SERVICE. A.O. Smith RPVR-80E, *2**-120-E5 series, *P**-80-E5 series, R2VR-180E, R4MR-320E, *P**-55-E5 series, *4**-280-E5 series, RPVR-30K, *4**-280-X5 series, *4**-320-E5 series

SERVICE

WARNING!

Electric Shock Risk

Servicing should be performed on this water heater only after it has been disconnected from the power supply circuit(s). Failure to do so can result in severe injury or death from electrical shock:

• Disconnect power by opening the circuit breaker or removing the fuses before installing or servicing.

• Some models are connected to more than one branch circuit, and more than one disconnect switch may be required to de-energize the equipment.

• All branch circuits must be disconnected prior to service.

• Use a non-contact circuit tester to confirm that power is off before working on or near any electrical parts.

• Replace the water heater’s cover after servicing to reduce the risk of fire and electric shock.

Element Removal and

Replacement

WARNING!

• Working on an energized circuit can result in severe injury or death from electrical shock. Turn power off.

• Some models are connected to more than one branch circuit.

Disconnect all branch circuits before servicing unit.

• Check wires with a non-contact circuit tester to make sure power is o ff . When you are fi nished, be sure all covers are secured to reduce the risk of fi re and electric shock.

NOTICE:

A built-in alarm is also included. If water leaks inside your electric water heater, an alarm will sound to provide warning. Simply turn off power to the water heater at the circuit breakers, turn off the water supply, then correct the leak.

Figure 9: Non-Contact circuit tester

If you are not comfortable replacing a hea ng element yourself, have this work done by a quali fi ed person. To replace the hea ng element, you’ll need the following tools and supplies:

• Phillips head screwdriver

• Adjustable wrench (for point-ofuse models)

• Pipe wrench or slip joint pliers (for point-of-use models only)

• 1-1/2 inch element wrench or adjustable wrench (for element removal; two- and four-chamber models)

• Bucket

• Rag

• Hair dryer or compressed air

1

Check your water heater’s data plate for the correct wattage and voltage. Verify that your new heating element has the correct wattage rating and is sized correctly for your water heater.

Figure 10: Heating elements

2

Figure 11: Installed heating

element

Con fi rm that power is o ff by checking the wires with a non-contact circuit tester.

3

4

Open a nearby hot water faucet and run the water until it is cool.

WARNING! To reduce the risk of scalding, be sure the water runs cool before you proceed.

Close the inlet valve to the water heater , but leave the hot water faucet open to relieve pressure.

Con Ɵ nued...

22 • Electric Tankless Water Heater

5

Remove the heater’s front cover, then place a bucket under the water heater to catch any water that spills.

NOTICE: If you have a two- or four-chamber model, you must unplug the cover’s ribbon cable from the control board.

When you plug it back in later, it must be oriented correctly.

(See Figure 5, page 14.)

We recommend marking the connector and board with a marker. You will then be able to align the marks.

• If you have a point-of-use water heater, go to step 6.

• If you have a two- or four-chamber water heater, go to step 7 on page

24.

6

Point-of-use water heaters only:

6.1

Remove the heater’s top plate:

A.) Remove both screws which secure the top plate to the water heater.

(See Figure 12.)

B.) Lift and remove the top plate.

Figure 12.

Top View of Point-of-Use Model

Figure 13.

Point-of-use models:

Grommet Orienta on

Outlet Inlet

Grommets

6.3. Remove the old element:

A.) Slide the inlet and outlet grommets upward to provide clearance. (Figure 13).

B.) Remove the screws that secure the red and black wires to the top of the heating element. (Use the

Phillips screwdriver. Save both screws for later use.)

C.) Disconnect the green ground wire from the heating element. (See

Figure 14.) It is secured with a spade connector. Pull it straight up from the element to slide it off the terminal.

Figure 1 4.

Element in point-of-use heater

Top Plate Screws

Retaining Nut

Ground wire (spade connector)

D.) Unscrew and remove the retaining nut that secures the heating element (See Figure 14).

Use an adjustable wrench. You may also purchase an element replacement kit which includes a thin-walled socket. Call Technical

Support for ordering information.

NOTICE: During the next step, protect the circuit board from dripping water!

E.) Lift the element out of the water heater. NOTICE: As you lift the element out of the opening, wrap it with a rag to keep water from dripping onto the circuit board.

