What Is a Twist-On Junction Box Connector? Sizes and Selection Criteria
A twist-on junction box connector is an insulated splice connector that is turned onto stripped conductor ends and clamps them together with a threaded metal insert.
A twist-on junction box connector (screw-type junction box terminal) is an insulated splice connector that is turned clockwise onto stripped conductor ends, and whose tapered threaded metal insert twists and clamps the conductors together. It is used inside junction boxes to join the conductors of lighting and socket circuits at a single point. It has no separate screw or tab; the connection is made by turning the connector itself.
How it differs from other junction box terminals
| Type | Connection | When to choose |
|---|---|---|
| Twist-on junction box connector | The connector is turned onto the conductor ends | Splices where several conductors meet at one point |
| Tabbed junction box terminal | Each conductor goes into its own entry and is clamped with a tab | Conductors of different sizes, splices to be reopened later |
| Plug-in junction box terminal | The stripped conductor is pushed into the hole | Quick, compact splices with solid conductors |
Selection criteria
- Number and size of conductors: Each size is designed to join a certain number of conductors of certain cross-sections. Check the minimum and maximum combination of conductors on the product page or the packaging.
- Size and color: KSN marks the size with the KP number, and each size has its own color: KP-1 gray, KP-2 blue, KP-3 orange, KP-4 yellow, KP-6 red. The color only identifies the size; it does not indicate a phase, neutral or earth conductor.
- Voltage and temperature: The catalog data gives 600 V and a maximum of 105 °C for the KP series. Do not exceed this limit in hot places such as a luminaire connection compartment.
- Conductor material: The catalog data has no suitability information for aluminium conductors; use the connector with copper conductors.
How to install
- Strip the conductors to the length given on the product page or the packaging.
- Hold the ends side by side, aligned.
- Place the connector over the ends and turn it clockwise until it sits tightly.
- Pull each conductor gently to check; no bare conductor should be visible below the connector.
Common mistakes
- Putting too many conductors into a small size: The insert cannot grip the conductors fully, contact stays loose and heats up.
- Stripping the conductor too long: Bare conductor remains exposed below the connector.
- Turning it the wrong way: The insert does not clamp the conductors and the splice stays loose.
- Taking the color for a conductor color: A red or blue connector does not mean phase or neutral.
- Using it instead of DIN rail terminal blocks in a panel: Ordered, numbered connections inside a panel are made with terminal blocks mounted on a DIN rail. A twist-on connector belongs inside a junction box or a luminaire connection compartment.
Related standard
- IEC 60998-2-4: Particular requirements for twist-on connecting devices, within connecting devices for low-voltage circuits for household and similar purposes; applied together with IEC 60998-1. The product names in the catalog do not state conformity with this standard.
Twist-on junction box connectors in the catalog
The Screw-Type Junction Box Terminal Blocks category has 5 active products, all from KSN and sold individually:
| Model | Color | SKU |
|---|---|---|
| KP-1 | Gray | `KSN3300` |
| KP-2 | Blue | `KSN3301` |
| KP-3 | Orange | `KSN3302` |
| KP-4 | Yellow | `KSN3303` |
| KP-6 | Red | `KSN3304` |
According to the catalog data, all are tin-plated brass with PVC insulation, rated 600 V and a maximum of 105 °C; body dimensions range from B 8.5–16.0 mm and C 6.7–13.0 mm depending on size. Other types are in the Junction Box Terminal Blocks category.
Frequently asked questions
Which size of twist-on connector should I choose?
Look at the number and cross-section of the conductors to be joined. The conductor combination each size accepts is given on the product page or the packaging; if your combination is outside it, choose the next size up or down.
Does the connector color indicate phase or neutral?
No. In the KSN KP series, the color only indicates the size. A conductor's function is shown by the color of its own insulation.
What is the difference between a twist-on connector and a tabbed junction box terminal?
A twist-on connector joins all conductors at one point by turning the connector. In a tabbed terminal, each conductor goes into its own entry and is clamped with a tab; it is easier to join conductors of different sizes and to reopen the splice later.