Siemens QDF Breaker AFCI and GFCI Protection

Siemens QDF dual-function breakers combine AFCI, GFCI, overload and short-circuit protection. Compare Q115DF, Q120DF and related models, ratings and neutral configurations.

Table Of Contents
  1. Siemens QDF Breakers
  2. QDF Dual Protection
  3. AFCI and GFCI
  4. QDF and QFGA2
  5. QDF Ratings
  6. Q115DF vs. Q120DF
  7. Neutral Connections
  8. Load-Center Compatibility
  9. Replace a QDF Breaker
  10. Select a Replacement
  11. Find QDF Breakers
  12. QDF Breaker Summary
  13. Siemens QDF Breaker FAQ
  14. Siemens QDF Breaker Glossary

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Siemens QDF Breakers

Siemens QDF Dual-Function AFCI and GFCI Protection

A Siemens QDF dual-function breaker gives you arc-fault, ground-fault, overload and short-circuit protection in one branch-circuit breaker. You’ll find them in residential or light-commercial load centers where a circuit needs AFCI and GFCI protection.

The QDF series like Q115DF and Q120DF and QFGA2 as the designation for these breakers. Let’s compare available models and how to select the correct breaker replacement.

QDF Dual Protection

What Is a Siemens QDF Dual-Function Breaker?

A Siemens QDF breaker combines three forms of circuit protection:

  • Thermal-magnetic protection for overloads and short circuits
  • Combination-type AFCI protection for hazardous arcing conditions
  • Class A GFCI protection for current leakage causing electrical-shock hazard

Standard thermal-magnetic breakers protect conductors from over-current, but they don’t always detect low-level ground leakage or hazardous arcing. A dual-function breaker adds those protective capabilities without requiring two separate devices.

Siemens identifies these as one-pole, 120-volt breakers available primarily in 15- and 20-amp designs. The company’s dual-function product information shows self-testing and LED trip indication in the family’s features. Siemens’ dual-function breaker literature shows family specifications.

AFCI and GFCI

How AFCI and GFCI Protection Work Together

Arc-fault and ground-fault protection address different electrical hazards.

A combination-type AFCI monitors the circuit for dangerous series and parallel arcing. Damaged insulation, loose connections and deteriorated cords are causes.

A Class A GFCI compares the current traveling through the ungrounded and grounded circuit conductors. It trips when the imbalance reaches the device’s ground-fault threshold. Siemens specifies 5 mA Class A GFCI protection for this breaker family.

Combining both functions can simplify a circuit needing protection against electrical fires and shock hazards. For more background on the difference between these conditions, see Relectric’s Ground Fault and Arc Fault 101 guide.

QDF and QFGA2

QDF and QFGA2 Naming Explained

The terminology can be confusing because QDF and QFGA2 describe related aspects of the same breaker family.

QDF is the suffix used in Siemens catalog numbers like Q115DF. Siemens’ catalog identifies the corresponding 10 kA plug-in breaker type as QFGA2.

Higher-interrupting versions use related type designations:

  • QFGA2 for standard 10 kA models
  • QFGAH2 for 22 kA models
  • HQFGA2 for 65 kA models
  • QFGA2N for 10 kA plug-on-neutral models

This means a breaker labeled Type QFGA2 can have Q115DF or Q120DF as the catalog number. When requesting a replacement, provide both markings whenever possible. Siemens’ circuit-breaker catalog confirms these catalog-number and type relationships. cache.industry.siemens.com

QDF Ratings

Siemens QDF Breaker Ratings and Catalog Numbers

The following table shows the principal plug-in QDF catalog-number patterns.

Siemens QDF breaker replacement help
Siemens catalog numberSiemens typePolesAmperageVoltageInterrupting ratingNeutral arrangement
Q115DFQFGA2115A120V10 kAPigtail
Q120DFQFGA2120A120V10 kAPigtail
Q115DFHQFGAH2115A120V22 kAPigtail
Q120DFHQFGAH2120A120V22 kAPigtail
Q115DFHHHQFGA2115A120V65 kAPigtail
Q120DFHHHQFGA2120A120V65 kAPigtail
Q115DFNQFGA2N115A120V10 kAPlug-on neutral
Q120DFNQFGA2N120A120V10 kAPlug-on neutral

Use this table for identification. Confirm the complete catalog number and load-center compatibility before ordering or installation.

