NB-HEPTX-NXT-HEADS

Supported Applications

The Omega NB, NEP-T, and NXT series provides thermocouple heads and terminal blocks designed for connection head assemblies. These protection heads are engineered to house sensor elements in industrial environments requiring moisture and dust resistance. The product overview identifies suitability for outdoor use across multiple housing configurations.

• Outdoor installations
• Chemical plant applications (specifically Nylon NBN models)
• Hazardous locations: Class I, Group C, D; Class II, Groups E, F, G; and Class III (explosion-resistant heads only)

Note: The use of explosion resistant heads does not imply that a complete assembly is either explosion proof or intrinsically safe. It is the user's responsibility to determine suitability of materials for an installation.

Operating Conditions & Performance

The series supports various terminal block configurations with 0, 2 (single element), or 4 terminals (duplex element). Wire capacity varies by model; standard heads accommodate max 14-gage wire, while specific heavy-duty cast iron models support up to max 8-gage wire. The Nylon NBN head is suitable for use in ambient temperatures to 121°C (250°F).

Protection tube and extension wire entry connections are provided via threaded openings or compression fittings depending on the housing type.

• NPT Threads: Common sizes include ½ NPT, ¼ NPT, ¾ NPT, and 1 NPT for protection tube and wire entry.
• Metric/BSPP: Some models feature M10 x 1 or M16 x 1.5 compression fittings; the NB9 model utilizes ½ BSPP threads.

Certain explosion-resistant heads (NEPA, NEPB) are rated for Class I, Group C, D; Class II, Groups E, F, G; and Class III environments. The HEP-TX series is specifically noted as an explosion resistant head for 2-wire transmitters, rated for Class I, Div 1&2, Groups C, D; Class II, Div 1, Groups E, F, G; and Class III.

Configuration Options

The series offers a broad envelope of housing materials and form factors to accommodate different installation constraints. Available configurations include standard sizes, deep base, flip-top, domed top, low profile, miniature, and explosion-resistant designs.

• Housing Materials: Cast Iron (NB1, NB5, NSA/B/C), Burnished Die-Cast Aluminum (NB2), Aluminum (NB3, NB6/7/8/11/12, NXT), Bakelite (NB10), Glass Reinforced Nylon (NB9), Nylon (NBN), Bakelite Glass Fiber (NBG), Feraloy® Iron Alloy (HEP-TX), and Cast Iron with Aluminum Cap (NEP-T).
• Terminal Blocks: Options include ceramic, bakelite, or standard blocks. Specific terminal block models such as CH-49 through CH-84 are available for various head types.
• Special Features: Models feature safety chains on covers (readily removed without tools), gasketed weather resistance, hinge tops, and bayonet covers. The NB12 Low Profile model is IP 67 Sealed.

NEMA 4X (IP66) Rated Heads are available; consult the technical department for details. Sanitary Polypropylene and Stainless Steel heads are also offered via omega.com/sanitary.

Key Product Differences

The series distinguishes models by material, physical dimensions, terminal count suffixes (-0, -2, -4), and specialized features for hazardous or high-temperature environments. Model numbers follow the pattern NB<type>-<terminal_suffix>, with examples including NB1-0 (Cast Iron, no terminals) through NEP-T4.

• Standard vs. Heavy Duty: Cast iron models like NSA and NSB are described as "rugged" heavy heads supporting max 8-gage wire, whereas aluminum variants emphasize lightweight construction.
• Hazardous Location Ratings: NEPA/NEPB (Cast Aluminum Body and Cap) and HEP-TX (Feraloy® Iron Alloy) provide explosion-resistant ratings not present in standard NB series heads. The HEP-TX70 variant is specifically configured for mounting TX70 Transmitters.
• Form Factors: Distinct physical profiles include the Deep Base (NB6), Flip Top (NB7), Domed Top (NB8), Low Profile (NB12), and Miniature sizes (NB4, NB9).

Transmitters may not be mounted in most heads; specifically, transmitters cannot be mounted in the NB4 head. Only the smallest transmitters can fit the NB2 head by special order. Barrier strips are utilized when more than 4 connections are required (e.g., dual element 3-wire RTD).