F.) Remove the brass ground ring from the top of the element. (See

Figure 15: Brass ring and flag terminal.) Set it aside for later use.

Figure 15: Brass ring and flag terminal

Flag terminal

Brass ground ring

(point-of-use models)

6.4 Install the new element:

NOTICE: Ensure that there is an O-ring installed above the threads of the element. (See Figure 20, page 25.)

A.) Insert the new element into its water heater opening.

B.) Place the brass ground ring on top of the element. Make sure that the flag terminal is positioned so that the ground wire can be reconnected easily (Figure 16.)

Con Ɵ nued...

Electric Tankless Water Heater • 23

C.) Secure the element by installing and tightening the retaining nut (Figure

14, page 23). earlier.

Do not overtighten.

D.) Secure the red and black wires onto the top of the heating element. Use the two screws that you removed

E.) Reconnect the green ground wire to the element’s ground terminal

(flag terminal).

6.5 Reassemble the point-of-use water heater:

A.) Reposition both grommets as shown in Figure 17. Ensure that their flat surfaces press firmly against the top plate when you reinstall it.

Figure 16.

Brass ring on point-of-use models.

B.) Reinstall the top plate and secure it with the two screws that you removed earlier. (See Figure 12, page 23.)

C.) Go to step 8 on page 25.

Figure 17.

Point-of-use models:

Grommet Orienta on

Outlet

Flat

Inlet

Grommets

Flat surface presses against inside surface of housing. See above.

Place brass ground ring on top of element.

<ĞĞƉŇĂŐƚĞƌŵŝŶĂů accessible.

7

Two- or four-chamber water heaters only:

7.1 Drain the two- or four-chamber water heater:

A.) Remove all six screws that secure the access plate beneath the element (at the bottom of the water heater). See Figure 18.

B.) Remove the access plate and allow the water to drain into the bucket.

C.) Clean the access plate and both seals.

D.) Make sure that both seals are seated properly, then reinstall the access plate. (Use all six screws that you removed earlier.)

Figure 18.

Access Plates:

Two- or Four-Chamber models only ͻ dǁŽͲĐŚĂŵďĞƌŵŽĚĞůƐ͗ one access plate ͻ &ŽƵƌͲĐŚĂŵďĞƌŵŽĚĞůƐ͗ two access plates

ĐĐĞƐƐWůĂƚĞ;ďŽƩŽŵŽĨŚĞĂƚĞƌͿ

7.2 Remove the old element:

A.) Remove the screws that secure the red and black wires to the top of the heating element (Figure 19).

Use the Phillips screwdriver. Save both screws for later use.

B.) Remove the heating element with an element wrench.

C.) Lift the element out of the water heater. NOTICE: As you lift the element and O-ring out of the opening, wrap them with a rag to keep water from dripping onto the circuit board.

Figure 19.

Top view of element

(two- or four-chamber model)

D.)

24 • Electric Tankless Water Heater

7.3 Install the new element:

A.) Insert the new element into its water heater opening. Make sure that the O-ring is positioned properly. (See Figure 20.)

Figure 20.

O-ring

B.) Tighten the element with an element wrench until it is snug, then tighten for 1/4 turn more.

C.) Secure the red and black wires onto the top of the heating element. Use the two screws that you removed earlier. Proceed to step 8.

8

Turn on the WATER supply to the heater.

9

Turn on a nearby hot water faucet to fill the heater with water.

Continue until all air has been expelled from the heater and pipes. If a

T&P valve is installed, operate it manually several times to allow any trapped air to escape.

10

Check for water leaks. Correct any leaks that are found.

NOTICE: Do not restore power until the circuit board and components are completely dry. If water has dripped anywhere inside the heater (during element replacement or leak check), dry it with a hair dryer or compressed air. Be sure to dry behind the circuit board.

11

If there are no water leaks, complete these steps:

A.) Two- or four-chamber water heaters only: Take the connector end of the cover’s ribbon cable and plug it into the control board.

(Plug it in where you see two rows of header pins close together, five pins in each row.) If necessary, refer to the “DISPLAY” callout in the wiring diagram for your model. (See “Wiring Diagrams” on page 29.)

NOTICE: The plug must be oriented correctly. (The correct orienta on is shown in Figure 5, page 14.)

