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Electric Water Heaters

elements (Figure 16-1), with each element controlled by a thermostat. The thermostats

are mounted on the outer wall of the water heater tank just above the elements, from

where they sense the temperature of the water through the outer wall of the water heater

tank. A temperature and pressure-relief valve, which is mounted on the outside of the tank,

is a device applied to a water heater, which will open to pass water or steam if excessive

pressure or temperature occurs in the water heater tank.

Electric water heaters are available in many different heights, widths, and capacities.

Principles of Operation

The water heater tank is full of water, the electricity is on, and the upper thermostat (see

Figure 16-1) senses that the water is cold. This condition energizes the upper element. At the

same time, the lower element is not activated. The upper heating element will heat

approximately one-quarter of the tank’s capacity. When the temperature of the water reaches

the thermostat setting, the upper thermostat will shut off. Then the lower thermostat becomes

energized and heats the remainder of the water in the tank. When the temperature of the

water reaches the thermostat setting, the lower thermostat will deactivate the lower heating

element. The tank is now filled with hot water. As the consumer uses the hot water, it is drawn

from the top of the tank and is replaced with cold water through a dip tube (see Figure 16-1)

located near the bottom of the tank. When the lower thermostat senses the cold water, the

thermostat activates the lower heating element, heating the water. Figure 16-2 identifies one of

the many types of thermostats. The figure also shows a schematic drawing of the thermostat

switch contacts.

Safety First

to maintain or repair any electric water heaters. Any improper installation, preventive

maintenance, or repairs could create a risk of personal injury or property damage.

If you do not fully understand the preventive maintenance or repair procedures in this

chapter, or if you doubt your ability to complete the task on your electric water heater,

please call your service manager.

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CHAPTER

These precautions should also be followed:

it is full of water.

FIGURE 16-1

Exploded view of the

electric water heater.

PART VI

thermostats.

plumbing, and placement of the tank be done by qualified personnel. Observe all

local codes and ordinances for electrical, plumbing, and installation procedures.

Before continuing, take a moment to refresh your memory concerning the safety

procedures in Chapter 2.

Electric Water Heaters in General

Much of the troubleshooting information in this chapter covers electric water heaters in

general, rather than specific models, in order to present a broad overview of service

techniques. The pictures and illustrations that are used in this chapter are for demonstration

purposes only, to clarify the description of how to service these heaters. In no way do they

reflect on a particular brand’s reliability.

Reset

Two top

terminals

High

limit

Upper

4 thermostat

2

1

3

Adjust

Adjust

Lower

thermostat

Upper

element

heating

High

limit

1 4

3 2

Upper

thermostat

Upper

heating

element

Lower

heating

element

Lower

thermostat

Lower

heating

element

(a)

(b)

208/240 V

Electric Water Heater Maintenance

Every so often, inspect the water heater tank for possible water leaks. Check the following:

there is serious water damage to the property.

and insulation for signs of water leakage. If water is leaking, the leak must be

repaired or the unit must be replaced immediately.

Once a year, the water heater tank should be drained and flushed out. This will increase

the life expectancy of the tank by removing any unwanted sediment. Before you begin

draining the tank, turn off the electricity to the water heater. Then turn off the water supply

to the tank. Connect a garden hose to the draincock, and open the valve. To increase the

water flow draining out of the tank, open the hot water faucet. When you are ready to refill

the tank, close the draincock and turn on the water supply to the water heater.

Leave the closest hot water faucet open during refilling; the air that is trapped in the

tank will escape through the hot water faucet. When all of the air is out of the tank and

water lines, turn off the hot water faucet. Go to all of the other hot water faucets and open

them to remove air in the lines. Turn off all water faucets. Now you are ready to turn on the

electricity to the water heater.

Step-by-Step Troubleshooting by Symptom Diagnosis

In the course of servicing an appliance, don’t tend to overlook the simple things that may be

causing the problem. Step-by-step troubleshooting by symptom diagnosis is based upon

diagnosing malfunctions, with their possible causes arranged into categories relating to the

operation of the water heater. This section is intended only to serve as a checklist to aid you

in diagnosing a problem. Look at the symptom that best describes the problem you are

experiencing with the water heater, and then proceed to correct the problem.

