Distribution Boards and Terminal Distribution Boxes

By where they sit on the low-voltage chain. The main distribution line-up on the transformer low-voltage side uses GGD at a 630–4000 A horizontal busbar; workshop or floor power distribution uses XL-21 at 630–1000 A busbar; sub-distribution and motor control use MNS-E at 63–630 A busbar, as either a wall box or a floor-standing box; terminal circuits use PZ30 at 6–100 A across 6 to 48 ways. Separate metering uses PML. Outdoor positions take JXF or XLW instead.

No. Withdrawable low-voltage switchgear runs a 6300 A horizontal busbar in a 2200 mm cubicle and its functional units are interchangeable drawers; MNS-E is a distribution board or box with a 63–630 A busbar, built as a wall box or a floor-standing box, in distribution, motor control and dual-supply duties. The two are an order of magnitude apart: main distribution line-ups take the former, sub-distribution and terminal control the latter.

No, and the difference matters. GGD, XL-21 and MNS-E work to GB 7251.1 and IEC 60439-1 at overvoltage category IV; the PZ30 product overview cites GB 7251 part three and IEC 60439-3 at overvoltage category III. Part three covers boards intended to be operated by ordinary persons — which is exactly the level a terminal consumer unit occupies in housing, offices and commercial premises, switched by people who are not electrically skilled.

PML at IP20 and PZ30 at IP30 belong only in a dry, clean indoor distribution room; GGD is IP30 as standard and IP40 on special request; XL-21 offers IP30, IP40, IP43 and IP54; MNS-E leaves the works at IP30 as standard and can be selected between IP20 and IP65 to suit the environment. Outdoor positions go straight to JXF at IP65 or XLW at IP54, both of which can take a stainless steel enclosure for corrosive settings.

PML comes in cubicle widths of 500, 600, 800 and 1000 mm at a depth of 600 mm. MNS-E wall boxes run 400–900 mm wide, 550–1000 mm high and 175–300 mm deep; floor boxes run 400/600/1000 mm wide, 1600/1800/2000 mm high and 350/400/450/500 mm deep. Dimensions for GGD, XL-21, PZ30 and the outdoor enclosures follow the number of circuits and the cable entry arrangement, settled at drawing approval.

This family is designed for indoor use: altitude not above 2000 m; ambient air not above +40 °C and not below −5 °C, with the 24 h mean not above +35 °C; relative humidity not above 50 % at a maximum temperature of +40 °C, higher humidity being permitted at lower temperatures, for example 90 % at +20 °C; inclination to the vertical not more than 5°; and a site free of fire and explosion hazard, of conductive or insulation-damaging dust, of chemical corrosion and of severe vibration. Transport and storage run −25 °C to +35 °C, and not above +70 °C for short periods of up to 24 h. Outdoor positions use JXF or XLW instead.

Yes. The boards are supplied as equipment, while the enclosure, panel arrangement, auxiliary systems and interface integration are supplied by the prefabricated power module line, with the boards delivered as equipment inside the module. Where medium and low voltage share one module it is handled as a primary-equipment module, with line-up sections, busbar bridges and in-module interfaces detailed together and the delivery boundary settled once at contract stage.

Four things at minimum: the low-voltage single-line diagram or circuit schedule; the incoming capacity and transformer parameters; the rated current and short-circuit level at each level; and whether the installation is an indoor distribution room or an outdoor position. To quote to contract level, add the metering and protection configuration, the required degree of protection, cable entry directions and cable sizes, the control supply and communication interfaces, and the destination market standards and document list.