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How to select and replace thermostat on electric water heater

How to replace thermostat on gas water heater
Upper and lower thermostats
thermostat temperature range

Buy residential upper and lower thermostats

Thermostats are interchangeable/ each works with your water heater
Temperature range 90-150F is standard for residential water heaters
High limit is the temperature that causes reset button to trip is 170F
Buy 90-150 degree F for residential tank:
Water heater thermostats at Amazon
Camco thermostats at Amazon
More thermostats
89T short/ dual-element thermostat at Amazon
Example Camco dual-element thermostat at Amazon

Commercial water heater thermostats

Buy commercial upper and lower thermostats

Buy/ 3 phase water heater thermostat 120-180 degree F
Camco 120F to 180F thermostat (commercial grade only)
Camco 180F lower thermostat (commercial grade only)
Read more about 3-phase water heater

Residential tank thermostat is rated 90-150 F
Residential TP valve will release water at 150 degrees F
Only use 180 F thermostat on commercial water heater that is rated for high temperature

Marathon water heater is rated 170 degrees F

Break apart therm-o-disc dual element thermostat and you get: 66T DPST manual reset bi-metal switch/ high limit 170F  + 59T SPDT regulating thermostat with 60 degree adjustabe range
DIY help for 2 water heaters: Make lower thermostat from upper
Read about two water heaters

Best to replace both thermostats.
There is no guaranteed way to test themostats.
If thermostat is sticking, then test includes rotating temperature knob which can temporarily unstick thermostat. So bad thermostat appears to work correctly.

Add another thermostat to gas or electric water heater
All bi-metal thermostat temperatures are approximate
Typically, bi-metal thermostats have triggering range from 5 to 15 degrees for SPST and 17-27 degrees for SPDT.
So tank temperature can drop considerably before thermostats activate, and manufacturer can say 'it's normal'.
Wide range can be annoying if you continually run low of hot water, simply install new thermstat for better results. 
Close range can cause TP to release water after several short draws of water from tank... because top of tank is already hot but added cold water activates thermostat and lower element heats more hot that makes top of tank overheat.
Thermostats can stick occasionally and come out of calibration or simply stop working
Upper Thermostats
    Single element     Dual element          Larger image
dual element thermostat
Larger image

Difference between single-element / dual-element thermostat

Thermostat for dual-element tank has 3 screws on right side.
Thermostat for single-element tank has 2 screws on right side.
Dual element thermostat will work in place of single-element, but single-element thermostat will not work for dual.

All dual-element and single-element thermostats works on 120V / 208-240V/ 277V / 480V etc
All thermostats are generic and can be used in place of each other... except you cannot use single for dual
Upper thermostats have ECO reset button that trips when temperature reaches 150-170
Buy from my links:
Single element thermostat/ therm-o-disc
Single-element thermostat/ 89T style at Amazon
Single element thermostat/ Aprom style
You can use dual element thermostat/ not necessary to buy single element
Water heater thermostats at Amazon

Therm-o-disc sell sheet/ pdf
89T thermostat kit
89T thermostat

89T thermostat kit

Buy from my affiliate links
Shorter style 89T single-element thermostat at Amazon
89T13 dual-element thermostat at Amazon
89T13 dual element kit with jumper wire

Shorter style 89T single-element thermostat at Amazon
89T short/ dual-element thermostat at Amazon
Therm-o-disc thermostat protectors

Thermostat protectors/ for therm-o-disc upper and lower thermostats

Terminal protectors for therm-o-disc// Does not fit Apcom style
Protectors are important when inspecting water heater and pushing reset button without risk of electrocution
Never stand on wet surface or outdoor soil... always put down dry boards to stand on
Do not touch or lean into anything made of metal when working on water heater that has power.
Never touch wet water heater or water heater that was flooded... make certain power is OFF

