Basic Living Room Appliances: electric heaters

Three main types of domestic, free-standing, portable electric heaters are widely used: radiant, convector and fan heaters. Some appliances combine different heater types, such as a convector plus a radiant bar.

Radiant heaters

Heat is produced by an element that glows red-hot when power is supplied to it. The heat generated by this action is directed by a highly polished reflector through an open front protected by a metal grill. The element can be externally wound on a ceramic mount or internally mounted in a heat-resistant silica glass tube. Simple switching of the element/s is included and faults can easily be traced.

Convector heaters

Heating in these is by an open spiral/spring element supported on mica or ceramic plates at the base of the unit. No moving parts are used to distribute heat; only normal convection air current created by warm air rising from the heater.

A simple on/off switch is usually included and often a variable thermostat of the bi-metal type is used to maintain a pre-set temperature by switching the element on or off as required. A TOC is often fitted to preventoverheating.

Fan heaters

The fan heater is the most popular of all portable heaters, mainly because of its compact size and its ability to heat a large room quickly. This is done in a similar way to the hairdryer, but a much larger element is used (up to 3kW).

It may have a variable heat output — typically 700W, 1300W and 3,000W — by means of a switchable combination of elements and some have thermostats. A cold blow facility is often included for summer use; this simply allows the motor and fan to run without any of the elements in circuit.

A shaded-pole motor is normally used. Large fans or barrel fans are attached directly to the rotor to blow air over the element assembly. This creates a powerful airflow that rapidly heats (or helps cool) the room.

Problems

All three types of heaters must have the correct rated cable fitted and care should be taken, not only in repair and servicing, but in the safe use and positioning of all heating appliances.

The fan heater is more complex than the other two types of heater and may have mechanical as well as electrical problems. A safety thermostat/TOC is incorporated to switch off the element should motor failure occur.

Most heaters require three-core earthed flex, but some modern fan heaters may be double insulated and have only two-core flex fitted. Ensure the correct cable is fitted when renewing and check the rating plate to verify if the appliance is double insulated.

It is essential that all wiring and covers are refitted in their correct positions after servicing or repair. Make a note of each item and its position during stripdown.

Both convector and radiant appliances require little maintenance. Periodically, check the mains lead for damage or wear and tear along its whole length. Inspect cable sleeves and terminal block connections, making sure they are tight and no overheating is present. Regularly check the air inlet grilles on the base of a convector heater for fluff and debris and clean as necessary.

Keep the reflector on radiant heaters clean and bright, but take care when cleaning not to damage the ceramic or glass mounts of the elements. Check the radiant bar ends, making sure they are tight and a good electrical connection is being made. When cleaning or inspecting these appliances, ensure a correct earth path exists between all linked metal parts and the earth pin of the plug, unless it is a double insulated appliance.

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