What Is a 1-In 2-Out Terminal Block? Uses and Selection Criteria
A 1-in 2-out terminal block is a DIN rail terminal block with one connection point on one side and two on the other, joining three conductors at the same potential.
A 1-in 2-out terminal block is a DIN rail terminal block with one connection point on one side and two on the other, joining all three points at the same potential. In a control panel it is used to distribute one supply or signal conductor to two separate loads, or to collect two conductors onto a single line. Because it does the job in one housing, it removes the need to join two standard terminal blocks with a jumper.
Types of multi-conductor DIN rail terminal blocks
| Type | Connection points | Circuit | Use |
|---|---|---|---|
| Standard terminal block | 2 (1 on each side) | Single potential | Connecting one conductor to another |
| 1-in 2-out terminal block | 3 (1 on one side, 2 on the other) | Single potential | Distributing one line to two loads, collecting two conductors |
| 2-in 2-out terminal block | 4 (2 on each side) | Single potential | Common supplies and returns with two conductors on both sides |
| Double-level terminal block | Separate points on each level | Two independent circuits in the standard type | Connecting two separate circuits in the same width where space is tight |
The words "in" and "out" only describe which side the connection points are on; the terminal block does not distinguish the direction of current.
Selection criteria
- Number of connection points: Choose by how many conductors meet at the same potential. One 1-in 2-out block is enough for three conductors, one 2-in 2-out block for four. If you need more points, join several terminal blocks with plug-in top jumpers.
- Total current: The single connection point on one side carries the sum of the currents of the two conductors on the other side. The Onka OPK models in the catalog have a rated current of 24 A, and this value applies to the whole terminal block, not to each output.
- Conductor size and type: The product name says 2.5/4 mm². Check the manufacturer's data sheet for the minimum and maximum connectable cross-section for solid, stranded and ferrule-fitted conductors, and for the stripping length.
- Connection technology: The OPK series uses push-in spring connection. Solid or ferrule-fitted conductors are inserted without tools. To insert a fine-stranded conductor without a ferrule, or to remove any conductor, press the release button with a screwdriver.
- Housing color: Color does not change the electrical ratings; it only helps tell circuits apart. Blue housings are commonly used for neutral (N) terminal blocks; choose the other colors according to the panel's color scheme.
Common mistakes
- Ignoring the total current: If the currents of the two loads add up to more than 24 A, this terminal block is not enough; you need a larger terminal block or a separate supply.
- Putting two conductors into one connection point: This terminal block exists to give each conductor its own point. If you plan to use twin ferrules, confirm that the manufacturer's data sheet allows them.
- Forcing a fine-stranded conductor in without a ferrule: The strands splay and contact suffers. Fit a ferrule, or open the clamp with the release button before inserting.
- Using a green-housing terminal block for the protective conductor: A green housing is only a marking color. The protective conductor (PE) goes to a green-yellow protective conductor terminal block (IEC 60947-7-2) that contacts the rail.
Related standards
- IEC 60947-7-1: Sets construction and test requirements for DIN rail terminal blocks for copper conductors; this product group falls within its scope.
- IEC 60445: Identification of conductors by color; blue is for neutral, green-yellow for the protective conductor.
1-in 2-out terminal blocks in the catalog
Welibaba lists 8 active 1-in 2-out terminal blocks; all are from the Onka OPK series and differ only in housing color:
| Series | Ratings | Color and SKU |
|---|---|---|
| Onka OPK 2.5/4 mm² | 24 A, 750 V | gray `1020285`, beige `1020286`, black `1020287`, blue `1020288`, brown `1020289`, red `1020290`, yellow `1020291`, green `1020292` |
Frequently asked questions
What is a 1-in 2-out terminal block used for?
It connects one conductor to two conductors, or two conductors to one, at the same potential. For example, it is used to distribute a control supply to two separate devices.
What is the difference between a 1-in 2-out terminal block and two jumpered standard terminal blocks?
The electrical result is the same: three conductors are joined at the same potential. The 1-in 2-out terminal block does this in one housing without a jumper, so there are fewer parts and less wiring work. A jumpered row, on the other hand, can be extended to as many points as needed.
What is the difference between 1-in 2-out and 2-in 2-out terminal blocks?
A 1-in 2-out terminal block has three connection points, a 2-in 2-out terminal block has four. In both, all points are at the same potential.
Can each output carry 24 A?
No. 24 A is the rated current of the whole terminal block; the conductor on the single side carries the total current of both outputs.