Q115DF vs. Q120DF

Comparing Q115DF and Q120DF Breakers

The main difference between the standard Q115DF and Q120DF is amperage.

The Q115DF is a 15-amp, one-pole breaker for a 120-volt circuit. The Q120DF is a 20-amp, one-pole breaker with the same basic dual-function protection. Both standard models have a 10 kA interrupting rating.

You can’t upgrade from 15 to 20 amps just because the larger breaker fits the panel. The circuit conductors, connected equipment, receptacles and overall branch-circuit design must be right for 20 amps.

If you’re comparing QDF models with ordinary thermal-magnetic breakers, Relectric’s Siemens QP breaker guide explains the standard QP family. A standard QP breaker doesn’t replace the AFCI and GFCI functions supplied by a QDF model.

Neutral Connections

Pigtail Versus Plug-On-Neutral QDF Breakers

A Siemens AFCI GFCI breaker uses a neutral pigtail that connects to the load center’s neutral bar. The branch-circuit neutral connects to a terminal on the breaker.

Plug-on-neutral models (N suffix) in Q115DFN and Q120DFN, connect directly to a neutral rail. This can reduce wiring and help produce a cleaner installation.

A plug-on-neutral breaker needs a load center designed and labeled for the plug-on-neutral breaker type. A regular pigtail breaker is wired per instructions.

Don’t confuse either configuration with a Siemens QN main breaker. Despite similar letters, QN breakers are for higher-amperage main or feeder applications; QDF breakers protect individual branch circuits.

Load-Center Compatibility

Checking Siemens Load-Center Compatibility

A breaker that attaches to the bus isn’t always approved for the panel. Before selecting a Siemens QDF breaker replacement, locate the load-center label and wiring diagram. Record:

  • Complete load-center catalog number
  • Permitted breaker types
  • System voltage
  • Maximum short-circuit rating
  • Approved breaker positions
  • Neutral-connection design

You should also compare the existing breaker’s complete number, not just its QDF suffix. The H, HH or N suffix changes the interrupting rating or neutral arrangement.

This is important in older Siemens, ITE or Murray equipment. If you’re working with legacy Murray equipment, review the Murray MP-T replacement guide for checking panel labels and documented Siemens relationships.

Replace a QDF Breaker

When Should You Replace a QDF Breaker?

You may want replacement when the breaker has visible damage, overheated terminals, discoloration, a cracked case, a loose bus connection or an operating mechanism that won’t reset correctly.

Repeated tripping doesn’t always mean the breaker has failed. A trip can indicate:

  • An overload or short circuit
  • A ground fault
  • A hazardous arcing condition
  • Incorrect neutral wiring
  • A shared or crossed neutral
  • A damaged cord or connected appliance

Because a QDF breaker monitors several conditions, troubleshooting the cause before you replace it. Replacing the breaker without correcting the circuit problem can lead to device tripping for the same reason.

For a closer look at AFCI-only protection, see Relectric’s Siemens QAF breaker guide.

Select a Replacement

How to Select the Correct Siemens QDF Replacement

Begin with the full catalog number on the existing breaker. Then confirm:

  1. Amperage: Match the branch-circuit rating, normally 15 or 20 amps.
  2. Voltage and poles: QDF models covered here are one-pole, 120-volt breakers.
  3. Interrupting rating: Don’t substitute a lower rating for a 22 or 65 kA model.
  4. Neutral connection: Distinguish pigtail from plug-on-neutral construction.
  5. Panel compatibility: Confirm the breaker type on the load-center label.
  6. Protective functions: Preserve both AFCI and Class A GFCI protection.
  7. Conductor suitability: Verify conductor size, material and terminal requirements.

Photograph the existing breaker label, panel label, wiring diagram and neutral connections before ordering. Those images help an electrical supplier determine exactly which breaker you need.

Find QDF Breakers

Finding New and Reconditioned Siemens QDF Breakers

Relectric lists both Q115DF and Q120DF breakers in its Siemens and ITE inventory. Depending on availability, you can find new surplus, used or tested equipment.

