DIN Rail Terminal Block Selection Guide: Current Ratings, Materials, and Mounting Standards
TL;DR
- Select DIN rail terminal blocks by matching the rated current (24A to 232A) to your circuit load, with conductor cross-section as the primary physical constraint.
- PA66 with V-0 flammability rating is the preferred housing material for industrial control cabinets, operating reliably from -40C to +120C.
- TS35 (35x7.5mm) per EN 60715 is the standard mounting profile; verify rail type and material thickness (1.0±0.1mm) before ordering.
- UL 1059 for North America and CE/IEC 60947-7-1 for the EU market are the minimum certifications your terminal block must carry.
- Spring-clamp types reduce installation time by approximately 40% compared to screw-type blocks, making them cost-effective for high-density control panels.
Selecting the right DIN rail terminal block for an industrial control panel requires matching three parameters: the current rating must exceed the maximum circuit load by at least 20%, the housing material must withstand the operating environment, and the mounting profile must comply with EN 60715 standards. This guide walks through each specification with quantifiable data and real-world application notes.
In over a decade of manufacturing terminal blocks for OEMs across North America, Europe, and Southeast Asia, we have seen the same selection mistakes repeated — oversized blocks for low-current signals, undersized rails for heavy multi-level blocks, and material mismatches that lead to field failures. This guide exists to eliminate those errors.
What Are the Current Ratings for DIN Rail Terminal Blocks?
DIN rail terminal block current ratings range from 24A for standard 2.5mm2 feed-through blocks up to 232A for heavy-duty 95mm2 power blocks, as specified by IEC 60947-7-1 and UL 1059 standards.
Every terminal block has two current ratings: the rated operational current (Ie) per IEC 60947-7-1 and the UL-rated current. They are often — but not always — identical. The actual current a block can carry depends on the conductor cross-section, ambient temperature, and whether the block is installed in a single-layer or stacked configuration.
Standard Current Ratings by Wire Cross-Section
| Wire Cross-Section (mm2) | AWG Equivalent | Rated Current (IEC 60947-7-1) | Rated Current (UL 1059) | Typical Application |
|---|---|---|---|---|
| 1.5 mm2 | AWG 16 | 17.5 A | 15 A | Sensor / signal wiring |
| 2.5 mm2 | AWG 14 | 24 A | 20 A | General control circuits |
| 4 mm2 | AWG 12 | 32 A | 30 A | Motor control / power distribution |
| 6 mm2 | AWG 10 | 41 A | 40 A | Branch circuits / lighting panels |
| 10 mm2 | AWG 8 | 57 A | 50 A | Main power feeds |
| 16 mm2 | AWG 6 | 76 A | 65 A | Incoming supply / large loads |
| 35 mm2 | AWG 2 | 125 A | 110 A | Main bus / heavy machinery |
| 95 mm2 | AWG 4/0 | 232 A | 200 A | Transformer / large motor feeds |
Derating Factors You Cannot Ignore
Every terminal block must be derated when installed in a high-density configuration or at ambient temperatures above 40C. Based on IEC 60947-1 general rules, multiply the rated current by:
- Ambient temperature at 60C: derate to 80% of rated current
- Ambient temperature at 80C: derate to 65% of rated current
- Stacked multi-level blocks (3+ levels): derate to 85% per level
- Enclosed panel with limited ventilation: derate to 80% minimum
Which Housing Material Should You Choose?
PA66 (Nylon 66) with V-0 flammability rating is the standard choice for DIN rail terminal block housings, operating from -40C to +120C, while polycarbonate (PC) is preferred for transparent applications requiring higher tracking resistance.
| Property | PA66 (Nylon 66) | Polycarbonate (PC) | Thermoplastic Polyester |
|---|---|---|---|
| Flammability | V-2 / V-0 | V-2 / V-0 | V-0 |
| Operating Temperature | -40C to +120C | -40C to +125C | -40C to +140C |
| CTI | CTI 600 | CTI 250-400 | CTI 600 |
| Chemical Resistance | Good | Moderate | Excellent |
| UV Resistance | Poor | Good | Moderate |
| Relative Cost | Baseline | 10-15% higher | 20-30% higher |
What Are the DIN Rail Mounting Standards?
DIN rail terminal blocks mount on TS35 (35mm width, 7.5mm or 15mm depth) or TS32 (32mm width) profiles as defined by EN 60715 and DIN EN 50022, with TS35 being the industry standard for over 90% of industrial control panels.
| Profile | Width | Height/Depth | Material Thickness | Standard |
|---|---|---|---|---|
| TS35x7.5 | 35±0.3 mm | 7.5±0.15 mm | 1.0±0.1 mm | EN 60715 / DIN EN 50022 |
| TS35x15 | 35±0.3 mm | 15±0.15 mm | 1.5±0.15 mm | EN 60715 / DIN EN 50022 |
| TS32x15 | 32±0.3 mm | 15±0.15 mm | 1.5±0.15 mm | EN 60715 |
| TS15x5.5 | 15±0.2 mm | 5.5±0.1 mm | 1.0±0.1 mm | DIN EN 50045 |
How DIN Rail Terminal Blocks Mount
Most modern DIN rail terminal blocks use a tool-less snap-on locking mechanism: the block engages the top lip of the rail first, then rotates downward until the spring-loaded foot snaps onto the bottom lip.