Upper element terminal protector
Lower element terminal protector
All brands of thermostats are interchangeable

for 2 low density 240 Volt 4500 watt elements/  + Upper and lower thermostat

Buy LOW density kit:
Apcom plumbers pack Amazon

How to replace elements

$35 for 2 high density 240 volt 4500 watt elements + Upper and lower thermostat

Apcom thermostats
Buy HIGH density kit:
Apcom plumbers pack Amazon

How to replace elements

New water heaters have high density elements. Low density elements might last longer
$45 for 2 low density 240 Volt 4500 watt elements/+ Upper and lower thermostat

Therm-o-disc thermostats
Buy LOW density kit:
Therm-O-disc low density plumbers pack

How to replace elements
$45 for 2 high density 240 Volt 4500 watt elements/ + Upper and lower thermostat

Therm-o-disc thermostats
Buy HIGH density kit:
Therm-O-disc high density plumbers pack
Therm-O-disc high density

How to replace elements
gas water heater themostat Resources for gas:
Identify and troubleshoot gas water heater thermostat
How to replace gas water heater thermostats

Replacement steps start here

220 Volt circuit breaker
Power if OFF
Do not empty water out of heater

Turn power OFF

Turn off 20 or 30 Amp circuit breaker to 240V water heater See basic water heater wiring diagram
Or 20 Amp circuit breaker to 120V water heater

Check label on side of water heater for appliance voltage Figure volts amps watts
Wattage is stamped on end of element see example

water heater element

Never assume power is OFF/ Use non-contact voltage tester

Use non-contact voltage tester on timer, on wire, on outlet to see if power is present.
Press button on tester, if single beep then no power is present. If continuous beep then power is present.
Never stand on bare ground, always stand on dry boards, do not hold or touch anything metal when working on timer or water heater that has power, tape tester leads to wood sticks, never touch wet water heater, or flooded water heater, or timer that had a short or fire without turning power OFF.

Multimeters at Amazon
Buy non-contact voltage tester at Amazon
Electric testers at Amazon

Shop Amazon - Industrial and scientific
Shop Amazon - Industrial Electric Products

Test water heater
How to find age of water heater

How to use ordinary tester/ 120, 208, or 240V:

Stand on dry boards
Never touch wet water heater unless power is OFF
Tape tester leads to wood sticks

1. Test black wire to ground wire

2. Test black wire to white wire

3. Test white wire to ground wire

If indicator lights up, then electricity is present.
water heater thermostats
Newer tanks have foam insulation that may need to be cut back. Insulation must be re-installed.

Do not empty water out of heater

Not necessary to wait for water to cool. Can be done with hot water inside tank.
Power must be OFF.
Use screwdriver to remove covers and insulation from tank

Some 240Volt tanks have single access door and single thermostat
Buy new parts that match old
Buy parts at hardware store
Thermostats and elements are generally interchangable between brands of electric water heater
Exception is Whirlpool energy-smart shown lower on page.

Thermostat cover
Thermostats usually covered with plastic protector shield.
New protector shield packaged with some new thermostats
Purpose of protector is to protect homeowner from electrocution when pushing reset button or adjusting temperature when power is ON.
Older heaters may not have plastic shield.
Upper element terminal protector
Lower element terminal protector
water heater thermostat

Take photo of wires ... before starting

Take photo of wires or draw picture showing location of each wire
Replace water heater thermostat
Larger image
See large image of overall wiring diagram
Wire colors can vary
Take photo of wiring before starting.

