Tuesday, 8 September 2026
Hazardous Location Transformers: Class I Division 2 Requirements and Specification
A transformer installed in a hazardous location has to satisfy more than its ...
Specialty Products
Hazardous Location Transformers
Operating in hazardous environments leaves no room for compromise. In industries where flammable gases, vapours, or combustible dust are present, electrical equipment must meet strict safety standards to protect personnel, facilities, and operations. Hazardous area transformers play a critical role in ensuring dependable power delivery while minimizing the risk of ignition in these high-risk settings.
At Rex Power Magnetics, our hazardous location transformers are engineered to deliver safe, efficient, and compliant power solutions for volatile environments.
What Are Hazardous Location Transformers?
Hazardous location transformers are specially designed electrical transformers built to operate safely in environments where explosive or flammable substances may be present under normal or abnormal operating conditions.
Unlike standard transformers, these units are constructed with enhanced insulation systems, sealed enclosures, and certified designs that reduce the risk of sparks, overheating, or electrical faults that could trigger an explosion.
Key Advantages
- CSA and UL-approved designs for hazardous locations
- IECEx certification for international compliance
- Custom-built solutions based on application requirements
- Robust construction for harsh industrial environments
Our team works closely with engineers, contractors, and facility operators to ensure each transformer meets the exact electrical, environmental, and regulatory needs of the project.
Get Your Hazardous Location Transformer
If your operation requires safe and dependable power in a hazardous environment, Rex Power Magnetics is ready to help. Our hazardous location transformers are engineered to meet the highest safety standards while delivering reliable performance in the most demanding conditions.
Contact us today to discuss your hazardous location power requirements and receive a customized transformer solution designed for your application.
| Capacity |
|
| Voltage Class | 1.2kV |
| Cooling | Self Cooled (ANC) |
| Frequency | 60Hz (50/60Hz Optional) |
| Conductors | Copper (Cu) or Aluminum (Al) Windings |
| Temperature Rise |
|
| Insulation System | 200°C |
| Impregnation | Core & Coil Are Encapsulated In a Block of Polyurethane and Silica Sand |
| Primary Taps | Typically +/-2 x 2.5% Raps (Refer To Dry Type Distribution Transformer Catalog) |
| Sound Level | Meets NEMA ST-20 |
| Enclosure Type | Type 3R Indoor/Outdoor (Type 4 or IP66 Optional when used with certified watertight conduit hubs) |
| Enclosure Finish | ANSI/ASA 61 Grey |
| Warranty | 12 Months (See Warranty and Limitations) |
| Quality System | ISO 9001:2015 Quality Management System |
| Certifications |
|
| Reference Standards |
|
| Optional Features & Accessories |
|
| Capacity |
|
| Voltage Class | 1.2kV |
| Cooling | Self Cooled (ANC) |
| Frequency | 60Hz (50/60Hz Optional) |
| Conductors | Copper (Cu) or Aluminum (Al) Windings |
| Temperature Rise |
|
| Insulation System | 200°C |
| Impregnation | Core & Coil As Well As The Connections Between Leads And Coils Are Encapsulated In A Block of Polyurethane and Silica Sand |
| Primary Taps | Typically +/-2 x 2.5% Raps (Refer To Dry Type Distribution Transformer Catalog) |
| Sound Level | Meets NEMA ST-20 |
| Enclosure Type | Type 3R Indoor/Outdoor (Type 4 or IP66 Optional when used with certified watertight conduit hubs) |
| Enclosure Finish | ANSI/ASA 61 Grey |
| Warranty | 12 Months (See Warranty and Limitations) |
| Quality System | ISO 9001:2015 Quality Management System |
| Certifications |
|
| Reference Standards |
|
| Optional Features & Accessories |
|
| Capacity |
|
| Voltage Class |
|
| Cooling | Air Cooled (ANN / AN) |
| Frequency | 60Hz (50/60Hz Optional) |
| Conductors | Copper (Cu) or Aluminum (Al) Windings |
| Temperature Rise |
|
| Insulation System | 220°C |
| Impregnation | Polyester Resin Dipped and Baked |
| Efficiency | Meets North American Energy Efficiency Standards:
|
| Primary Taps | Typically +/-2 x 2.5% taps (refer to dry type distribution transformer catalogue) |
| Sound Level | Meets NEMA ST-20 |
| Enclosure Type | Type 3R Indoor/Outdoor (Type 4 or IP66 Optional when used with certified watertight conduit hubs) |
| Enclosure Finish | ANSI/ASA 61 Grey |
| Warranty | 12 Months (See Warranty and Limitations) |
| Quality System | ISO 9001:2015 Quality Management System |
| Certifications |
|
| Reference Standards |
|
| Optional Features |
|
Product Catalogs
Faqs
- General FAQs
- Technical Specification FAQs
- Installation & Application FAQs
- Performance & Product Selection FAQs
- Protection, Standards & Ordering FAQs
A hazardous location transformer is specially designed for environments where flammable gases, vapors, or combustible dust may be present. These transformers provide safe voltage conversion and isolation while preventing ignition of surrounding atmospheres. Rex Power Magnetics hazardous location transformers are engineered for use in classified areas such as refineries, chemical plants, grain processing facilities, and offshore platforms. They combine robust electrical performance with mechanical features that meet or exceed explosion-proof and environmental protection requirements.
