Installation Tips


RUNNING CABLES.

For the low voltage Automation/AV/Communications/Data cabling I would always use conduit, at least between the wall box and the floor/ceiling void. That way if you need to add/replace cables they can simply be pulled in through the conduit rather than having to chase out the walls again. I would also use 47mm deep boxes rather than the standard 16mm switch or 25/35mm socket boxes to give extra wiring space.

Wherever possible try to arrange for the wiring runs to drop from the box to floor level rather than rise from wallbox to ceiling level. The reason for this is that if you look around your room at where the power points are located you probably can't see most of them as they are hidden by furniture, but look at the wall above them and in most houses the wall area will most likely be free from obstruction above the 3-4 foot mark. No matter how hard you try it will be extremely difficult to hide the scar from chasing out the wall. Also from a typical socket to floor level is usually less than 18 inches whereas socket to ceiling is likely to be around 7 feet! Obviously if your house has concrete floors you have no choice in the matter but I will ensure my next home has wooden floors with sufficient space below.

To carry the cables between the rooms and the wiring closet I plan to construct a cable tray from 2x1 battening and 6mm plywood. This can be fixed just below the joists on the ground floor, possibly in the hallway as this would make it very easy to install aditional cables when required. Conduit from wall boxes to cabletray and a single floorboard to be lifted for access to cabletray below. For the upstairs I again plan to use the hallway by lowering the ceiling by an inch with battens in the opposite direction to the joists. This will give ample space for cables without having to weaken any of the josts with large cutouts.

Where it is necessary to drill through joists, the hole should be as near to the center as possible to minimise the weakening effect of the hole and to provide maximum protection to the cables from nails and screws. Where a number of cables need to pass through the joist it is better to cut a narrow slot along the joist (NOT ACROSS) i.e. 1/2 inch by 2 inches rather that a 1 1/2 inch hole as this will weaken the joist less.

Where cables need to go from one floor to another, try to find a closet to put the riser in. This will give plenty of space for all your cables, easy access and the minimum of disruption to the decor.

When installing cables in conduit an electricians wiring snake is a great tool to have. These are quite inexpensive to buy or you can use a piece of stiff wire for short runs of 10-12 feet. Wherever possible try to snake downhill as gravity will assist in the smooth flow of the snake.

Try to pull in all the cables at the same time (preferably with an assistant to feed the cables from the other end) as this will minimise the friction between cables and conduit. If you have to add a cable at a later date, pull it in slowly and steadily. If you use rapid jerky movements the cable you are pulling in will cut its way into the other cables where it rests on them. The damage may not be apparent immediately but could subsequently lead to a failure.

FITTING THE BOXES

Unfortunately the standard British method of house construction means your walls are probably made of brick or breezeblock. Fitting boxes to these types of walls is plain hard work. The usual method of cutting out a box is to drill around the outline of the box with a masonary drill and then use a cold chisel and hammer to remove the unwanted area of brick/block. An alternative is to use a disc cutter to cut the outline and then chisel out the centre. If you are fitting several boxes adjacent to each other, cut one large hole rather than individual ones. The reason for this is that in my experience the piece of brick/block you want to leave usually pops out anyway!

To ensure that multiple boxes line up perfectly I plan to pop rivet the boxes to either a metal plate or some angle aluminium. This will simplify the fixing of multiple boxes and ensure earth continuity for the low voltage boxes. Once the whole assembly has been fixed in place with the required number of conduits, the hole around the boxes can be filled with cement and finished with plaster. After the building type work is finished the cables can be installed with no risk of damage.

If you are "fortunate" enough to live in a house with drylined walls you have a different set of problems. Cutting out the boxes is easily achieved with a modelling knife but you require a different type of box designed for mounting in plasterboard. Getting the cables to and from the boxes can also be more difficult. Chasing out the walls is not an option as it is impossible to repair the surface. The whole sheet of plasterboard would have to be replaced. Cables need to be fed between the plasterboard and the wall behind it although this space is usually filled with fibreglass insulation. A wiring snake is useless in this situation but a small (12mm) diameter piece of conduit is usually strong enough and flexible enough to be pushed through to the cutout. This can then be used to pull a drawrope through. The only obstacle to this could be reinforcing studs partway up the wall. An inexpensive gadget called a "Stud Finder" available from DIY stores can be used to detect these studs. It works by sensing the varying density of the wall and lighting a row of LED's as the wall gets thicker. Pick an area of the wall where you know there aren't any studs and then scan the area you plan to pull the cables through. If any studs are obstructing the route they will show up on the LED's. (Also extremely useful for putting up shelves when you WANT to hit the studs)

CONCEALING AND DISGUISING CABLES.

Sometimes there is no alternative to running a cable where it will be seen. There are many ways of "hiding" these cables. Several of the DIY stores sell a skirting board which is a clip on plastic cover which conceals the cables run around the base of the room. You can make your own version by removing the existing skirting board and fixing two battens for the top and bottom of the skirting board leaving a channel for the cables down the centre. Fix a thin plywood cover to the battens and add a decorative moulding along the top edge. Once painted it will look like normal skirting board.
For cables run at high level, methods of concealment include running the cable along the top of the picture rail if you have an older style decor. Alternatively you could run the cables just below the ceiling and then fit plaster coving to enhance the decor and hide the cables.

Try to avoid running cables along the top of skirting boards and around the outside of door architrave as they are always visible and make decorating (especially with wallpaper) much more difficult. If you have painted skirting/architrave with a multi grooved profile then small diameter cables can be fixed into the grooves using "hot melt" glue and once painted over will simply disappear. Obviously this is not an option if the woodwork is stained or varnished.

To get cables from floor to ceiling level, pick a corner of the room which is not a focal point and fix a piece of plastic trunking. Once painted or wallpapered over it will be difficult to see without looking for it. If you have to use two pieces of trunking to reach the ceiling e.g 6 feet + 2 feet, then stagger the joint between lid and base. This ensures that the trunking remains perfectly aligned and make it less noticable. Even if you only need to go part way up the wall, take the trunking all the way up as this will be less noticeable than a piece which stops abruptly.

Small cables can also be concealed around the edge of the carpet between the carpet gripper and the skirting board but make sure that nothing can pierce the cable.
DO NOT DO THIS WITH MAINS VOLTAGE CABLES AND NEVER RUN CABLES ACROSS DOORWAYS OR ANY OTHER AREAS WHERE PEOPLE WILL TREAD
The only exception to this is cable which is specifically designed for under carpet use.
If you have to run a number of cables around the room then trunking can be used to follow architectural features like skirting boards and door frames. When painted it can be made to look like a wider version of what existed previously.


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This page last updated : 5th October 2000