Terminals or twist: compare ‘for’ and ‘against’

Which contact connection should I use when installing wiring? We will measure the resistance at each connection, let’s talk about their advantages and disadvantages.

There are fierce disputes between electricians about, which wire connection is better: terminal or twist? Experts of the old school will say, that there is nothing better than a good twist, and modern electricians will beat their chests, convincing, that it is necessary to connect wires only with Wago terminals, KBM or bolted terminal blocks. Who is right? Let’s plunge into this confrontation and draw our own conclusions.

Content:

  1. What does the PUE say?
  2. Classification of wire connections.
  3. Testing of connection resistance.
  4. Twisting.
  5. Screw terminal block.
  6. PPE.
  7. Construction and installation clamps (Wago, KBM).
  8. To sum up: which connection should I choose?

What does the PUE say?

To begin with, you should contact the PUE and figure it out, what is generally acceptable for connecting wires. In PUE P2.1.21 says: ‘Connection, branching and terminating of wires and cables must be carried out by means of crimping, welding, soldering or clamping in accordance with the current instructions’. As you can see, the PUE does not say anything about, that the wires can be connected with ordinary twists. However, twists have been so long and so closely settled in our lives, that we just can’t get around them.

Classification of wire connections

The following products are most often used for connecting cores (sleeves are not considered in this context):

  • Twisting.
  • Screw terminal block.
  • PPE.
  • Self-locking terminal block (Wago, Weidmuller et al.).
  • Construction and installation terminal KBM.

Each of the connecting elements has its own insulation, in addition to the usual twist, for which you will need a heat shrink or duct tape. To understand, which connector conducts the current best and, accordingly, heats up less, we need to measure its resistance.

Testing the resistance of the connections

The test was carried out using the device Micromilliohmmeter X-1A. It is designed to determine the electrical current resistance of bolt and terminal connectors.

For each connector, 2.5 mm pieces of wire were taken2

  1. Screw terminal block 40 mkOm.
  2. PPE 68 mkOM.
  3. Twisting 302 mkOm.
  4. Flat spring clamp Wago 458 mkOm.
  5. Construction and installation terminal KBM 654 mkOm.

The screw terminal block proved to be the best in the tests. The twist is the same, oddly enough, surpassed Wago and KBM. However, the resistance indicator alone is not enough to, to solve, which type of connection is better for wiring. After all, a lot depends on the contact area, and over time, the junction may become clogged with dust and dirt, which will worsen the contact. Let’s take a closer look at each type separately.

Twist

This is the most common type of connection, which can be performed without special devices and even with fingers (we do not recommend). Since the usual twist is characterized by a rather unreliable connection, then soldering or welding of an already twisted connector is additionally applied.

Advantages of twists:

  • Cheap connection
  • Large contact area
  • Maintenance-free
  • It is possible to connect single-wire and multi-wire cores

Disadvantages of twists:

  • Low moisture resistance
  • Additional isolation required
  • Aluminum and copper cannot be connected
  • High duration of the technological process
  • Additional equipment required

Twisting without soldering and welding is usually used when installing temporary buildings, which will have to be cleaned up later.

Screw terminal block

The screw terminal block is a metal tubular connector with screws, clad in a plastic case. Two wires are wound inside the terminal block and tightly clamped with screws.

Advantages of a screw terminal block:

  • Excellent contact
  • Presence of isolation
  • Inexpensive.

Disadvantages of screw terminal blocks:

  • Need for maintenance
  • Complexity of using stranded wires

Screw terminal blocks are mostly applicable for electrical switchboards, where there is always access for repair and revision.

ppe

The self-insulating clip is a regular plastic cap with a spring inside. It is enough to put two wires there and twist them with a cap. You can call it one of the types of twisting, but with the existing insulation.

Advantages of PPE:

  • Cheap connection
  • Easy installation
  • Non-combustible material
  • A large number of colors.

Disadvantages of PPE:

  • Low insulation properties
  • Wires of different metals cannot be connected

So, PPE is suitable for connecting wires in switch boxes for small current loads, for example, for the organization of lighting. For heavy loads or for connecting aluminum and copper wires, it is better to opt for terminal connectors.

Construction and installation clamps

The most popular are Wago flat-spring terminal clamps. They consist of a terminal block, pressure spring and keys. The veins are wound into the pad and pressed with the keys. The insulation is made of polyamide.

Advantages of flat-spring clamps:

  • Connecting multiple cores
  • Connection of conductors made of different metals
  • Fixation of single-wire and multi-wire cores
  • Connection speed
  • Small size.
  • Connector for indicator screwdriver.

Disadvantages of flat-spring clamps:

  • High price
  • Low quality analogues

Wago flat-spring clamps are suitable for both lighting organization, so it is for all wiring in the house. They are reliable and durable. Some of the models are reusable.

Another type of construction and installation clamps are CBM. The principle of their work is similar to Wago, with the only difference in the design. They are also cheaper than their German counterparts, which makes them very popular among domestic electricians. CBMs do not require additional equipment for installation and provide a good ‘clean’ contact.

To sum up: which connection should I choose?

Twists should be used if:

  • You are doing wiring in a temporary facility, for example, shed or outbuilding.
  • You have an inverter welding machine or a soldering iron for high-quality connection of twisted wires.
  • Want to save on components.

Terminal blocks should be used if:

  • You need to connect aluminum and copper wires, for example, in an old house or in the country, where is the aluminum wiring.
  • The speed of work is important for you, and you don’t want to waste time on welding or soldering.
  • It is necessary to ’sew’ the connected wires under drywall or plaster (does not apply to screw terminal blocks).
  • You want to have access to the contact without having to disassemble the insulation (to check for voltage in the phase).
  • Are you ready to spend money and get quality connections, which will not need to be paid attention for many years.

Read also:

  • Three-phase power supply in the house: does it make sense?
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