In an HLA, the core and coil are cast in the polyurethane and silica sand block, but the joints between the winding ends and the external leads sit inside the enclosure in air. In an HLB, those connections are cast into the block as well, so nothing between the winding and the terminal board is exposed.
The failure mode this addresses is a loose or corroded splice. A bolted or crimped connection that loosens under thermal cycling or vibration develops resistance, heats locally and can eventually arc. In an unclassified area that is a reliability problem; in a Division 2 area it is a potential ignition source and a possible surface hot spot above the T-code. Encapsulating the joint removes the air gap, locks the connection mechanically and excludes the moisture and corrosive vapour that drive the degradation in the first place.
HLB is therefore the model to specify for compressor houses, pump stations and process skids where vibration is continuous, for atmospheres carrying hydrogen sulphide or chlorine-bearing vapour, and for sites where inspection access is limited. Ratings, options and enclosure choices are identical to HLA, so the decision costs nothing in electrical performance. The Knowledge Hub article on transformer failures discusses connection faults as a leading cause of field failures.
Rex describes its hazardous location transformers as CSA and UL approved for Class I, Division 2, Groups A through D. Under the Canadian Electrical Code and the NEC, Group A is acetylene, Group B is hydrogen and similar gases, Group C covers ethylene and ethyl ether, and Group D covers propane, methane, gasoline, hexane and most petroleum vapours.
The practical consequence is that the gas group on your area classification drawing rarely disqualifies a Rex unit, but the T-code can. A Group D methane area is satisfied by T2C; a Group C ethyl ether area needs a cooler surface than T3C provides and should be discussed with Rex engineering. Always transcribe Class, Division, Group and T-code from the classification document onto the purchase specification.
Yes. Rex hazardous location transformers are designed for Class I, Division 2 environments under applicable nonincendive equipment standards, including CSA C22.2 No. 213 and UL 121201.
Their enclosures contain no exposed sparking components or ignition-capable hot surfaces during normal operation. Connections and optional accessories are designed to maintain the required temperature classification (T-code). Proper overcurrent protection is essential to prevent overheating during faults or overloads.
A Rex hazardous location transformer may be suitable for combustible dust environments, but standard Class I, Division 2 certification does not automatically cover Class II locations.
Dust environments require appropriate enclosure protection, temperature ratings, and certification. For Class II applications, specify the dust group and required temperature classification, and contact Rex engineering to confirm suitability and certification.
Yes. All three families carry ±2 × 2.5 percent primary taps as standard, giving five connection positions: +5, +2.5, nominal, −2.5 and −5 percent. On the ventilated HLC the taps are brought to a terminal board inside the enclosure in the usual way. On the encapsulated HLA and HLB the tap leads exit the polyurethane and silica sand block and terminate on a board or on labelled leads, so the taps are accessible without disturbing the encapsulation.
Changing a tap is a de-energized operation, and in a Division 2 area it is also a hot-work-permit operation, because opening the enclosure exposes bare conductors. The normal sequence is:
• isolate and lock out the primary, and verify absence of voltage;
• obtain a gas test and permit under the site’s safe-work system;
• open the enclosure, move the tap connections on all phases to the same position, torque to the value in the documentation;
• restore gaskets and covers so the enclosure type rating is intact, then re-energize and verify secondary voltage.
