OVEN-HEATING ELEMENTS. - The ovens of electric ranges are equipped with open or enclosed elements. These include the rod and coil, suspended coil, spiral-wound, or tubular types. Ovens have two heating elements. One is located in the upper part of the oven and the other in the lower part. Oven elements work off a thermostat to control heat temperature and a timing device for automatic shutoff, as shown in figure 7-6.
TROUBLESHOOTING. - In troubleshooting, start by checking to ensure that proper voltage is going to the unit; then check each element and control device. The heating element, though ruggedly constructed, might become open-circuited. That can be checked with an ohmmeter. Normal resistance is somewhat less than 100 ohms. If elements are opened, replacement is necessary.
If the heating element checks normal but the unit does not heat up, the controls should be checked. Voltage measurement is the most reliable test for a switch. When turned off, the measurement across the switch terminals should read "FULL-LINE VOLTAGE," 120 or 240 volts. When the switch is ON, the reading should be zero across the terminals. Any voltage reading across the terminal of a closed switch indicates a fault. Replacing a faulty switch involves the disconnection and replacement of many wires. A sketch or identifying tags should be used to ensure the correct relocation of the wires.
Oven thermostats control temperature and are factory-calibrated for that unit. Some units can be recalibrated but most must be replaced. When replacement is necessary, the exact type is preferred; however, universal type replacement is available. The
Figure 7-6. - Oven-heating circuit with two heating units.
manufacturer's instructions that come with a thermostat will give you the exact method for installing and calibrating the device.
Faulty wiring is the final check. Unless arcing damage is evident, test a wire by disconnecting both ends from the circuit; then check it with an ohmmeter. A good wire checks 0 ohms; a faulty one, infinity Table 7-2 is a guide that should help you when troubleshooting electric ranges; it lists the trouble, probable cause, and remedy.
A hot-water heater is nothing more than a metal water-storage tank with one or two electric heating elements, thermostatically controlled to heat water in the tank. Some of the electrical problems you may encounter are as follows: no power, defective thermostat, thermostat out of calibration, or a defective heater element or elements.
The hookup for a hot-water heater will vary depending on the size and application of each unit. Always refer to the manufacturer's manual for wiring instructions and the NEC for any special requirements. Most hot-water heaters that you will be installing will have a wiring diagram similar to the one shown in figure 7-7. The thermostat is in series with the
Figure 7-7. - Wiring connections for an electric water beater, having two heating unitsContinue Reading