Repairs for Water Heaters | How to fix electric water heater

Breakdowns of both gas and electric water heaters are caused most often by the malfunction of an easily replaced electrical part. On electric water heaters, it is the high powered heating elements or the thermostats that burn out; on gas heaters, the faulty part is usually the electrical safety device that keeps the gas flowing. Available at home improvement centers and water heater dealers, all of these inexpensive parts are simply fitted onto or into the tank wall after the water heater is turned off and, in some cases, drained.

Leaks, however, are far more serious. A water leak in the tank itself calls for replacement of the water heater; leaks in the gas line require the immediate attention of a professional.

The cause for the breakdown of an electric water heater is pinpointed with a multitester, which isolates a broken electrical connection in a thermostat or a heating element. The elements, particularly the lower element (most electric water heaters have two), are more likely to fail than any other part, and both should be replaced even if only one has failed. The new elements should have the same wattage, voltage and attachment fittings as the old.

The upper thermostat of an electric water heater is harder to test than the lower one, because the arrangement of terminals varies with the model and the thermostat can be hooked up in as many as five different ways. The simplest way to determine whether the upper thermostat has failed is by a process of elimination: Test all the rest of the circuits first. Since upper thermostats differ, a faulty one must be replaced with one of the same type, identified by a number on the dial. All lower thermostats and high- temperature cutoffs (opposite), however, are interchangeable so long as they are made for the same voltage, since they work in the same way.

Unlike electric water heaters, gas models use electricity only in the thermocouple, a safety device that shuts off the gas when the pilot light goes out. The thermocouple is a short rod that converts heat from the pilot flame into a minute amount of electricity, which in turn holds open the valve that admits gas to the burner. Eventually a thermocouple may become too weak to hold the valve open, so the heater shuts off. Suspect the thermocouple first when this happens, and replace it.

To operate at peak efficiency, both gas and electric water heaters need preventive maintenance. Test the temperature- pressure valve (opposite) at the top of the tank every year by pushing down the valve handle and letting out some water. If the valve fails to release water, it is clogged and should be replaced. Unscrew it from the tank top after shutting off the heat and draining the tank. If the valve leaks after you release the handle, operate it several times to wash out accumulated sediment. Also, once a year open the drain cock and let out about 5 gallons of water to prevent sediment from accumulating on the bottom of the tank.

An Electric Water Heater

How an electric water heater works

The two heating elements of most electric water heaters are controlled by a pair of thermostats wired so that only one element can heat atatime. In normal usage, hot water leaving the tank from the top is replaced by cold water entering the tank through the bottom of the dip tube, and the lower thermostat, sensing the drop in temperature, turns on the lower element. If a great deal of hot water is being used, the upper thermostat turns on the upper element and shuts off power to the lower thermostat and element; thus the water at the top ofthetank is heated first.

To protect the tank from corrosion, a magnesium rod-called the sacrificial anode-is slowly consumed by galvanic corrosion, which would otherwise destroy the tank's walls. To keep the tank from overheating, the temperature- pressure valve at the top of the tank vents the water if it reaches a temperature of 210° F, and a high-temperature cutoff preset at 190° turns off the power to the entire heater.

Finding an electrical failure

First check the main service panel for a blown fuse or tripped circuit breaker Then turn off the power to the water heater and remove the cover from the heater controls. Clip the leads of a multitester, set at 250 volts, to the two top terminals of the high- temperature cutoff, and turn on the power at the service panel. If the meter reading is not twice the voltage tested at a standard wall outlet, then the fault is in the house wiring.

If the meter reading is correct, the water heater is at fault; turn off the power to the water heater and let the tank water cool to lukewarm, Then, with the power off, disconnect the heating elements, set the multitester at RX1, and test the following pairs of terminals for continuity: the two left and two right terminals on the high-temperature cutoff (if there are cutoffs for both thermostats, test both); the upper and lower heating-element terminals; and the lower thermostat terminals. On each test, the meter's needle should indicate continuity. If it does not, the circuitry in the heating elements or the lower thermostat is defective, but the circuitry in the cutoff may be good. Press the cutoff's reset button and test the cutoff again. If the needle still does not indicate continuity, the cutoff circuitry is faulty too.

To test a heating element for a short circuit, touch one meter probe to the tank wall or the mounting bracket of the element, the other probe to either terminal of the element. If there is continuity, the element is short-circuited.

If your water gets too hot even with the thermostats set low, and the heating elements are good, test the lower thermostat s response to high temperatures by holding it over a lighted candle. Within 30 seconds you should hear a click; test the terminals immediately. If there is continuity, the lower thermostat Is broken.

If both of the heating elements-as well as the high-temperature cutoff and the lower thermostat-pass these tests, it is safe to assume that the upper thermostat is broken.

Replacing heating elements

Turn off power to the water heater and remove the panels covering the controls. Connect one end of a garden hose to the tank’s drain cock, and run the other end to a floor level house drain. Turn off the cold-water supply valve and open the drain cock, as well as all the hot-water faucets in the house. When the tank has been completely drained, disconnect the heating element wires from their terminals, and unfasten the elements from the tank. Some elements, like the one shown here, bolt directly onto the tank; others (inset) screw into it.

Screw or bolt the new heating elements to the tank, using the new gaskets provided. Close the hot-water faucets and the drain cock; then turn on the cold-water supply to refill the tank. To check whether the tank is full, open a hot- water faucet anywhere in the house above the top of the tank and wait for water to gush out; the elements will burn out immediately unless they are covered by water. Reconnect the element wires and replace the cover panels. Then restore power to the water heater.

A Valve to Shut Off the Gas

Replacing a thermocouple. With the gas turned off at the water heater's gas control, unclip the large brazed end of the thermocouple (inset) from the pilot bracket underneath the water tank. Then use a wrench to unscrew the small end of the thermocouple from the magnet fitting on the gas control on the side of the tank.

To install the new thermocouple, reverse the procedure. First screw the small end of the thermocouple to the magnet fitting until it is finger- tight; then give it a quarter turn more with a wrench. Bend the copper connecting wire into a gentle curve, then clip the large brazed end into the pilot bracket so that the pilot flame will cover V2 inch of the tip, Turn on the gas and light the pilot according to the manufacturer's instructions printed on the tank.