Multi-Level Terminal Block Symbol
Definition: The Multi-Level Terminal Block symbol represents a double-deck or multi-level DIN-rail-mounted terminal block that provides two or more independent electrical connections within a single terminal body, depicted with Top L, Top R (upper level) and Bot L, Bot R (lower level) terminals, used in control panel wiring diagrams to interconnect two separate circuits vertically within a compact footprint per IEC 60947-7-1.
Also known as: double-level terminal block, multi-deck terminal, two-level terminal, feed-through double terminal, stacked terminal block, multi-tier terminal.
What the Multi-Level Terminal Block symbol means
The Multi-Level Terminal Block symbol in a wiring diagram indicates a terminal block that provides two (or more) electrically independent connection levels stacked vertically within one housing. Unlike a single-level feed-through terminal, the multi-level block connects Top L to Top R at the upper level and Bot L to Bot R at the lower level, with no electrical connection between levels unless an internal bridge or jumper is installed.
The symbol communicates that two separate circuit conductors can be terminated in the same physical terminal unit, saving DIN-rail space in control panels. Multi-level terminal blocks are particularly useful in compact panels where two signals or circuits must be routed through the same zone of the DIN rail without cross-connecting.
How to identify the Multi-Level Terminal Block symbol
The Multi-Level Terminal Block symbol is drawn as a rectangle representing the single terminal body, with four terminals: Top L (upper-left), Top R (upper-right), Bot L (lower-left), and Bot R (lower-right). A horizontal line within the rectangle separates the upper level (Top L ↔ Top R connection) from the lower level (Bot L ↔ Bot R connection). The block may be labelled 'ML-TB', '2-level TB', or with the manufacturer reference (e.g. 'WAGO 2002' or 'Phoenix PT2×2').
Function and usage boundary
The multi-level terminal block provides two separate feed-through connections within one compact housing. The upper level connects the Top L and Top R terminals as a low-resistance through-connection; the lower level independently connects Bot L and Bot R. This allows two separate control-circuit conductors (e.g. a 24 V DC signal circuit and a 230 V AC control circuit) to pass through the same terminal position in a DIN-rail panel. Some multi-level variants offer earth (PE) connections on one level, signal on another, or power feed-through combined with a fused output on the second level.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60947-7-1 governs low-voltage switchgear and controlgear assemblies — terminal blocks for copper conductors. Multi-level terminal blocks must meet the same isolation and current ratings as single-level types; the symbol follows IEC 60617 wiring-device block conventions. |
|---|---|
| ANSI/IEEE 315 | ANSI/NEMA ICS 4 (terminal blocks) and UL 508A (industrial control panels) govern terminal blocks in North American practice. ANSI Y32.2 / IEEE 315-1975 does not define a specific multi-level terminal symbol; a rectangular block with four labelled terminals is standard practice. |
| Key difference | Both IEC 60947-7-1 and ANSI/NEMA ICS 4 govern multi-level terminal block performance requirements. Symbol representation is not specifically standardised for multi-level types; both IEC and ANSI practice uses a rectangle with labelled upper and lower terminal pairs. |
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Logical terminals
| Logical ID | Editor terminal name |
|---|---|
| top_l | Top L |
| top_r | Top R |
| bot_l | Bot L |
| bot_r | Bot R |
Where the Multi-Level Terminal Block symbol is used
- Compact control panels: multi-level terminal blocks reduce DIN-rail length by stacking two circuits in one terminal footprint where space is limited
- PLC I/O wiring: field device signals (upper level) and common/return conductors (lower level) are organised in the same terminal column
- Building automation panels: sensor supply (24 V DC) and sensor signal circuits are run through upper and lower levels of multi-level terminals
- Machine safety circuits: safety loop and monitoring circuits are segregated onto upper and lower levels of multi-level terminal blocks
- Retrofit panel upgrades: multi-level terminals replace single-level types to double the connections in an existing panel without extending the DIN rail
- Marine and rail vehicle wiring: multi-level terminals with PE ground on one level are used in vibration-resistant panels where space is at a premium
Key facts
- The Multi-Level Terminal Block symbol represents a double-deck terminal block providing two independent electrical connections (upper and lower levels) within a single housing per IEC 60947-7-1.
- The four terminals are Top L (upper level left), Top R (upper level right), Bot L (lower level left), and Bot R (lower level right), with no electrical connection between levels unless bridged.
- Multi-level terminal blocks reduce DIN-rail space requirements by up to 50% compared to using two single-level terminals for the same two circuits.
- Typical ratings are 630 V AC/DC and 16–32 A per level; minimum insulation resistance between levels exceeds 100 MΩ.
- Internal bridges or jumpers can be inserted within or between terminal block levels to create distribution groups, ganging multiple terminals together on the same level.
- Common manufacturers include Wago (2002 and 2004 series), Phoenix Contact (PT and PTTBS series), ABB (SNK series), and Weidmuller (W-Series multi-level types).
- IEC 60947-7-1 requires that the insulation between levels withstands the rated impulse voltage and pollution degree specified for the installation.
Frequently asked questions
What does the multi-level terminal block symbol mean in a wiring diagram?
The multi-level terminal block symbol means the diagram includes a double-deck terminal that provides two electrically independent connections in one compact housing. The upper level connects Top L to Top R; the lower level connects Bot L to Bot R, with no connection between levels.
What does the multi-level terminal block symbol look like?
The multi-level terminal block symbol is a rectangle divided by a horizontal line into two levels. The upper level has Top L (left) and Top R (right) terminals; the lower level has Bot L and Bot R terminals. It represents the entire double-deck terminal housing on a DIN rail.
How many circuits can a multi-level terminal block accommodate?
A standard double-level (two-level) terminal block accommodates two independent circuits — one per level. Three-level and four-level variants exist for even higher density. Each level is electrically isolated from adjacent levels by the internal partition.
Are the levels of a multi-level terminal block electrically connected?
No — the upper and lower levels of a multi-level terminal block are electrically independent by default. Internal bridging clips or jumper wires can be used to intentionally connect the levels if required for a specific circuit function.
What IEC standard covers multi-level terminal blocks?
Multi-level terminal blocks are governed by IEC 60947-7-1 (terminal blocks for copper conductors in low-voltage switchgear and controlgear). Performance requirements including voltage rating, current capacity, and inter-level insulation apply to both single-level and multi-level types.
What is the difference between a multi-level terminal block and a standard feed-through terminal?
A standard feed-through terminal block provides one connection level (connecting two wires through). A multi-level terminal block stacks two or more independent connection levels in one housing, allowing two separate circuits to be terminated in the same physical terminal position on the DIN rail.
What current can a multi-level terminal block carry?
Multi-level terminal blocks typically carry 16 A to 32 A per level at up to 630 V AC/DC, matching the ratings of standard single-level feed-through terminals of the same conductor capacity. Each level's conductor entry accepts 0.2–6 mm² (IEC) or 24–10 AWG conductors.
Related symbols
- DIN Rail End Stop symbol
- Duplex Outlet symbol
- Ground / Earth symbol
- Neutral Rail symbol
- Power Rail symbol
- Terminal Block symbol
Physical breadboard, PCB, and panel mapping
No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.
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