No Hot Water

1. Do you have the correct voltage at the water heater?

2. Check for loose wiring.

3. Make sure that the reset button did not trip.

4. With the electricity off, check the thermostats for continuity.

5. With the electricity off, check the heating elements for continuity. Also check for

a grounded heating element.

Not Enough Hot Water

1. Is the water heater undersized for the usage?

2. Check the lower heating element for continuity. Also check for a grounded heating

element.

3. Check for leaking faucets and pipes.

PART VI

4. Check to see if anyone is wasting water.

5. Drain the tank and remove the lower element. See if any sediment is in the bottom

of the tank or around the heating element.

6. Is there any lime formation on the elements?

7. Are the thermostats operating properly? Run a cycle test.

8. Check the thermostat settings. Verify if they are set too low.

Water Too Hot

1. Check to see if the thermostat is snug against the tank.

2. Is the thermostat set too high?

3. Are the thermostats operating properly? Run the cycle test.

4. Check for a grounded element.

Water Heater Element Failure

1. Check for loose or burned wiring connections.

2. Check for the correct voltage to the elements.

3. Is the element shorted or grounded? Test the elements for continuity.

Discolored or Rusty Water

1. Drain the tank and remove the lower element. See if there is any sediment in the

bottom of the tank.

2. Is the water supply to the water heater rusty in color?

3. Check the water for softness.

4. Check to see if there are excessive mineral deposits.

5. Inspect the anode rod to note its condition. If it has dissipated, replace the anode.

Repair Procedures

Each repair procedure is a complete inspection and repair process for a single water heater

component, containing the information you need to test a component that may be faulty

and to replace it, if necessary.

any electric dryer. Any improper installation, preventative maintenance, or repairs will

create a risk of personal injury, as well as property damage. Call the service manager if

installation, preventative maintenance, or the repair procedure is not fully understood.

Upper Thermostat

The thermostat is a mechanical device that controls the flow of current to various parts of

the water heater. The thermostat senses the heat from the tank wall. When the thermostat

senses the heat, it can control the current that is sent to the upper element or to another part

of the water heater tank. The upper thermostat is attached to the high-limit thermostat.

The typical complaints associated with the upper thermostat are:

To handle this problem, perform the following steps:

get hot?

the water heater. Is the water heater installed properly? Does the water heater have

the correct voltage?

electricity. This can be done by pulling the plug out of the electrical outlet. Or

disconnect the electricity at the fuse panel or at the circuit breaker panel. Many

installations have a disconnect switch/breaker box near the water heater. Turn off

the electricity. The voltage at the receptacle is between 198 volts and 264 volts

during a load on the circuit (see Chapter 6).

be removed (see Figure 16-1). The access panel is held on with two screws on most

models. Peel back the insulation and then remove the thermostat’s protective cover.

on the 300-volt scale. Touch the probes to terminals 1 and 3 above the reset button

(Figure 16-3). Turn on the electricity. If the meter reads no voltage, have the customer

call an electrician to find out where the power failure is. If the meter reads the proper

rated voltage, as stated on the name plate, the electricity is okay. Next, touch the

probes to terminals 2 and 4 below the reset button (Figure 16-4). If the meter reads

the proper rated voltage, the electricity is okay. If the meter reading is “0” volts, press

the reset button on the thermostat. If there is still no voltage reading on the meter scale,

either the water temperature in the tank is too hot or the thermostat is inoperative. At

this stage, turn off the electricity to the tank again. Remove the wires from the upper

heating element (Figure 16-5). Be absolutely sure that the electricity is off before any

further tests are made using your ohmmeter.

Use your ohmmeter to test terminals 1 and 2 on the upper thermostat (see Figure 16-5).

If the thermostat is calling for heat, the ohmmeter needle will swing to the right,

showing continuity. Now touch the probes to terminals 1 and 4 on the thermostat

(Figure 16-6). If the water in the tank is cold, you will not get a reading on the

ohmmeter scale. If the water in the tank is hot, as called for by the thermostat, the

needle will swing to the right, thus showing continuity.

electricity to the tank. Take your ammeter and clamp the jaws around the wire that

goes from terminal 4 to the upper element (Figure 16-7). With cold water in the tank

and the thermostat calling for heat, you should get a reading on the meter in amps.