All three families meet NEMA ST-20, which sets maximum average sound levels for dry-type transformers by kVA band. For self-cooled units, the limits run from 40 dB for ratings up to 9 kVA through 45 dB for 10 to 50 kVA, 50 dB for 51 to 150 kVA, 55 dB for 151 to 300 kVA, 60 dB for 301 to 500 kVA, 62 dB for 501 to 700 kVA and 64 dB for 701 to 1,000 kVA. A 45 kVA hazardous location transformer is therefore limited to 45 dB, and a 750 kVA HLC to 64 dB.
Within those limits, the HLA and HLB tend to run below the ventilated HLC of the same rating. Transformer noise is magnetostriction in the core laminations transmitted to the enclosure. In the encapsulated designs the core is cast into a rigid block of polyurethane and silica sand, which damps lamination vibration and decouples it from the enclosure panels; the HLC transmits core vibration through its mounting to a louvred enclosure that can itself resonate.
Sound rarely governs in a process area, but it can matter near an occupied control room. The external anti-vibration pads option, available on all three models, breaks the structure-borne path into the mounting steel, and an HLC can be ordered to a reduced sound level. The Knowledge Hub article on transformer humming noise explains the mechanisms.
Both conductors are offered on every Rex hazardous location transformer model, and the Class I, Division 2 certification applies equally to either, because the certification is about surface temperature and ignition sources rather than conductor material. The choice affects three practical things.
• Size and weight. Aluminum has about 61 percent of copper’s conductivity, so an aluminum winding needs roughly 60 percent more cross-section to reach the same resistance and the same temperature rise. The core window grows accordingly, and on an encapsulated HLA or HLB the block and enclosure grow with it. Aluminum is lighter per unit volume, so the finished unit is often similar in weight and larger in volume.
• Terminations. Aluminum winding leads are normally terminated on the transformer’s terminal board with plated lugs or transition connectors so the installer lands copper or aluminum field conductors without a dissimilar-metal joint. On an HLB, that termination is downstream of the encapsulated joint, so the connector choice does not affect the sealed section.
• Cost and delivery. Aluminum is generally the economical conductor for larger HLC ratings; copper is common on small HLA units where the material difference is small and the compact size matters.
Specify the conductor on the purchase order, or leave it to Rex to select; the Part Number Builder records the choice, and the Knowledge Hub article on transformer windings discusses both conductors.
These transformers are used wherever safe, reliable power is needed in explosive or dusty atmospheres. Common applications include oil and gas processing, petrochemical refineries, paint spray booths, fuel terminals, wastewater treatment plants, mining operations, and grain or food processing facilities. They supply power to lighting systems, control panels, sensors, and instrumentation located in hazardous areas. Rex Power Magnetics customizes each design for the environmental and operational requirements of its intended location.
Yes. These transformers are designed for both indoor and outdoor use in classified environments. Outdoor-rated models are supplied with NEMA 3R, 4, or 4X enclosures that resist moisture, corrosion, and UV exposure. The polyester resin–dipped coils and sealed enclosures prevent ingress of contaminants and condensation. When properly installed according to CSA and NEC guidelines, they provide safe, long-term operation in even the harshest outdoor or offshore environments.
Conduit sealing in a Division 2 area is governed by Section 18 of the Canadian Electrical Code and Article 501 of the NEC, which distinguish between enclosures required to be explosion-proof and those that are not. A Rex hazardous location transformer is nonincendive Division 2 equipment, not an explosion-proof enclosure, so the rule demanding a seal at every explosion-proof enclosure entry does not by itself apply at the transformer.
Seals are still required in two places on most installations. The first is at the boundary where a conduit passes from the Division 2 area into an unclassified area, so that gas cannot migrate through the raceway to the panelboard or switchgear room. The second is wherever the wiring method itself requires it, for example at the transition from certified cable to conduit, or where a Type 4 or IP66 enclosure’s ingress rating must be maintained with a sealed fitting.
Because the transformer has no arcing parts, the more important detail is usually the fitting at the enclosure: use a threaded entry with the certified hub or gland specified for the enclosure type, keep unused knockouts closed with rated plugs, and do not add field entries beyond those on the approval drawing. Confirm seal locations with the authority having jurisdiction, and refer to the Knowledge Hub article on transformer clearance requirements for the code-driven spacing around the unit.
