- 1 THE heating element of electric fires for domestic use are of two main types, (a) those in which the wire is in the form of an open spiral laid in the grooves of a fireclay former, and (b) those having the wire tightly wound on a porcelain rod of relatively small diameter. The latter type is used in conjunction with a highly-polished parabolic reflector and is very efficient so long as the reflector is kept clean and polished. The fires with the open spiral type of element, though less modern, are still very popular, probably on account of their cheapness and easy maintenance. New spirals can be obtained from the electrical dealer in various wattage and voltage ranges and may be fitted at home with very little trouble. Fitting a New Spiral
- 2 Temporary Repair
- 3 Reflector Type Fires
- 4 Care of the Reflector
- 5 Cords and Plugs
THE heating element of electric fires for domestic use are of two main types, (a) those in which the wire is in the form of an open spiral laid in the grooves of a fireclay former, and (b) those having the wire tightly wound on a porcelain rod of relatively small diameter. The latter type is used in conjunction with a highly-polished parabolic reflector and is very efficient so long as the reflector is kept clean and polished. The fires with the open spiral type of element, though less modern, are still very popular, probably on account of their cheapness and easy maintenance. New spirals can be obtained from the electrical dealer in various wattage and voltage ranges and may be fitted at home with very little trouble. Fitting a New Spiral
In most cases it will be necessary to remove some kind of cover from the back of the fire so as to gain access to the screws and nuts that serve as terminals for the ends of the spiral and as connections for the mains leads. The screws and nuts will usually be found to be rusty and the application of a few drops of thin machine oil will make removal easier. To insure correct reassembly, note the positions of washers and wires. See Figs. 1 and4.
The new spiral as purchased will be in the form of a closely-coiled spring some eight or ten inches long. This must be evenly stretched to the length required to fill the grooves of the fireclay element bar. Measure the exact length.
It is a good plan to lay a length of string in the grooves to find the exact length to which the spiral needs to be stretched. Having cut the string to the required length, get an assistant to hold one end of the string together with one end of the spiral, and, taking the free end of the spiral, pull it gently until it reaches the other end of the string. Do not overdo the stretching; it is better to have it too short than too long. Now secure one end with the screw and nut provided, and carefully work the spiral into the grooves and secure the other end in the same way. When replacing the mains connections see that the wires are clean and intact and that the insulation is in good condition. When a switch is embodied, check over all nuts and screws for tightness.
It is not advisable to attempt to prolong the life of a broken spiral by joining together the broken ends, but an emergency may arise where some such expedient is desirable. If this should happen, do not fall into the common error of twisting the ends together, but proceed as follows. Cut a small rectangle of tin (un-painted or with the paint removed) about ?in. long by j-in. Wide. Bend this into the form of a letter S. Insert the ends of the broken wire, one in each bend of the S, and flatten the tin between the jaws of a pair of pliers. It is important that the ends be made clean and bright with a piece of emery paper before making the join. This is because the high temperature to which the wire is raised produces a coating of oxide, a bad conductor of electricity. This oxide must be removed to ensure good electrical contact. A join made in this way is kept cool by the tin, thus preventing the formation of fresh oxide. Apart from electrical contact it also has greater mechanical strength and neater appearance than twisted wires.
Reflector Type Fires
These fires have elements wound on a porcelain rod and are less subject to a burn-out than are the open spiral elements. Accidental damage may occur, resulting in a broken rod, in which case a complete new element may be obtained and fitted. The rod is held between two clips either by spring pressure or by a terminal nut at each end and the method of replacement is simple and obvious. So simple is it that the job is likely to be attempted without taking the precaution of first switching off the current. In all such jobs, however simple, it is always wise first to switch off the current and then to remove the plug, thus making sure that it is absolutely impossible either to get a shock or blow a fuse.
Care of the Reflector
The efficiency of the reflector type of fire is derived chiefly from the reflector. This is scientifically designed by the makers and sent out With a highly-polished finish. If the high polish on the surface of the reflector is allowed to deteriorate, the reflector will not give a thorough radiation of heat. Frequent polishing is not necessary but an occasional rub over with methylated spirits and a chamois leather is sufficient to counteract the effects of alternate heat and atmospheric moisture. Harsh abrasive polishing compounds should be avoided. The operation of polishing will be greatly facilitated by removing the elements first.
Cords and Plugs
Fires that are frequently transferred from room to room are liable to develop plug trouble. Most people know that it is bad practice to pull the plug out of its socket by tugging. This practice is often persisted in despite knowledge of the con-sequences; broken wires, damaged plugs and loosened sockets. The cap of the plug should be removed by unscrewing the countersunk screws from the underside. It may be found that one of the wires has come loose from its pin and needs to be re-secured. Another common fault is a broken wire within the insulation at the point where the flex enters. The plug. This fault in its early stages may appear intermittently and give rise to burning of the rubber covering due to sparking. The remedy is to make a clean cut right through the cord and strip back the braiding for about 2 in. from the end. Then take each lead and strip off the rubber insulation, leaving about 1 in. of the wires bare. Secure the wires to their appropriate pins. In the case of three-core flex and three-pin plugs it is important that the earth lead be connected to the earth pin. The earth pin is always the largest of the three, and the earth lead is always the one covered with brown insulation. The two other leads carry the current and are usually covered in red and white (or black) respectively. These can be connected to the two current carrying pins without reference to colour. Before replacing the cap, the loose ends of the outer braiding should be trimmed and the flex bound with twine to give a neat finish. Insulating tape may be used instead of twine but is apt to come loose when the adhesive dries out.