PART VI

1

2

3

4

110

120

140 130

150

160

170

THERMOSTAT

2 4

1

2

3

4

110

120

150 140 130

160

170

T H E R M O S T A T

2 4

probes on terminals 1 and 3 to

check the voltage.

probes on terminals 2 and 4 to

check the voltage.

element. Place the ohmmeter probes on

terminals 1 and 2. When the thermostat

is calling for the element to come on, the

ohmmeter scale will read continuity.

1

2

3

4

110

120

150 140 130

160

170

T H E R M O S T A T

2 4

probes on terminals 1 and 4. If

water in the tank is cold, the

ohmmeter scale will read no

continuity.

1

2

3

4

110

120

150 140 130

160

170

T H E R M O S T A T

2 4

The reading you get will depend on the rating (in watts)

of the heating element, divided by the voltage supplied

(see the formula in Figure 16-8). After the temperature is

reached, the needle on the ammeter scale will read “0.”

Next, place the ammeter jaws on the terminal 4 wire

that goes from the upper thermostat (just below the

temperature gauge setting) to the lower element

(Figure 16-9). The ammeter should show a reading,

indicating that the lower element is working.

to the water heater. To replace the upper thermostat,

remove all of the wires from the thermostat. Be sure

that you mark the wires so that you can replace them

exactly the way you took them off. Next, pry back the

thermostat retaining bracket with your fingers far

enough to slide the thermostat up and out; remove the

thermostat.

1

2

3

4

110

120

150 140 130

160

170

T H E R M O S T A T

2 4

the terminal 4 wire go to the element.

W

V2

A

V

Conversion chart for determining amperes, ohms, volts, or watts

W

V V

W

V

A

W

A2

W

A V2

􀀁

chart for determining amperes, ohms, volts, or watts.

around terminal 4. The ammeter reading

is 0.

1

2

3

4

110

120

150 140 130

160

170

THE RMOS T A T

2 4

PART VI

turn on the electricity to the water heater. Repeat this testing process as described,

and verify that the new unit is working correctly.

Lower Thermostat

The lower thermostat monitors the water temperature in the lower section of the water

heater tank. The lower thermostat turns on and off the lower element.

Testing the lower thermostat is similar to testing the upper thermostat, with the following

exception. With the wires removed from the element, place the ohmmeter’s probes on each

terminal. Take a screwdriver, place it on the set screw of the thermostat, and turn it clockwise.

The needle on your ohmmeter will swing to the right, indicating that there is continuity. If the

needle does not move, the thermostat needs to be replaced. Replace this thermostat as per the

upper thermostat replacement procedure previously described. Then test the thermostat by

placing the jaws of the ammeter around the wire that connects to the lower thermostat. Check

to be sure that the thermostat cycles on and off.

Heating Element

The heating element is made from a nichrome filament, surrounded by magnesium oxide

powder for heat transfer, and is encased in an immersion-type casing. This type of heating

element cannot be turned on unless there is water present in the water heater tank to

submerge the heating element.

The typical complaints associated with the heating element are:

To handle this problem, perform the following steps:

get hot?

the water heater. Is the water heater installed properly? Does the water heater have

the correct voltage?

electricity. This can be done by pulling the plug out of the electrical outlet. Or

disconnect the electricity at the fuse panel, the circuit breaker panel, or the disconnect

switch. Turn off the electricity. The voltage at the receptacle is between 198 volts and

264 volts during a load on the circuit (see Chapter 6).

panel must be removed (see Figure 16-1). The access panel is held on with two

screws on most models. Peel back the insulation and then remove the wires from

the heating element.

the ohmmeter scale will show continuity. If the element is bad, the ohmmeter needle

one probe and place it on either terminal of the element. Take the other probe and

touch the element head (Figure 16-11) or the tank. If you get any reading, the element

is grounded and should be replaced. Repeat this procedure for the other terminal on

the element. Both terminals must be measured for grounding.

water supply. Connect a garden hose to the draincock, and open the draincock. At the

same time, open a nearby faucet to allow the water to drain faster. After the tank is

empty, disconnect the wires from the element and remove it. The screw-in type can be

removed by using a 1½-inch socket or a 3/8-inch socket for the four bolt–type elements.

procedure, and reassemble. When installing the new element, always replace the

gasket. Before you insert the new element into the tank, clean the flange of debris.

the draincock, and open the water supply. Close the nearby faucet after all of the air in

the tank has dissipated. Next, check for water leaks. Turn on the electricity to the water

heater. Use the ammeter to check the element. The ammeter should show a reading.