Festive string lights and coloured bulbs: safety rules

String lights work a few weeks a year and spend the rest squashed in a box. Practical safety rules for choosing, checking, connecting and using them outdoors.

Before Novruz, New Year or a family celebration, string lights come out of their box, get untangled in a hurry and are often plugged in without any check. Yet these products spend most of the year crushed together, sometimes in a damp basement. Cables get squashed, insulation cracks, lamp sockets work loose. A few simple rules are enough to make sure festive lighting does not end in a short circuit or a fire.

First check after unpacking

Before plugging the set in, run it through your hands along its full length. Look for:

• cable with cut or crushed insulation, or with copper showing;
• melted, deformed or blackened lamp sockets;
• a cracked plug or a loose controller housing;
• sections stuck together that look as if they have overheated.

If you find any of these, patching the set with insulating tape is pointless. For a low-cost decorative product, buying a new one is both cheap and safe.

It is easiest to check on a stable surface in a room with no flammable clutter. The first time you switch the set on, stay nearby for a few minutes and feel whether the cable or controller is getting warm.

Indoor or outdoor?

The packaging states where a set may be used. A product rated for indoor use only must not be hung on a balcony, in the yard or on the outside of a window: dew and rain get into the joints.

Outdoor sets have IP44 or higher protection, rubber or heavy PVC cable and sealed connectors. Many of them convert mains voltage in a separate transformer unit so that the string itself runs at safety extra-low voltage. In that case, the transformer unit itself must stay dry, for example indoors or in a protected enclosure.

The outdoor circuit should be protected by an RCD, which detects leakage current when a cable is wet or damaged and disconnects the supply.

How many sets can be linked

Some sets have a socket at the end for connecting the next one. That is handy but not unlimited. The first set's cable carries the current for every set after it. The manufacturer states on the box the maximum number of sets or the total power that can be linked. Going beyond it overheats the first set's cable and plug.

The same goes for extension leads. If you use a cable reel, unwind it completely: a coiled cable cannot shed heat and warms up even at moderate load. A chain of a multi-plug adaptor feeding an extension lead feeding another adaptor is one of the most common mistakes.

Hanging and fixing

• Do not fix the cable with nails, staples or metal clips: a pin can pierce the insulation. Use plastic hooks, adhesive clips or soft ties.
• Do not bury the lights in curtains, dry branches or paper decorations. LED strings run cool, but a damaged section or the controller can get hot.
• Cable passing through a door or window frame must not be trapped. Closing the window crushes it and slowly cuts the insulation.
• Outdoors, keep the cable out of puddles, footpaths and driveways.
• Do not leave loops hanging within reach of children and pets; cats and dogs may chew them.

Do not leave them unattended

Switching the lights off when you go out or go to bed is the simplest and most effective rule. A plug-in timer or a controller with a timer helps you remember. A set left on all night wastes energy and adds risk during hours when nobody is around to notice a problem.

When unplugging, pull the plug body, not the cable. When packing the lights away, do not wind them tightly; loop them loosely around a piece of card or a spare reel. A set stored in a dry box brings fewer surprises next season.

A note on coloured bulbs

Festive light is not only about strings. Coloured LED bulbs that screw into an ordinary holder are a convenient choice for cafés, yards and home decoration, because they need no extra cables or controllers. The same rules apply: outdoors only in a protected fitting, with a dry and firm holder. Coloured LED bulbs like these are also part of the Zəfər İşığı line.