If you plug it in backwards, it will not cause damage, but the display will not work. If the display does not work a er you have completed installa on, 1.) disconnect power at all branch circuits, 2.) disconnect the plug, 3.) rotate it 180-degrees, then 4.) plug it back in.

B.) Reinstall the water heater’s cover.

WARNING! Be sure the cover is reinstalled and secured to reduce the risk of fire and electric shock.

C.) Restore power to the water heater.

D.) Run hot water from a faucet to make sure that the water heater is working as expected.

Thermistor

(Temperature Sensor)

Replacement

WARNING!

• Working on an energized circuit can result in severe injury or death from electrical shock. Turn power off.

• Some models are connected to more than one branch circuit. Continued on page 27.

Disconnect all branch circuits before servicing unit.

• Check wires with a non-contact circuit tester to make sure power is o ff . When you are fi nished, be sure all covers are secured to reduce the risk of fi re and electric shock.

If you are not comfortable replacing a thermistor yourself, have this work done by a quali fi ed person. To replace a thermistor, you’ll need the following tools/supplies:

• Phillips head screwdriver

• 1/2-inch open end wrench

• Bucket (for draining the heater)

• Siphon transfer pump & towels

1

2

Turn o ff power to the water heater.

Drain the water heater as described in the draining instructions (page 27).

3

Locate the thermistor (temperature sensor) that was iden fi ed by the error code.

Refer to the appropriate fi gure on page 26.

Figure 21.

4

Unplug the thermistor’s wires from the control board.

Electric Tankless Water Heater • 25

Figure 22.

Thermistor loca ons

(Point-of-use models)

OUTLET INLET

Thermistor* Connections

T-Aux Auxiliary thermistor

T-In Inlet thermistor

T-Out Outlet thermistor

T-Aux **

T-In **

T-Out

Outlet Thermistor *

(Connects to T-Out)

Auxiliary Thermistor *

(Connects to T-Aux)

Inlet Thermistor *

(Connects to T-In)

* Often referred to as a temperature sensor.

** If the inlet thermistor fails, there is no need to replace it.

Simply switch the

T-Aux and T-In plugs on the control board.

POWER

SUPPLY

TERMINAL

BLOCK

NOTICE:

Appearance of cap may vary.

Figure 23.

Thermistor loca ons

(Two-chamber models)

OUTLET

HEATING ELEMENTS

INLET

Intermediate

Thermistor *

(connects to

TH-1)

TH-1

TH-2

TH-IN

L1

L2

Figure 24.

Thermistor loca ons (Four-chamber models)

OUTLET Intermediate

Thermistor *

(connects to

TH-2)

Intermediate

Thermistor *

(connects to

TH-1)

INLET

TH-1

TH-2

TH-3

TH-4

TH-IN

L1

L2

L1

L2

Outlet Thermistor *

May be located on outlet elbow.

(connects to TH-4)

Intermediate Thermistor *

(connects to TH-3)

Thermistor* Connections

TH-IN Inlet thermistor.

TH-1 Intermediate thermistor

TH-2 Intermediate thermistor

TH-3 Intermediate thermistor

TH-4 Outlet thermistor

* Often referred to as a temperature sensor.

Inlet Thermistor *

(connects to TH-IN)

Outlet Thermistor *

(connects to TH-2)

Inlet Thermistor *

(connects to TH-IN)

Thermistor* Connections

TH-IN Inlet thermistor.

TH-1 Intermediate thermistor

TH-2 Outlet thermistor

* Often referred to as a temperature sensor.

26 • Electric Tankless Water Heater

5

Remove the thermistor by turning it counter-clockwise with a 1/2-inch open end wrench.

6

Install the new thermistor in the opening by turning it clockwise with a 1/2-inch open end wrench.

□ Make sure that the O-ring is in place before you install the thermistor.

□ Tighten the thermistor hand tight, then carefully tighten it with a wrench until it is seated. Do not overtighten.

7

Plug the thermistor’s wires into the control board. The proper loca on is shown in one of the fi gures on page 26.

8

Return the water heater to service. To do so, follow the instructions in “Returning the

Water Heater to Service,” page 28.

Draining the Water

Heater

WARNING!

• Working on an energized circuit can result in severe injury or death from electrical shock. Turn power off.

• Some models are connected to more than one branch circuit.

Disconnect all branch circuits before servicing unit.