The HLC is air cooled (AN) through enclosure louvres, so it depends on free convection as the encapsulated models do not. Rex’s dry-type guidance applies: keep at least 150 mm (6 in) of air space between the enclosure and adjacent equipment or surfaces, 300 mm (12 in) to any combustible surface, and no less than 6 mm (0.25 in) between the enclosure back and a non-combustible mounting wall.
In a classified area there are additional considerations. Position the unit where the ventilation that keeps the area at Division 2 rather than Division 1 actually reaches it; a dead corner where vapour can pool is the wrong place for heat-producing equipment. Keep the louvres clear of hose-down spray, insulation blankets and stacked material, because blocked louvres raise winding temperature and push the surface toward the T-code limit. Avoid mounting above a hot process line, since inlet air temperature is the ambient the transformer sees.
Where dust or corrosive vapour would enter through the louvres, specify the HLC in a non-ventilated Type 4, 4X or 12 enclosure and ask Rex to confirm the rating, or move to an encapsulated HLA or HLB. Outline dimensions for each enclosure type are on the Enclosure Drawings page, and the Knowledge Hub article on the role of design, environment and load in transformer lifespan covers the effect of restricted cooling.
Rex’s standard service conditions for dry-type transformers are an ambient of −30°C to +30°C average with a 40°C peak, relative humidity below 70 percent, and altitude up to 1,000 m (3,300 ft). A hazardous location transformer is certified on the same 40°C basis unless a different ambient is declared at the time of order, and that declared ambient appears on the nameplate.
Above 1,000 m the thinner air carries away less heat. IEEE C57.12.01 provides the usual guidance for self-cooled dry-type units: reduce rated kVA by about 0.3 percent for every 100 m above 1,000 m, so a unit at 2,000 m carries roughly 97 percent of nameplate. Mining sites in the Rockies and Andes are the common case, and Rex can instead design the unit for the site altitude so that the nameplate rating is usable in full.
Above 40°C ambient the derating is steeper because the winding rise is a fixed increment above ambient: a T3 unit at 115°C rise in a 50°C process building would exceed both its insulation limit and its certified surface temperature. The correct response is to order the unit designed for the higher ambient, usually a lower rise class, rather than derate in the field. Declare the true maximum ambient, including solar gain outdoors, in the specification. The Knowledge Hub article on low-ambient temperature considerations covers the cold end of the range.
It can, with two considerations. The first is harmonic heating. A six-pulse VFD draws current rich in 5th and 7th harmonics, and the additional eddy-current loss in the windings raises temperature above what the fundamental current alone would produce. On an ordinary transformer that shortens life; on a hazardous location transformer it also erodes the margin below the certified surface temperature. The K-factor option (K4, K9, K13 or K20) is offered on all three families for this reason. A transformer feeding a mix of drives and linear loads is usually K4; a unit dedicated to drive loads without line reactors is more often K13.
The second consideration is where the drives live. A VFD is an arcing and heat-producing device that needs its own hazardous location rating or must be located outside the classified boundary. The common arrangement is an HLC in the classified area supplying certified motors and instrumentation, with the drives in an unclassified electrical room, or an HLC outside the boundary feeding a drive lineup, in which case a drive isolation transformer may be the better product because it is built to IEEE C57.110 for drive duty.
The Knowledge Hub articles on K-factor transformers and VFDs and drive isolation transformers cover the harmonic side; the power quality industry page describes typical plant arrangements.
K-factor weights the harmonic current spectrum by harmonic order squared and tells the designer how much extra eddy-current loss to design out so the winding hot spot stays at rated rise. Rex offers K4, K9, K13 and K20 on all three hazardous location transformer families. The value follows the load mix:
• K4 covers a general lighting and receptacle panel with a minority of electronic loads, including LED drivers with power-factor correction.
• K9 suits panels where roughly half the load is electronic: LED lighting, small UPS units, PLC supplies and analyzers.
• K13 applies where the load is predominantly six-pulse VFDs or switch-mode supplies without line reactors.
• K20 is reserved for almost entirely non-linear load with high 5th and 7th harmonic content.