Provide the supplier with the full catalog number and load-center information. Don’t request only a “15-amp Siemens dual-function breaker,” because that description doesn’t specify the interrupting rating, neutral arrangement or approved breaker type.

If the panel label is unreadable, the neutral assembly is damaged or the bus shows overheating and pitting, replacing the load center might be more appropriate than installing another breaker.

QDF Breaker Summary

What You Should Know

A Siemens dual-function circuit breaker protects against overloads, short circuits, arc faults and Class A ground faults in one device. The standard Q115DF and Q120DF models belong to Siemens Type QFGA2, while the H, HH and N suffixes identify important rating or connection differences.

Your safest replacement process is to record the complete breaker number, verify the load-center label and match every electrical and physical characteristic. This helps you keep the original protection and avoid selecting a breaker that appears to fit.

Siemens QDF dual-function breaker replacement

Siemens QDF Breaker FAQ

What is a Siemens QDF dual-function breaker?+
A Siemens QDF breaker combines thermal-magnetic overcurrent protection, combination-type AFCI protection and Class A GFCI protection in one branch-circuit breaker. Common QDF models are one-pole, 120-volt breakers rated 15 or 20 amps.
What does QDF mean on a Siemens breaker?+
QDF appears in Siemens catalog numbers for dual-function AFCI/GFCI breakers, including Q115DF and Q120DF. The complete catalog number also communicates amperage and may include suffixes identifying the interrupting rating or neutral configuration.
Is Siemens QDF the same as Type QFGA2?+
They are related designations. QDF is used in catalog numbers, while QFGA2 is Siemens’ type designation for standard 10 kA plug-in dual-function breakers. QFGAH2 and HQFGA2 identify higher interrupting-rating versions, and QFGA2N identifies plug-on-neutral models.
What is the difference between Q115DF and Q120DF?+
The Q115DF is a 15-amp breaker, while the Q120DF is a 20-amp breaker. Both are normally one-pole, 120-volt, 10 kA dual-function models. You can’t substitute the 20-amp model for the 15-amp model unless the entire branch circuit is designed and approved for 20 amps.
Can Q115DFN replace Q115DF?+
Not automatically. Q115DFN is a plug-on-neutral breaker, while Q115DF uses a neutral pigtail. The plug-on-neutral model requires a compatible load center designed and labeled for that breaker type. Confirm the panel label, neutral arrangement and Siemens documentation before substituting either version.
Can a standard Siemens QP breaker replace a QDF breaker?+
A standard QP breaker shouldn’t replace a QDF breaker when the circuit requires AFCI and GFCI protection. Although both breaker families may provide overload and short-circuit protection, a standard QP model doesn’t provide the combined protective functions of a QDF breaker.
Why does a Siemens QDF breaker keep tripping?+
Repeated tripping can indicate an overload, short circuit, ground fault, hazardous arcing condition, incorrect neutral wiring, shared or crossed neutral, damaged cord or faulty connected equipment. Troubleshoot the circuit before assuming the breaker has failed.

Siemens QDF Breaker Glossary

Term Definition
AFCI Arc-fault circuit interrupter. A protective device that monitors a circuit for characteristics associated with hazardous electrical arcing.
Class A GFCI Ground-fault protection intended for personnel. Siemens identifies 5 mA Class A GFCI protection for the QDF family.
Combination-type AFCI An AFCI designed to respond to qualifying series and parallel arcing conditions within its listed operating parameters.
Dual-function breaker A circuit breaker that combines AFCI and Class A GFCI protection with overload and short-circuit protection.
GFCI Ground-fault circuit interrupter. A device that responds when current imbalance indicates leakage from the intended circuit path.
Interrupting rating The maximum prospective fault current a breaker is designed to interrupt safely at its specified voltage, commonly stated in kA.
Neutral pigtail A factory-connected neutral conductor extending from the breaker for connection to the load center’s neutral bar.
Plug-on neutral A breaker connection that attaches directly to an approved neutral rail instead of using a separate neutral pigtail.
QDF The designation used within Siemens dual-function breaker catalog numbers such as Q115DF and Q120DF.
QFGA2 The Siemens type designation associated with standard 10 kA plug-in QDF dual-function breakers.
Thermal-magnetic trip A trip system using a thermal response for sustained overloads and a magnetic response for high-current short circuits.