Introductory devices, switchboards, distribution points, group shields

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 7. Electrical equipment of special installations

Electrical installations of residential, public, administrative and household buildings. Introductory devices, switchboards, distribution points, group shields

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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7.1.22. At the entrance to the building, a VU or ASU should be installed. One or more VU or ASU can be installed in the building.

If there are several economically isolated consumers in the building, it is recommended to install an independent VU or ASU for each of them.

From the ASU, it is also allowed to supply consumers located in other buildings, provided that these consumers are functionally connected.

With branches from overhead lines with a rated current of up to 25 A, the VU or VRU may not be installed at the inputs to the building if the distance from the branch to the group shield, which in this case performs the functions of the VU, is not more than 3 m. This section of the network must be carried out by a flexible copper cable with with a core cross section of at least 4 mm2, flame retardant, laid in a steel pipe, while the requirements for ensuring a reliable contact connection with the branch wires must be met.

For air inlet, surge suppressors must be installed.

7.1.23. It is not allowed to install additional cable boxes before entering buildings to separate the service area of external supply networks and networks inside the building. Such separation should be carried out in the ASU or MSB.

7.1.24. VU, VRU, MSB must have protection devices at all inputs of supply lines and at all outgoing lines.

7.1.25. At the input of the supply lines to the VU, ASU, MSB, control devices must be installed. On outgoing lines, control devices can be installed either on each line, or be common to several lines.

The circuit breaker should be considered as a protection and control device.

7.1.26. Control devices, regardless of their presence at the beginning of the supply line, must be installed at the inputs of supply lines in retail premises, utilities, administrative premises, etc., as well as in consumer premises that are administratively and economically separated.

7.1.27. The floor shield must be installed at a distance of no more than 3 m along the length of the electrical wiring from the supply riser, taking into account the requirements of Ch. 3.1.

7.1.28. VU, VRU, MSB, as a rule, should be installed in switchboard rooms accessible only to service personnel. In areas prone to flooding, they should be installed above the flood level.

VU, ASU, MSB can be located in premises allocated in operated dry basements, provided that these premises are accessible to service personnel and are separated from other premises by partitions with a fire resistance limit of at least 0,75 hours.

When placing VU, ASU, MSB, distribution points and group shields outside the switchboard rooms, they should be installed in places convenient and accessible for maintenance, in cabinets with a shell protection degree of at least IP31.

The distance from pipelines (water supply, heating, sewerage, internal drains), gas pipelines and gas meters to the installation site must be at least 1 m.

7.1.29. Switchboard rooms, as well as VU, ASU, MSB, are not allowed to be located under sanitary facilities, bathrooms, showers, kitchens (except for apartment kitchens), sinks, washing and steam rooms of baths and other premises associated with wet technological processes, except when special measures have been taken for reliable waterproofing, preventing moisture from entering the premises where switchgears are installed.

It is not recommended to lay pipelines (water supply, heating) through electrical switchboard rooms.

Pipelines (water supply, heating), ventilation and other ducts laid through switchboard rooms should not have branches within the room (with the exception of a branch to the heater of the switchboard room itself), as well as hatches, valves, flanges, valves, etc.

Laying gas and pipelines with flammable liquids, sewers and internal drains through these premises is not allowed.

Electrical room doors must open outwards.

7.1.30. Premises in which ASU, MSB are installed must have natural ventilation and electric lighting. The room temperature should not be lower than +5 oC.

7.1.31. Electrical circuits within the VU, ASU, MSB, distribution points, group shields should be carried out with wires with copper conductors.

See other articles Section Rules for the installation of electrical installations (PUE).

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