See upper thermostats showing numbers

Steps to replace thermostat

Instructions are same for both upper and lower thermostats
Power is OFF, and tested that power is off using steps above

Use digital camera and take photo of wires or draw picture showing location of each wire
Remove wires from thermostat
Thermostat is held in place by metal spring that snaps over ears on thermostat
Pull back metal spring on both sides (make a tool using piece of coat hanger wire)
Slide out old thermostat
Put new thermostat in place, wiggle thermostat around to make sure it is held flat and tight against tank by metal spring
Thermostat reads temperature through surface of metal tank
Use screwdriver to adjust temperature
See images showing how to adjust temperature to 120 (or higher if hot water runs short)
Re-connect wires <> tighten screws very firm against copper wire
Important .... Push-in red reset button firmly to make sure it is engaged
After thermostat is replaced, put factory insulation back over thermostat
Insulation must cover thermostat to avoid higher water temperatures than desired set point
Tank must be full of water or elements will instantly burn out
Turn power ON
Put ear against water heater to hear bubbly fizzing sound that says water heater is 'on'
If tank is fully heated, water heater will not turn on. If tank is partially heated, then lower element will turn on. If tank is cold, then upper element will turn on. How it works
Put access doors back on tank
Access doors and insulation are required for thermostat to read correct temperature

If water heater is still not working, see troubleshooting
Burned thermostat
Burned thermostat

What caused it?
Electricity found path from terminals on thermostat to bare metal tank. But fire did not spread because tank factory-installed covers and insulation were on side of tank
Always connect ground wire to water heater
Always keep insulation and cover installed on tank.

Inspection finds Burned thermostat or melted wire

Turn power OFF
Replace part
Test wires

Multimeters at Amazon

How to test water heater wires

Test wires with Multimeter
Multimeters at Amazon

Fire safety

Fire safety

All wires must be same gauge (same diameter). Or connect different gauge wires using push-on wire connectors
Only copper wire used.
Solid wire only. Never use stranded wire.
Only copper under screw plate, no insulation under screw plate.
Maximum 2 wires under screw plate.
Wires must be fully inserted under screw plate. And screw plate very tight against wires.
Wires cannot run over top of thermostat or elements, and must be pushed aside.
Wires can run over top of other wires, but not at point where wires are making connection to either element or thermostat.

Use push-on wire connectors when wires are too short

Push on wire connectors at Amazon
Red 3P connector (shown) for 10-14 gauge wire
Yellow 4P for 12-18 gauge wire
Push on wire connectors
Back of thermostat

Thermostat must sit flat against tank

Wiggle thermostat to make sure it sits flat against tank
Thermostat sits flat against tank wall so temperature reading is accurate and water heater is protected from overheating

Access doors and insulation must be put back over thermostat to avoid higher water temperatures than desired set point, which leads to overheating, which will trip ECO reset.

See larger

Double-check thermostat wiring

Compare wiring with illustration

How to wire thermostats
How water heater thermostats work

Red reset button:
ECO energy cut off turns off power to water heater when temperature reaches 150-170
Test upper thermostat

Adjust temperature on thermostat using screwdriver.

Recommended temperature is 120 degrees F for efficiency and to avoid scalding water.
If home is running short of hot water, turn temperature up.
Thermostat setttings are approximate. Calibration is different for each thermostat. Use cooking thermometer to measure water temperature when exact temperature is needed.

Problems from high temperature setting include higher bill, faster sediment build-up.
Minerals can distill out of water when water is above 140 degrees.
Water expands with higher heat. TP valve releases water. Pressure should not exceed 80 psi.
How to adjust water heater temperature
9 ways to save with water heater
Test and replace TP valve.
Install expansion tank.
Inspect for leaks once per year.
Test for high water pressure over 80psi that can damage tank and pipes
Formulas and terminology

Insulation and cover must be over thermostat.

Exposing thermostat to cool room temperature will cause tank to overheat.
Thermostat cannot read correct temperature unless covered correctly.

