GRP Ex terminal box

Construction and Material

The HARDO HTB1P is an explosion-protected terminal box manufactured in GRP (glass fibre reinforced polyester) and certified for use in explosive atmospheres in accordance with the ATEX Directive (2014/34/EU) and the IECEx standard. The terminal box is approved for Zone 1, 2, 21 and 22 and is suited for demanding industrial environments, including the chemical, petrochemical and energy sectors, where low weight, high corrosion resistance and UV resistance are essential.

The GRP material complies with ISO 4892 and UL 746C and exhibits a strength reduction of only 10–15% over 20 years. UV erosion affects the surface appearance only, not the impact or flexural strength. The enclosure features solid walls of 4.5–9 mm, ensuring high structural rigidity and allowing multiple thread engagements. The lid is sealed with a silicone gasket and secured with AISI 316L stainless steel screws torqued to 2 Nm. Internal mounting screws are likewise manufactured in corrosion-resistant materials. The HTB1P is part of HARDO's complete range of increased safety enclosures, also available in copper-free aluminium (HTB1A) and stainless steel (HTB1S).

Applications

The HTB1P series is used as terminal boxes, junction boxes, control stations, instrument housings, disconnects and switches, battery containers, alarm panels and lighting controls in hazardous areas. The enclosure supports protection types Ex e (increased safety), Ex i (intrinsic safety) and combined Ex e/Ex i configurations. It is suitable for both indoor and outdoor installation in Zone 1 and 2 (gas) and Zone 21 and 22 (dust).

Customisation and Configuration

HTB1P is available in 13 standard sizes from 80×75 mm to 410×405 mm (external dimension A×B) and can be supplied with up to three DIN rails, a PE/PA rail for earth conductors, cable gland plates in stainless steel or brass, and external earth connection via bolt or gland. The series is also available as predefined junction boxes with factory-fitted terminal blocks and cable glands, ready for installation. Contact Particulair with your requirements and we will coordinate a solution directly with the manufacturer.

What Does the Enclosure Contain, and What Is Selected at the Time of Order?

The HTB1P is supplied as a certified enclosure with threaded holes, a lid with silicone gasket and AISI 316L stainless steel screws. The contents depend on the configuration ordered. Below is an overview of the components that may be included. See the full technical data sheet for complete tables of terminal block capacity and number of glands per enclosure size.

DIN Rail

The enclosure can be supplied with up to three DIN rails in hot-dip galvanised steel, stainless steel or copper. Rails can be mounted horizontally or vertically in three profile sizes: low (35×7 mm), high (35×15 mm) and mini (15×5.5 mm). A mounting plate allows up to three rails to be combined in different orientations and heights and can be integrated with an earth plate for equipotential bonding.

Terminal Blocks

The terminal blocks are certified Phoenix Contact components and are available in eight types: feed-through terminals (UT, MUT, PT, MPT), high feed-through terminals for large cross-sections (UKH), earth terminals (USLKG) and distribution terminals (RBO, RBO-HC). They cover conductor cross-sections from 2.5 mm² to 120 mm², can be labelled to customer requirements and have an operating temperature of −50°C to +120°C. The number of terminal blocks per enclosure depends on enclosure size, rail layout and conductor cross-section, and is shown in the dimension table in the technical data sheet.

PE/PA Rail for Earth Conductors

A dedicated PE/PA rail can be mounted along any enclosure wall and takes over the earth conductors from the DIN rail. This reduces the number of costly terminal blocks and in many cases allows a smaller enclosure to be selected. The rail is available in earthed and isolated versions, and a special coupler equalises the potential between the earth rails and the DIN rail without additional wire connections.

Cable Glands

The HTB1P is pre-drilled for metric threads M12–M63 and can be supplied with Ex cable glands for armoured cable or unarmoured cable in four materials: polyamide, brass, nickel-plated brass and stainless steel. Polyamide glands are suited for operating temperatures up to +70°C, while metal glands cover −55°C to +160°C. The number of glands per wall depends on enclosure size and thread size.

Earth Plates and Earth Tags

Metal cable glands require equipotential bonding. The HTB1P can be supplied with an earth plate in brass or stainless steel (2 mm or 3 mm thickness), which secures the connection for all metal glands on one enclosure wall and can be integrated into the mounting plate. A single earth tag in nickel-plated brass is a more cost-effective alternative when up to two metal glands are mounted on the same enclosure wall.

External Earth Connection

External earth connection is established via a dedicated earthing bolt (M6 for conductors up to 30 mm², M10 for conductors up to 120 mm²) or a cable gland for large conductor cross-sections. Enclosure protection is IP66, and the operating temperature is −55°C to +160°C for the bolt and −55°C to +70°C for the cable gland.

Drain and Breather Valve

A drain and breather valve can be fitted at the lowest point of the enclosure with an O-ring seal, maintaining IP66 protection and preventing condensation. The valve withstands torques up to 20 Nm and operating temperatures from −50°C to +230°C.

