Surface Mounted Installation
Surface mounted installations are used in various situations such as:-
· Extensions to an existing flush installation when interference with existing walls, floors or decor is not acceptable to the client.
· Rewiring of existing installations, again where walls, floors or decor cannot be interfered with or where cost is an important factor.
· Wiring of portable or prefabricated buildings.
A surface mounted installation in domestic / commercial situations normally involves the use of conduit or trunking. It is not unusual to see a combination of flush and surface work together, cables being concealed where possible and mounted on the surface where concealment is not possible.
PVC / PVC cables are normally used in surface mounted installations, as they can be installed directly on a surface, in a building void, in conduit, or in trunking.
Surface type boxes are used rather than flush types. Switches, sockets etc. are the same for both surface and flush types of installation.
Surface switch boxes are about 20mm deep and white in colour, to match the type of switch used. The boxes have knock-outs for cable entry on all four sides and also in the base. These knockouts should be carefully cut out using a junior hacksaw, to suit the cable being installed. The boxes may be fixed directly to a surface using countersunk woodscrews placed through slotted holes for easy alignment, or directly to a round flush mounted conduit box.
Figure 3 illustrates a single surface mounted box, which can accommodate either 1, 2 or 3 gang switches. The double surface mounted box, shown in Figure 4, can accommodate either 4 or 6 gang switches.
