Hazardous Area Heating Equipment NEC 500 and 505 Comparison

We offer a range of hazardous area heaters, all ETL approved to UL and CSA hazardous location standards. This document details the specific hazardous location markings of each product and the differences between them.

Types of Hazardous Area Heaters

Class 1 Induction Base
Class 1 Induction Base
Half Height Induction Heater
Half Height Induction Heater

The Induction Heaters are energy efficient, no maintenance heaters for drums and containers up to 55Gal (205L). These hazardous area heaters have the following markings:

Full Size:
Class I/Division 1/Zone 1 AEx e IIC 170°C (T3) Gb
Class I/Division 1/Zone 1 Ex e IIC 170°C (T3) Gb

Bottom Heating:
Class I/Division 1/Zone 1 AEx e IIC 200°C (T3) Gb
Class I/Division 1/ Zone 1 Ex e IIC 200°C (T3) Gb
Conforms to UL Std.60079-0, UL Std. 60079-7, ANSI/UL Std. 499
Certified to CAN/CSA Std. C22.2 No.60079-0, CAN/CSA C22.2 No.60079-7, CAN/CSA C22.2 No.88

Induction Heaters

Class 1 Heating Jacket

The Class I, Division 1, Zone 1 heating jackets are available in many standard and custom sizes for heating containers in Division 1, Zone 1 Hazardous Locations. These hazardous area heaters have the following markings:

Class I, Division 1, Zone 1, IIC T3 ;
Class II, Div. 2, Groups EFG, T3
AEx e IIB+H2 T3 Gb,
Ex e IIB+H2 T3 Gb,

Class II Zone 21 dust marking and T4 marking available on request

Conforms to UL Std.60079-0, UL Std. 60079-7, UL Std. 60079-31, ANSI/UL Std. 499 Certified to CAN/CSA Std. C22.2 No.60079-0, CAN/CSA C22.2 No.60079-7, CAN/CSA Std. C22.2 No.60079-31, CAN/CSA C22.2 No.130

Heating Jackets for Class 1, Division 1, Zone 1

CID2:
Class 1 Division 2 Heating Jacket

The Class I Division 2 range of heating jackets are available for many container sizes as well as virtually any custom size. Available in many power and temperature options, they have the following markings:

Class I, Division 2, Groups ABCD, T3
Class II, Division 2, Groups EFG, T3
Class I, Zone 2, IIC, T3
Class II, Zone 22, IIIB, T3
Class III, Division 1 and 2, T3

T4 marking available on request

Conforms to ANSI/UL Std. 499, ISA Std. 12.12.01
Certified to CAN/CSA C22.2 No.130

Heating Jackets for Class 1, Division 2

NEC 500 / NEC 505
The National Electric Code defines Hazardous Locations according to 2 different standards; NEC 505 and NEC 500. NEC 505 defines the Zone System and NEC 500 defines the Division System.
The National Electric Code Comparison
Area Classification

Our hazardous area heaters are certified to Class 1, Division 1, Zone 1 extending our level of protection into Division 1. The Zone classification system divides Division 1 into two zones. Zone 0 is generally only considered for mining applications, underground, or for very high concentrations of explosive gas that occur continuously. Therefore, where most industrial applications state Division 1, it will be equivalent to the Zone 1 certification. The final decision should rest with the user’s risk assessment of the area in question.

Comparison and Explanation of Classes, Divisions & Zones

NEC 505 defines the following:

Zone Definitions

A place in which an explosive atmosphere in the form of a gas/vapor (or cloud of combustible dust) in air…

Zone 0 (Zone 20)

…is present continuously, or for long periods or frequently.

Zone 1 (Zone 21)

…is likely to occur in normal operation occasionally.

Zone 2 (Zone 22)

…is not likely to occur in normal operation but if it does occur, will persist for only a short period.

NEC 500 defines the Division System:

Class/Division Definitions

Class I – Contains flammable gasses or vapors in quantities large enough to produce an explosion.

Class II – Is hazardous due to the presence of combustible dust in the air.

Class III – Contains easily ignitable fibers or flyings in the air. However, the quantity of fibers and flyings suspended in the air are not likely to be large enough to cause an explosion.

Division 1 – There is a high probability of an explosive atmosphere in normal operation. This can be for part of the time, up to all the time.

Division 2 – There is a low probability of an explosive atmosphere present during normal operation.

Marking Explanations

The gas group IIC and the temperature classification T3 indicate that both may be used with all of the listed gases in each of the temperature classification categories T1, T2, and T3 and correlate to NEC 500 Gas Groups A through D.

The 338F/170°C marking indicate that these hazardous area heaters will not exceed this temperature under normal operating conditions (includes 10% over-voltage and 104°F(40°C) ambient). The equivalent maximum temperature marking is 392F/200°C Bottom Heating product. It is important to note that when determining which temperature classifications are appropriate for the area of use, reference should be made to the auto-ignition temperature of the gasses present, rather than the flash point. These NEC 505 temperature classifications directly correlate to the temperature classifications outlined in NEC 500. Please see the charts below:
Hazardous Atmosphere Category

The following table give details of the types of gasses found in each group and their corresponding T-rating.

CHR Hazardous Area Heating Products and Standards - graph 4.

Explanation of T-rating temperatures

CHR Hazardous Area Heating Products and Standards - graph 5.