Monday, November 29th, 2021

Features of connecting hobs to the mains

The need for a separate power cable from the distribution board of the apartment (PD) to the electric hob gave rise to a number of connection problems. In homes, the supply voltage is one-, two-, and three-phase. We will show you how to connect the PDP to the panel terminal block.

Terminal markings
Typically, electric hobs have six terminals, but a six-core cable is never used. Most often, three-core – in old houses, five-core – in new ones. Rarely four-core. The number of veins depends on the number of phases in the distribution board of the apartment. international news

 

The figure shows a six-terminal box where:A three-wire cable has been pulled from the switchboard or from the socket. The socket is an intermediate link. To put it or not, see here . It does not affect the docking of the switchboard with the terminal block. There are boxes with fewer terminals, but the principle of joining them with the cable remains the same.

This example is an extreme case. Less than three wires should not leave the distribution board. The hob does not have more than six terminals. There are also options when, on the contrary, there are more cores in the cable than the terminals at the plate. The connection principle is simple: phase – zero – ground are the necessary attributes for the correct functioning of any panel.

On the bottom cover of the product, an instruction-diagram for connecting the surface terminals to a one-, two- and three-phase network is glued.

 

1N ~, 2N ~, 3N ~ – number of connection phases.

If you have six terminals and three phases, then you need to put jumpers, as shown in red in the figure. Jumpers are usually supplied with the kit.

 

The jumpers are necessary for the hob to work properly. You need to fasten it securely, with effort, but do not overdo it. Remember that plastic is fragile and the screws are small.

Color coding of wires
Makes installation work much easier. The colors of the wires are regulated by the PES (Electrical Installation Rules) of the Russian Federation and European standards.

Grounding is yellow-green, sometimes pure yellow or green. Designation on the diagram – PE
Neutral or zero – blue or light blue. Designation – N
Phase – brown, black, white, gray, red, purple, orange, pink, turquoise

The PEN wire is a legacy grounding system in which neutral and ground are combined. This simplifies electrical work, but increases the risk of electric shock. Yellow-green (like PE) or blue like N.

Single-phase 220 V network
The most common option. Three wires depart from the RP, which come to the hob terminal block with three, four, five and six terminals. We figured out the six terminals – the picture above.

 

For a four- terminal box requiring two phases, the same principle: put a jumper between the phase terminals:

 

We connect the wires from the power supply of the house, respectively: L1 – with the phase, N with zero, PE – grounding.

Five-terminal box . We put a jumper between the phase and between the zero terminals:

 

As in the previous example, we connect L1 – to the phase, N to zero, PE – to ground.

Three-terminal box. The easiest option, because there are no options. Phase to phase, PE to PE, zero to zero.

Two-phase network for 220 V
In a two-phase network, a two-phase surface is connected one to one. One jumper should be placed in a three-phase panel. There is one phase in a single-phase panel. The other phase is insulated in the junction box.

 

Four wires come from the dashboard to the apartment

 

Shown is a terminal block for an Electrolux EHH56240IK induction panel . Here is the full correspondence of the cable from the distribution board and the terminal block of the plate. The power of the stove is 6.5 kW. Since two phases are used, the current through them will be half as much as one by one. Due to this, the cable can be taken with a smaller cross-section.

For a three-terminal box, one of the phases is not supplied, but isolated.

Connection with six-terminal surface

 

We see how a two-phase network can power a 380 V electric panel. A diagram with a plug is shown. But the wires are the same that go from the distribution board to the outlet.

Three-phase 380 V network
Important. All surfaces operate on a phase voltage of 220 V. The use of several phases is necessary to reduce the load on the power grid. Line voltage 380 V is not used.

 

Three-phase network and three-phase surface. One to one. The most optimal option. The cross-section of a five-core cable 2.5 mm² is suitable for plates of any power.

 

The same wires go to the plug as to the corresponding outlet from the switchboard.

Two-phase panel in a three-phase network
To connect such a panel to a three-phase network, you must not use phase L3 – the gray color of the cable core coming from the shield. This core must be insulated in the back box.

 

In the diagram, the cable goes from the difavtomat to the distribution board into the junction box. There may be an outlet instead. The four cables of the two-phase model are included in the same box or plugged into an outlet.

Some models come with a 4-wire cable pre-installed. Most often these are induction hobs for 4 burners. In this case, the induction cable is put into a box or connected in a plug, as in the picture above.

 

Single-phase panel in a three-phase network
An analogue of the previous scheme of a two-phase panel. Do not use phases L2 and L3. These two conductors must be insulated in the junction box.

Power cable selection
According to the PUE, clause 7.1.34, the cable must be copper. Three-core if you have single-phase power at home (picture above). Five-core for three-phase.

Cable cross-section – cross-sectional area of ​​1 copper conductor in mm².

The choice of cable is described in detail here . Let’s add a pivot table:For a two-phase network, the parameters of the cable cores and the difavtomat coincide with the parameters of a single-phase network. Although logically, the load on the core in a two-phase network is two times less than that in a single-phase network. But, let’s look at the connection diagram of a three-phase surface to a two-phase network, taken from here

 

We see that the two phases of the panel 1 and 2 are connected by a jumper. That is, two burners will be powered from one phase of a two-phase network. Therefore, for surfaces with a power of more than 3.5 kW, a thicker cable is needed. In addition, two-phase networks are rare in homes. They were installed long ago in the 90s. There is little information about their reliability. It is better not to risk it and equate them to a single-phase network. Then you can sleep peacefully!

Small FAQ
Why is the zero of a three-phase network not overloaded, although current flows through it from three phases?

If the phases are loaded symmetrically, then nothing flows through the zero core. Because these currents are 120 ° out of phase with respect to each other. It is not about the addition of the absolute values ​​of the currents, but about the vector (algebraic) sum.

The voltage is created by a three-phase generator – three identical windings located at an angle of 120 ° to each other.

Resulting voltage:

The main thing is to protect a person from electric shock in the event of a phase breakdown on the housing of a household appliance.

In Soviet houses, two wires went from the switchboard to the apartment (and are now going): phase, zero. That is, there is no grounding conductor. Its role is played by a working zero – N. If this core (zero) accidentally breaks (which happens very rarely) in the apartment or in the dashboard (at the entrance), then the 220 V phase will fall into all the sockets of the apartment and the devices connected to them. There will be a danger of a shock with a voltage of 220 V. This will happen if a person touches the punctured case with one hand, and with the other or his foot touches a surface with a natural ground (pipes, sink, the floor is wet and not very).

Therefore, in modern houses there are no less than three lived from the dashboard to the apartment. One core – grounding (protective zero, PE). On the protective zero, the current flows only in case of breakdown to the device case. The current flows along the working zero during the operation of the devices.

 

Some electricians, using euro sockets (for which three wires are needed), connect the ground to a working zero. That is, zero in “khrushchob” works for them, as a worker and as grounding. This is dangerous, since in the event of a break in the core of the working zero, all zeroed cases will be energized at 220 V, regardless of the technical condition of the household appliance – it can shock from a new refrigerator or a new washing machine. This “trick” is strictly prohibited.

Do you need an outlet?

The more connections, the less reliable the circuit. That is, without a socket – less heating of the line due to a decrease in active resistance, higher safety. But in this case, to disconnect the surface from the network, you need to leave the apartment. Plus, hang a sign in the dashboard: “do not turn on!”

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