A dry-type transformer can carry short overloads because the winding has thermal mass; the IEEE C57.96 loading guide allows a modest overload after operation at partial load, at the cost of some insulation life, assuming the only consequence of running hot is accelerated aging.
On a hazardous location transformer there is a second consequence. The temperature code is a certified maximum surface temperature at rated load, and an overload that pushes the winding above its rated rise also pushes the enclosure surface toward the code limit. An 80°C-rise T3C unit has more headroom than a 115°C-rise T3 unit, but neither is certified above nameplate, and an inspector or incident investigator will treat sustained overload as operation outside the certificate.
The practical rules are:
• size the unit so continuous load is at or below 80 to 90 percent of rating, which also keeps regulation tight;
• treat motor starting and inrush as transients the winding can absorb, not as a reason to run a smaller unit;
• if the load will grow, buy the larger unit now;
• if occasional overload is unavoidable, specify the T3C rise so the design margin absorbs it.
The encapsulated HLA and HLB have a longer thermal time constant than the HLC, so they ride through short peaks with less surface temperature change. The Knowledge Hub article on transformer rating explains the loading basis.
The T-code sets the maximum surface temperature, and the gas must have an auto-ignition temperature above it: T2C is 230°C, T3 is 200°C, T3C is 160°C. Auto-ignition temperatures published in NFPA 497 and the CEC hazardous-locations tables give a working sense of which Rex hazardous location transformer code fits which atmosphere:
• Methane (about 537°C), propane (about 450°C), hydrogen (about 500°C), ethylene (about 450°C), acetylene (about 305°C): any of T2C, T3 or T3C is acceptable on temperature grounds.
• Gasoline vapour (roughly 280°C): T2C, T3 or T3C all qualify, with T3 or T3C giving more margin.
• Hexane (about 225°C), and diesel or kerosene vapours in the 210 to 260°C range: T2C at 230°C is marginal or excluded; specify T3 or T3C.
• Acetaldehyde (about 175°C): requires T3C.
• Ethyl ether (about 160°C) and carbon disulphide (about 90°C): below the range of the standard families; these need a colder code such as T4 or T6 and should be discussed with Rex engineering.
Yes. Rex Power Magnetics designs and manufactures custom hazardous location transformers to meet project-specific requirements. Options include special voltage ratings, enclosure materials, temperature-rise classes, and mounting configurations. Transformers can also be integrated into explosion-proof panels or combined with fusing and protection devices. Each custom design is fully tested and certified for its intended hazardous classification, ensuring compliance, reliability, and safe operation in demanding environments.
The nameplate follows CSA C22.2 No 47 and IEEE C57.12.01 conventions for a dry-type transformer, and adds the hazardous location marking. The electrical fields are the ones found on any Rex unit: kVA, phases, frequency, primary and secondary voltages, tap voltages and connections, percent impedance, temperature rise, insulation system class, enclosure type, weight, serial number and connection diagram reference.
The fields specific to a hazardous location transformer are the ones an electrical inspector, and later an incident investigator, will read first:
• the certification mark (CSA, UL or both) and the file or certificate reference;
• the Class and Division (Class I, Division 2) and the gas groups covered;
• the temperature code (T2C, T3 or T3C);
• the maximum ambient on which the temperature code is based, normally 40°C;
• for IECEx-marked units, the IEC marking string with equipment protection level and gas group.
Commissioning a hazardous location transformer follows normal dry-type practice with a hazardous area overlay. Before energization: verify the nameplate against the area classification and drawings; megger the windings and compare with the factory test report; confirm tap positions on all phases; check that conduit entries are sealed or plugged as required, that gaskets and covers are intact so the enclosure rating is preserved, and that bonding is continuous. If the unit has stood in an unheated space, warm it above 0°C and confirm insulation resistance first. Energize from outside the classified area under the site’s permit system.
In service the transformer needs little attention, but the certificate must be maintained. A reasonable programme is:
• monthly to quarterly: visual check of enclosure integrity, corrosion, gaskets, blocked louvres on an HLC, and signs of overheating such as discoloured paint;
• annually: de-energized inspection under permit, terminal torque check, insulation resistance test, cleaning of the enclosure and HLC louvres;
• after any fault or overload: insulation resistance test and a thermographic survey under load, since surface temperature is the certified parameter.