panel series.
What panels is the Siemens Q120 compatible with?
The Q120 fits all Siemens residential load center series including ES, EQ, PL, E, P, W, HW, HPW, G, HG, SGF, SN, XG, and OG panels. It also fits Murray panels, which Siemens acquired in 2002. The Type QP designation on the panel label confirms Q-series compatibility. Do not install a Q-series breaker in a Square D QO or Homeline panel, as the bus bar geometry is different — only use breakers that match your panel's listed type.
What is the difference between a 15-amp Q115 and a 20-amp Q120, and how do I know which one to use?
The amperage rating must match the wire gauge on the circuit. A 20-amp Q120 is for circuits wired with 12 AWG wire and protects loads up to 20 amps — standard for kitchen countertop outlets, bathroom outlets, garage circuits, and laundry. A 15-amp Q115 is for 14 AWG wiring and standard lighting and general outlet circuits. Installing a 20-amp breaker on 14 AWG wiring is a code violation and a fire hazard — the wire can overheat before the breaker trips.
How do I reset the Q120 after it trips?
When the Q120 trips, the toggle handle moves to a mid-position between ON and OFF. To reset: first turn the handle fully to OFF (you will feel it click), then turn it firmly back to ON. If it trips again immediately, there is an active fault on the circuit — do not force reset. Find and correct the overload or short before resetting.
Can I replace a breaker in my panel myself, or do I need an electrician?
Replacing an individual branch circuit breaker is a task many homeowners and DIYers complete safely, but it requires turning off the main breaker and working near the still-energized utility service wires at the top of the panel — those wires stay live even with the main breaker off. If you are comfortable identifying the correct breaker slot and working in the panel, it is legal in most jurisdictions with a permit. If you are unsure, hire a licensed electrician. Always confirm your panel type before ordering a replacement breaker.
What does the 10 kAIC interrupt rating mean?
The 10 kAIC (10,000 amperes interrupting capacity) rating means the Q120 can safely interrupt a fault current up to 10,000 amps without catastrophic failure — catching the arc internally rather than letting it escape. Most residential services from the utility are limited to fault currents well under 10 kA at the panel, so 10 kAIC is the standard rating for home breakers. High-fault commercial installations use higher AIC breakers (22 kA or 65 kA), but those are not needed in typical single-family residential service.
# Siemens 20 Amp Single Pole Type QP Circuit Breaker (Q120) **Model:** `Q120` **Brand:** Siemens **Category:** Circuit Breaker > The Siemens Q120 is a 20-amp single-pole Type QP plug-in circuit breaker for Siemens residential load centers — the most common replacement breaker for adding or swapping a 20-amp branch circuit in any Siemens, Murray, or compatible panel. The QP designation means it plugs directly onto the bus bar without tools or screws, snapping into place and making a solid electrical connection in seconds. Thermal-magnetic trip mechanism provides two-level protection: the thermal element trips on sustained overloads to protect wiring from heat damage, while the magnetic element trips instantly on short circuits to prevent arc damage. Rated at 10,000 AIC (amperes interrupting capacity) — the standard rating for residential service where available fault current rarely exceeds 10 kA. The toggle handle gives a clear mid-position indication when the breaker has tripped, so there is no guesswork when walking a panel. Fits Siemens ES, EQ, PL, P, W, G, HW, and other Siemens residential panel series. ## Specifications | Attribute | Value | |---|---| | Product Type | Circuit Breaker | | Poles | 1 | | Amperage | 20 | | Voltage Vac | 120 | | Interrupt Rating Ka | 10 | | Trip Type | Thermal-Magnetic | | Afci Protection | No | | Gfci Protection | No | | Self Test | No | | Plug On Neutral | No | | Wire Gauge Awg | 14-10 | | Compatible Panels | Siemens ES, EQ, PL, E, P, W, HW, HPW, G, HG, SGF, SN, XG, OG series; Murray panels | | Certifications | UL 489 | | Warranty | Lifetime Limited | ## What's Included - (1) Siemens Q120 Circuit Breaker Source: https://www.jaspecs.com/siemens/circuit-breaker/q120-siemens-20a-single-pole-circuit-breaker/