No_6_December__1938_and_January__1939 — Page 25

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UNDER FLOOR METAL DUCT SYSTEM FOR ELECTRICAL

INSTALLATIONS

The planning and carrying out of the electrical in- stallation in a modern building calls for the most careful consideration in order to cater adequately for future requirements.

It is seldom possible to fix the position and require- ments of each office, workship, flat, etc., until furniture and partition plans are available, and these cannot be obtained until construction is complete. It is, therefore, necessary to install a system of wiring which will be flexible in that extensions for such things as lighting, heating, telephones, fire alarms, pilot lighting and light machinery can be quickly and easily made afterwards without inconvenience. The system needs to be simple to install and mechanically strong enough to withstand the rough treatment inevitable during erection.

To meet this need The General Electric Co., Ltd. of England, Magnet House, Kingsway, London, W.C.2, has marketed its Under Floor Metal Duet System, and this has proved itself fully equal to the demands made upon it.

It has been installed in some of the most important public buildings recently erected in London and the pro- vinces. Moreover, it complies fully with B.S.S. No. 774, 1938.

Duct fittings have been designed for simple erection, with complete rigidity, and overall dimensions have been kept, as small as possible to render the system suitable for situations where the minimum depths of screeding and floor fill are used.

Earth continuity has received primary consideration and is ensured by joining together each length of duct by malleable iron sockets into which the ducts are butted and fixed with steel cottor pins which, when driven home, make a metal to metal joint and give effective bonding under all conditions. The same principle is adopted with the connections to the junction boxes, and other acces- sories.

The duct employed is made in a standard length of 15 feet of 2" x 11⁄2" heavy gauge steel, and if required, holes 14" diameter are provided at predetermined inter-

vals for connecting various fittings to enable floor con- nections in the form of standpipes, etc., to be attached.

Junction boxes are supplied in cast iron and equipped with floor traps made from a special hard wearing alloy, and are constructed with machined edges and fillets. They have tapped holes for inserting special lifting keys to facilitate their removal for inspection purposes.

Two sizes of junction box are made, (A) three holes on each or any side, and (B) two holes on each or any side, or alternatively they can be supplied undrilled for contractors to drill as required. The ducts are joined to the boxes bn adaptors of malleable iron, and a small degree of flexibility allows for any slight inequality in alignment due to the rough floor surface.

Intersectors for both 2-way and 3-way boxes separ- ate the high and low tension services and accord with the I.E. Regulations in every respect. They are bonded to the boxes by special earthing screws.

When outlets are required in the duct, a hole of 14" diameter is made, which allows any of the adaptors and standpipes to be connected without any tapping or cutting to be done. If the holes are not required immediately, they are closed with a pressed steel cover which snaps in position and is sealed with compound until needed.

Conduits can be run off the ducts by means of a special type of conduit box which is fixed to the outlet hole by a malleable clip, and is supplied in the standard small B.S. size in all the usual types.

Small traps are made for placing over openings covering unused outlets and conduit boxes.

This system enables the architect and consultant to deal with the electrical scheme at the outset of the job. Moreover, it ensures complete freedom for G.P.O. services and extensions as usually a separate duct can be allocated to them.

Further particulars may be obtained from the General Electric Co., of China Ltd., 2 Queen's Building, Hongkong, who represent the General Electric Co., Ltd. in the Far East.

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