- Align the terminal block at a 15-20 degree angle, hooking the upper clip onto the top edge of the TS35 rail.
- Rotate the block downward until the bottom spring foot contacts the lower rail edge.
- Press firmly — you should hear an audible click as the tension spring locks into position behind the rail.
- Verify engagement by attempting to lift the block upward without pressing the release tab.
UL vs CE Certification: What Engineers Must Verify
For North American projects, UL 1059 certification is mandatory covering terminal blocks up to 600V; for EU projects, CE marking per IEC 60947-7-1 is the legal requirement, and many projects also require TUV or VDE certification.
| Parameter | UL 1059 | IEC 60947-7-1 |
|---|---|---|
| Voltage Rating | 300V / 600V | 250V / 400V / 690V |
| Current Test Method | 45C temperature rise limit | 45K temperature rise limit |
| Wire Testing | Solid and stranded (separate) | Same tests apply |
| Pollution Degree | Not specified | PD 2 / PD 3 |
| Flammability | UL 94 V-2 or V-0 | IEC 60695-11-5 (glow wire) |
| Third-Party Testing | UL or recognized NRTL | TUV, VDE, or notified body |
How to Verify Certifications Before Ordering
- UL certificate: Verify the UL file number on the UL Product Database.
- CE Declaration of Conformity: Must reference IEC 60947-7-1. Verify on IEC official site.
- TUV or VDE certificate: Verify on TUV Rheinland or VDE databases.
- RoHS and REACH declarations: Required for EU market entry.
How to Select the Right Terminal Block Type
The seven main types of DIN rail terminal blocks — feed-through, ground, fuse, disconnect, multi-level, sensor, and power distribution — each serve a distinct wiring function.
| Type | Primary Function | Current Range | Key Feature |
|---|---|---|---|
| Feed-Through | Connect and distribute wires | 17.5A – 232A | Single conductor path, 2-in/2-out |
| Ground (PE) | Earth / protective ground | Same as feed-through | Green-yellow; connects to rail |
| Fuse | Circuit protection | 6.3A – 63A | Built-in fuse holder |
| Disconnect | Isolate circuit without removing wire | 17.5A – 76A | Sliding lever or knife switch |
| Multi-Level | Stack circuits to save panel space | 17.5A – 32A per level | 2-4 stacked levels |
| Sensor / Thermocouple | Transmit low-voltage signals | 2A – 10A | Special alloy contacts |
| Power Distribution | Distribute main power | 76A – 232A | Large cross-section; multiple outlets |
Screw Type vs Spring-Clamp: Connection Technology Comparison
Screw-type terminal blocks offer higher clamping force (3-5 Nm) for high-current applications above 100A, while spring-clamp blocks provide faster wiring (approximately 40% less installation time) and dominate control cabinet wiring for 24A to 65A ranges.
| Dimension | Screw-Type | Spring-Clamp |
|---|---|---|
| Installation Time per Wire | 8-12 seconds | 3-5 seconds |
| Clamping Force | 3.0 – 5.0 Nm | 0.5 – 1.5 Nm |
| Vibration Resistance | Excellent (when torqued) | Excellent (self-adjusts) |
| Re-termination Cycles | 50+ cycles | 200+ cycles |
| Wire Range | 0.2 – 95 mm2 | 0.14 – 16 mm2 |
| Relative Cost per Position | Baseline | 15-25% higher |
Screw-Type vs Spring-Clamp vs IDC: Five-Dimension Comparison
Comparing across five quantifiable dimensions, spring-clamp offers the best balance for 90% of industrial control applications, while screw-type dominates high-current and IDC dominates high-production pre-wired systems.
| Dimension | Screw-Type | Spring-Clamp | IDC |
|---|---|---|---|
| 1. Max Current | Up to 232A | Up to 65A | Up to 24A |
| 2. Installation Time | 8-12 sec | 3-5 sec | 2-3 sec |
| 3. Wire Range | 0.2-95mm2 | 0.14-16mm2 | Single AWG per model |
| 4. Re-termination | 50+ cycles | 200+ cycles | 1-3 cycles |
| 5. Cost Ratio | 1.0x | 1.15-1.25x | 0.85-0.95x |
Which One Should You Choose?
Choose Screw-Type when: circuit current exceeds 65A, wire cross-section exceeds 16mm2, high-vibration environment, or service staff trained with torque tools.
Choose Spring-Clamp when: application is 65A or below (covers >85% of industrial circuits), wiring speed is priority, or frequent wire changes expected.
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