• Check wires with a non-contact circuit tester to make sure power is o ff . When you are fi nished, be sure all covers are secured to reduce the risk of fi re and electric shock.

Draining the Water Heater

1

Con fi rm that power is o ff by checking the wires with a non-contact circuit tester.

2

3

Open a nearby hot water faucet and run the water until it is cool.

WARNING! Be sure the water runs cool before draining the water heater to reduce the risk of scalding.

Close the inlet valve to the water heater , but leave the hot water faucet open to relieve pressure.

4

Remove the heater’s cover, then place a bucket under the water heater to catch any water that spills.

NOTICE: If you have a two- or fourchamber model, you must unplug the cover’s ribbon cable from the control board. When you plug it back in later, it must be oriented correctly. We recommend marking the connector and board with a marker. You will then be able to align the marks. See also

Figure 5, page 14.

• If you have a point-of-use water heater, go to step 5.

• If you have a two- or four-chamber water heater, go to step 6.

5

Point-of-use water heaters only:

Drain the point-of-use water heater:

A.) Remove both screws which secure the top plate to the water heater.

(See Figure 25.)

Figure 25.

Top View of Point-of-Use Model

Top Plate Screws

B.) Lift and remove the top plate.

(Removing it will protect if from damage.)

C.) Cover the top of the water heater with heavy towels (to prevent water from dripping through the openings).

A er the towels are in place, disconnect the inlet and outlet water lines from the water heater.

D.) Remove the hea ng element as described in “Element Removal and

Replacement” (page 22).

E.) Insert a pump hose into the water heater’s chamber and pump all of the water out.

F.) Reinstall the hea ng element as described in “Element Removal and

Electric Tankless Water Heater • 27

Replacement” (page 22).

G.) Reinstall the inlet and outlet water lines to the water heater.

H.) Go to step 7.

6

Two- or four-chamber water heaters only:

Drain the two- or four-chamber water heater:

A.) Remove all six screws that secure the access plate beneath the element (at the bottom of the water heater). See Figure 26.

B.) Remove the access plate and allow the water to drain into the bucket.

C.) Clean the access plate and both seals.

D.) Make sure that both seals are seated properly, then reinstall the access plate. (Use all six screws that you removed earlier.)

E.) Repeat steps A through D for each access plate.

F.) Go to step 7.

Figure 26.

Access Plates:

Two- or Four-Chamber models only ͻ dǁŽͲĐŚĂŵďĞƌŵŽĚĞůƐ͗ one access plate ͻ &ŽƵƌͲĐŚĂŵďĞƌŵŽĚĞůƐ͗ two access plates

ĐĐĞƐƐWůĂƚĞ;ďŽƩŽŵŽĨŚĞĂƚĞƌͿ

Returning the Water Heater to

Service

When you are ready to return

7

the water heater to service, turn on the WATER supply to the heater.

8

Turn on a nearby hot water faucet to fill the heater with water.

Continue until all air has been expelled from the heater and pipes. If a

T&P valve is installed, operate it manually several times to allow any trapped air to escape.

9

Check for water leaks. Correct any leaks that are found.

NOTICE: Do not restore power until the circuit board and components are completely dry. If water has dripped anywhere inside the heater, dry it with a hair dryer or compressed air. Be sure to dry behind the circuit board.

10

If there are no water leaks, complete these steps:

A.) Two- or four-chamber models only: Take the connector end of the cover’s ribbon cable and plug it into the control board. (Plug it in where you see two rows of header pins close together, five pins in each row.) If necessary, refer to the “DISPLAY” callout in the wiring diagram for your model. (See “Wiring Diagrams” on page 29).

NOTICE: If you have a two- or fourchamber model, you must orient the plug as shown in Figure 5, page

14. If you plug it in backwards, it will not cause damage, but the display will not work. If the display does not work a er you have completed installa on, 1.) disconnect power at all branch circuits, 2.) disconnect the plug, 3.) rotate it 180-degrees, then 4.) plug it back in.

B.) Reinstall the water heater’s cover.

WARNING! Be sure the cover is reinstalled and secured to reduce the risk of fire and electric shock.

C.) Restore power to the water heater. Verify proper operation.

Replacement Parts

The following parts may be ordered through your retailer or local plumbing wholesaler:

• Thermistors

(temperature sensors)

When ordering replacement parts, please be ready to provide your water heater model and serial number.

28 • Electric Tankless Water Heater