In this tutorial we will design a three phase domestic installation. The installation consists of three distribution circuits, the Main Distribution Board and two sub distribution boards. The Main Distribution Board is located at the ground floor and feeds a sub distribution board to the basement and another to the floor level. The basic information required for the design are the Main Supply characteristics and the final circuits per distribution board. These are presented below:


Main supply characteristics:

Type: Three phase - Public supply

Voltage: 400V/230V, 50Hz

Earthing system: TN-C-S

Source rating: 500kVA with source impedance Z: 6%

Supply cable up to the origin of the installation:

  • Up to the building: Al - Multicore XLPE 90oC armoured, length: 20m, cross sectional area: 16mm2, installed underground
  • Up to the meter: Al - Multicore XLPE 90oC armoured, length: 10m, cross sectional area: 16mm2, installed on a surface



Distribution circuits:


Name

Supplied from

Phase

Cable length (m)

Cable type and installation method

Main:  MDB

Main supply

Three phase

5

Cu - Multicore XLPE 90oC armoured, in underground single way ducts

Basement DB-G

MDB

Single phase

10

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Floor level DB-F

MDB

Single phase

10

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall


Main Distribution Board - MDB:


load kind

Installation points

Cable length (m)

Cable type and installation method

Cooker

1

15

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Dish washer

1

10

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Dryer

1

10

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Fridge

1

10

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Air conditioning 1

1

20

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Air conditioning 2

1

20

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Sockets ring

25

45

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Lights 1

15

30

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Lights 2

15

25

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall



Basement distribution board- DB-G:


load kind

Installation points

Cable length (m)

Cable type and installation method

Fridge

1

10

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Air conditioning

1

20

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Sockets ring

15

30

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Lights 1

10

25

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall

Lights 2

15

30

Cu - Single Core PVC 70oC non-armoured, in conduit in a wall


Floor level distribution board- DB-F:


load kind

Installation points

Cable length (m)

Cable type and installation method

Air conditioning 1

1

15

Single Core PVC 70oC non-armoured, in conduit in a wall

Air conditioning 2

1

15

Single Core PVC 70oC non-armoured, in conduit in a wall

Sockets ring

15

30

Single Core PVC 70oC non-armoured, in conduit in a wall

Lights 1

10

25

Single Core PVC 70oC non-armoured, in conduit in a wall