Upper element terminal protector
Lower element terminal protector

Troubleshoot electric water heater
Water heater leak

Inspection finds leak/ rust around element

Replace element and gasket
Inpect anode rod
Leaking water heater resources
How to install electric water heater
circuit breaker

Circuit breakers/ push fully OFF / and then fully ON

Water heater is tripping breaker
How to replace circuit breaker
How to wire gfci
Can AC breaker be used for DC breaker
How to reset circuit breaker
Not enough space for circuit breakers
Circuit breakers
How to install subpanel
Why you need ground wire
Match breaker and wire size
How to wire subpanel
See inside breaker box
How to wire safety switch
How to wire whole house surge protector
Figure volts amps and watts
Figure correct wire and breaker
electric thermostat on gas water heater

Add another thermostat to water heater

For example turn off power to recirculation pump that pumps water from solar panel or secondary tank...or control electric water heater from the gas water heater... or turn off solenoid valve that turns off gas line... or connect to indicator light to notify when tank reaches set point... or connect to solenoid water valve that turns on hot water. Thermostat is mechanical and will work with 12-12 Volt AC-DC, 120-208-240, 277 volt AC electricity.

Add another thermostat to gas or elctric water heater
magnetic thermostat switch
Bi-metal thermostat with magnet for all kinds of DIY projects

Bi-metal thermostats/ fireplace, furnace, cooling fan etc

Magnetic .... no bracket needed.
ON at 120F / OFF at 90 F... use relay if you want OFF at 120F and ON at 90F
Rated 15 amps @ 120 Volt. Works with any voltage 12-24-28-120-208-240-277
Mechanical switch requires no voltage to operate switch
Buy 90-120 degree F thermostat:
Magnetic thermostat kit at Amazon
Thermostat switches at Amazon
Adjustable thermostat 90-120
Oven thermostat
Bi-metal thermostat switch limits
T36 therm-o-disc

Additional information

Water heater construction

Steel tank is covered by insulation and metal shell.
Insulation and shell protect wiring.
9 ways to save with water heater

Anode rod is necessary to stop steel tank from rusting
Basic parts on top of electric heater
Parts vary slightly depending on model and brand

Anode rods
Test and replace TP valve
Water heater valves
Replace drain valve
Water heater will not drain
Dip tubes
Low water pressure
Flooded water heater must be replaced:

Insulation is wet.
Wet water heater is immediate electrocution danger. Turn power OFF.
Insulation cannot dry unless covers are left off tank.
Covers are required for thermostat to read correct temperature.
Water heater must be taken out of service until completely dry.
Flooded water heater
Leaking water heater
Non simultaneous operation 240 volt residential water heater is wired for non-simultaneous operation:
Both elements are not ON at same time.
Upper is ON, or lower is ON, or both are OFF.
Action is controlled by upper thermostat.

How thermostats work
How electric water heater works
Water heater must be full of water or elements instantly burn out.
How to fill water heater:
Turn tub spout ON until full stream.
Open water heater TP valve for a moment to release last of air.
Turn power ON.
How to test elements
How to replace elements
How electric water heater works
How to test and replace TP valve

Additional links

Electricity from pole to breaker box

See basic 120V and 240V water heater circuits

Compare all water heater timers
Do it yourself
Do it yourself water heater

How to twist wire

How to wire off-peak water heater

How to install and troubleshoot gas water heater
Leaking water heater
Troubleshoot leaking water heater
Cutler Hammer C25BUB230A
Recirculation system
Hot water circulation system
Troubleshoot Rheem tankless

Troubleshoot Bosch tankless
Solar water heater
9+ ways to save with water heater

Motorized shut off valve

Anode rods

Clean sediment from tank
Gas and electric water heaters Industrial electric at Amazon

Industrial supplies at Amazon

Industrial and scientific Amazon
Shop Amazon - DEWALT
Shop Amazon - Black and Decker
Shop Amazon - Stanley Tools
Shop Amazon - SKIL Tools
Shop Amazon - Porter-Cable Tools
Shop Amazon - Bosch Tools
Shop Amazon saws and saw blades
box timers Compare box timers

Control water heater w/ Z-wave
Intermatic control centers Control centers:
+ manuals and parts

All control centers and parts

Including Z-wave
programmable timer Compare programmable timers

Control water heater with programmable wall timer
Countdown timers Compare countdown timers

Control water heater with countdown timer
Low voltage power packs Low voltage transformers

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