I welcome you, dear guests!
On parallel connection of veins of power cable
If you examine the inside and Rules for Electrical Installation (PUE), we do not find the answer to this question. Besides, we do not have any technical standards that would allow or forbid this type of connection. Therefore, this method does not standardized documented, but there are other features ...
It turns out that this is not prohibited, and therefore permitted?
In accordance with the requirements of Section 1, Chapter № 1.3. Regulations for Electrical Installation - Selection section of each conductor must be made on the heating and acceptable long-currents. If the selected section satisfies a predetermined condition, the connection takes place.
So we see that RB does not care about this issue, and rules do not prohibit the parallel connection of two (or more) conductors, most importantly, that conditions for permissible currents. As well, and Ohm's law allows us to calculate the attributable burden on each cable in the presence of power equipment at the other end.
But there is only one real danger of such an installation as a failure of one of the cores, and the reasons multiple: it can be scorching contact one of the conductors, oxidation or poor connection terminals.
In this case, the entire burden will fall on the rest of mine, and Kirchhoff's law, the current second conductor will increase and increase heating. Although this option can be eliminated by selecting for each of your living-breaker, but with so that the switches are dependent on each other and are both shut down at once in the reaction at any of them.
If we consider all the theoretical concepts and perfect fitting, when safe ban connections and can not be. The length is, the same cross section - and hence the resistivity of both cores is approximately equal, respectively, and the value of the currents flowing in these veins is equal.
So the conclusion is that for the correct operation of such a scheme is essential to organize a good contact and avoid even small transitional resistance in places compounds, or in the presence of load current through the veins will be distributed unevenly, whereby this may lead to overheating of one of the cores and disastrous result.
About the interchangeability of sections
As for the section, then if you believe the Table 1.3.4 PUE, take the cable 2x2.5, the allowable continuous current of which - 25 A per strand. Under this value 25A for replacement of veins 2.5 mm² suitable embodiments as a (2x1) of the two conductors 1 mm² (15 + 15 = 30 A), and so (2x1.5) two cores of 1.5 square .mm (18 + 18 = 36 A), etc.
"It is possible, but it is better do not need"
But I would like again to warn that despite the fact that this method of connection is not prohibited, it is better not to put such experiments and acquire the desired ONE REQUIRED section of the cable, since you will not always be able to constantly monitor the status of contacts and wires!
Good luck to you, take care of yourself and loved ones!
1. Spike wires without soldering iron! working method.
2. How fast do twist the wires? Fixture in 5 minutes!
3. Shut-off ball valve is broken under pressure? Walkthrough for replacement.