Explosion Proof
Explosion-Proof Circuit Breakers for Hazardous Locations
Explosion-proof circuit breakers are specifically constructed and certified for use in hazardous locations where flammable gases, vapors, or combustible dusts may be present. Within Galco's circuit breakers category they occupy a distinct position from molded case and miniature circuit breakers designed for general-purpose installations. The term "explosion-proof" refers to an enclosure design that can contain an internal arc or ignition and prevent it from propagating to the surrounding atmosphere, not to a breaker that prevents an explosion from occurring externally. A device marked "explosion-proof" without specific hazardous location certification markings indicating Class, Division, and Group is not a valid substitute for listed equipment in a classified area.
Selecting the correct explosion-proof circuit breaker starts with the area's electrical classification, which must be determined by a qualified engineer before any equipment is specified. Under the NEC Class/Division system used in North America, Class I locations involve flammable gases or vapors, Class II involves combustible dusts, and Class III involves ignitable fibers. Each class is further divided into Division 1 (hazardous conditions present under normal operation) and Division 2 (hazardous conditions present only under abnormal conditions). Within Class I and Class II, the specific material present determines the Group designation, which the breaker's certification must explicitly cover. The Zone system, used under IEC/ATEX standards for international installations, maps to the Division system but uses different designations and certification marks. Equipment certified for one classification system is not automatically acceptable under the other without specific cross-certification.
Beyond area classification, temperature class (T-code) is a critical selection parameter. The T-code on the equipment specifies the maximum surface temperature the device will reach under fault conditions, which must be below the auto-ignition temperature of the materials present in the classified area. Voltage rating, interrupt capacity, and trip characteristics follow the same selection logic as general-purpose breakers, but the pool of available options narrows considerably once hazardous location certification requirements are applied. For circuit protection requirements in non-hazardous areas of the same facility, Galco's molded case circuit breakers, electronic circuit breakers, and ground fault circuit breakers cover the broader range of industrial protection requirements. Accessories for hazardous location installations, including conduit sealing fittings and mounting hardware, are available through Galco's circuit breaker accessories category.
Frequently Asked Questions
Can I use a standard circuit breaker in a Division 2 hazardous location?
Division 2 locations have more flexibility than Division 1, but circuit breakers and other arcing devices still require equipment rated and certified for the specific Class and Group present, even in Division 2. General-purpose equipment is only permissible in Division 2 for specific equipment types that do not produce arcs or sparks during normal operation. Circuit breakers, by their nature, produce arcs during operation and tripping, so a standard general-purpose breaker is not an acceptable substitution in any Division 2 area without a specific engineering evaluation and AHJ (Authority Having Jurisdiction) approval. Explosion-proof equipment certified for Division 1 is always acceptable in Division 2 of the same Class and Group, though it typically carries a higher cost than Division 2-specific equipment.
What does the Group designation mean on an explosion-proof circuit breaker?
The Group designation identifies which specific flammable materials the equipment is certified for use with, based on the material's combustion characteristics. For Class I locations, Groups A through D cover flammable gases and vapors with progressively less severe ignition characteristics, from acetylene (Group A) through propane and similar materials (Group D). For Class II locations, Groups E, F, and G cover metal dusts, carbonaceous dusts, and grain/flour dusts respectively. The breaker's certification marking must include the Group that matches the materials present in the classified area. Using equipment certified for a less severe Group in an area containing a more severe Group material is not a compliant installation regardless of the Class and Division match.
Is explosion-proof equipment the same as intrinsically safe equipment?
No. These are two different protection techniques with different applications. Explosion-proof equipment uses a robust enclosure designed to contain any internal arc or ignition and prevent it from reaching the surrounding atmosphere. Intrinsically safe (IS) circuits limit the electrical energy available in the circuit to levels below what is capable of igniting the hazardous atmosphere, eliminating the ignition source rather than containing it. IS protection is commonly applied to instrumentation and control circuits, particularly in Division 1 locations where the low energy levels required make it practical. Explosion-proof construction is generally applied to higher-energy equipment like circuit breakers, motor starters, and receptacles where intrinsic safety is not practical. The two approaches are governed by different standards and require different installation practices.