Configuration Examples

The HTB1P is available in six well-proven configurations covering the most common installation scenarios in hazardous areas, including a range of predefined junction boxes ready for installation.

Example 1: Predefined junction box, ready for installation

For standard applications, the HTB1P is available as a factory-assembled junction box with terminal blocks and cable glands fitted at the factory. Two enclosure sizes (80×75 mm and 80×110 mm) are supplied with 2, 3 or 4 cable glands in M25 and feed-through terminals for L, N and PE, ready for installation. Order numbers: HTB1P 080806 S02001, S02002, S03001 and HTB1P 081106 S04001, S04002.

Example 2: Optimised design with vertical DIN rail

A vertical DIN rail halves the number of terminal blocks and allows a smaller enclosure to be used. The elongated enclosure provides extra space for bending thick cables. An integrated mounting plate combined with an earth plate ensures equipotential bonding and further reduces the terminal count.

Example 3: Standard design with horizontal DIN rail

A horizontal DIN rail is the classical solution for terminal boxes. The enclosure is supplied without a PE/PA rail, and earth conductors are routed directly to the terminal blocks. An integrated mounting plate combined with an earth plate ensures equipotential bonding.

Example 4: Standard design with PE/PA rail

A PE/PA rail along the enclosure wall takes over the earth conductors from the DIN rail. This reduces the number of terminal blocks and in many cases allows a smaller enclosure to be selected. A special coupler equalises the potential between the earth rails and the DIN rail without additional wire connections.

Example 5: Metal cable glands earthed via brass plate

A brass plate (2 mm or 3 mm) ensures equipotential bonding for all metal glands on one enclosure wall and can be integrated directly into the mounting plate. This solution is well suited when three or more metal glands are mounted on the same enclosure wall.

Example 6: Metal cable glands earthed via copper washer

An earth tag in nickel-plated brass is a more cost-effective alternative to the brass plate when up to two metal glands are mounted on the same enclosure wall. The earth tag is placed directly under the gland nut and ensures the required electrical connection.

Catalogues and Data Sheets

Related Technical Knowledge

FAQ

Which zones is the HTB1P approved for?
The HTB1P is approved for Zone 1 and 2 (gas) and Zone 21 and 22 (dust) in accordance with the ATEX Directive (2014/34/EU) and the IECEx standard.

What is the IP rating of the HTB1P?
The HTB1P carries enclosure protection class IP66, meaning the enclosure is fully dust-tight and protected against powerful water jets. This makes it suitable for both indoor and outdoor installation in demanding environments.

Can the HTB1P be used outdoors?
Yes. The HTB1P is certified for both indoor and outdoor installation. The standard ambient temperature range is −20°C to +40°C, and with the extended specification −50°C to +95°C is covered, making the enclosure suitable for installation in widely varying climatic conditions.

What are the advantages of GRP over aluminium or stainless steel?
GRP (glass fibre reinforced polyester) combines low weight with high corrosion and UV resistance and is non-conductive, eliminating the need for certain types of equipotential bonding measures. GRP is particularly well suited to the chemical industry, coastal environments and plants with aggressive atmospheres. Aluminium and stainless steel are relevant choices in other contexts. Contact Particulair for advice on the right material for your project.

Which protection types does the HTB1P support?
The HTB1P supports Ex e (increased safety), Ex i (intrinsic safety) and combined Ex e/Ex i configurations. Components with Ex db, Ex ia/ib and Ex mb can likewise be mounted with their own component certificates.

Which cable glands can be used with the HTB1P?
The HTB1P is compatible with cable glands in metric threads M12–M63. The enclosure is supplied with threaded holes in the base and sides, and up to two nickel-plated brass earth bonding washers can be fitted per wall. See HARDO's complete range of Ex cable glands for dimensions and specifications.

Can the enclosure be customised?
Yes. The HTB1P is available in 13 standard sizes and can be supplied with up to three DIN rails, a PE/PA rail, cable gland plates and an external earth connection. Predefined junction boxes with factory-fitted terminal blocks and cable glands are also available. Contact Particulair with your specifications and we will find the right solution.

What information do I need to provide to receive a quote?
To enable us to provide an accurate quote quickly, it is helpful to know:

• Enclosure size or required internal dimensions
• Zone classification (Zone 1, 2, 21 or 22)
• Number of units
• Requirements for cable glands (type, quantity and cable diameter)
• Requirements for DIN rails, terminal blocks and mounting plates

Contact Particulair and we will help specify the right configuration directly with HARDO.

What is the lead time?
HARDO fulfils 92% of orders within 2–8 working days.

How do I place an order?
The HTB1P is supplied on a quote basis. Contact Particulair with your specifications and we will help identify the right size and configuration.

Technical Documentation