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How to wire water heater for 120 Volts

Heating water more slowly during peak-price hours can reduce electric bill for some folks.
It still takes same amount of electricity to heat each gallon of water up to thermostat set point. And keep water at that temperature.
Typically, 240Volt heats 21 gallon per hour. 120Volt heats 5-6 gallons hot water per hour. Recovery is slower. And electric usage is spread across more time, so peak usage can be reduced.
How to wire water heater for 120 Volts
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Wires on top of tank can be connected to either wire color.
I prefer black-to-black and white-to-red, but it work either way.
Wire colors vary by brand of water heater, but basically all wiring follows same pattern.
How to wire thermostats
Thermostats are mechanical, and are not powered by electricity: How thermostats work

Change water heater from 240Volt to 120Volt

120Volt is slower recovery, and for homes with low consumption.
Or for homes with solar electric panels.
Or moving water heater to another location without 240Volt line

It still takes same number of Kwh to heat gallon of water.
General purpose of 120V is slower heating during peak electric pricing.
Not best strategy if consumer uses a lot of hot water, since all the hot leaving tank is replaced by cold entering tank, and new cold water must be heated to set point.

Typical 240Volt water heater will work when connected to 120V or 240V or any AC voltage. Do NOT connect DC voltage to water heater.

Hot wire from 120Volt breaker connects to Black wire at top of heater.
White Neutral wire connects to Red wire at top of heater.

Thermostats can be wired many different ways; Illustration shows typical household electric water heater. Wire color varies by brand, model and year of manufacture.
How to wire thermostats
How to change water heater temperature
How to wire off-peak water heater
See inside main breaker box
Changing from 240V to 120V will not work on American-Craftmaster-Whirlpool energy smart electric water heaters, or hybrid electric water heaters.
Review Energy Smart
Review GE heat pump/ hybrid water heater
circuit breakers are warm

Also use 120Volt strategy when main box is overtaxed

If main breaker is tripping. Main breaker stress test

If water heater breaker is getting hot and tripping.
Another strategy is to change elelments from 4500 watt to 3500 watt for slower heating and less draw off breaker
Water heater element 
Assumes 4500 watt element rated for 240V
Element wattage and voltage printed on end of each element
How to identify and replace elements
Wattage drops when voltage is reduced
See water heater label showing difference between 208V - 240V
Resistive loads such as light bulbs and elements will burn less hot when voltage is reduced. Examples: ordinary household dimmer for incandescent bulbs, or power brown-out when household voltage is reduced and light bulbs dim.
Same is true for water heater elements.
Lower wattage heats less water per hour See chart
Formula for 240-to-120V:

.25 or 25% x 4500 watts = 1125 watts
240 volt water heater circuit Move black wire to 120Volt breaker
Move white wire to neutral busbar:

Image shows typical 240V water heater circuit.

To convert to 120V: Move black wire from 240V breaker to 120Volt circuit breaker rated for correct amps.
30 amp breakers and 10gauge wire run cooler with less heat loss. Circuit is more efficient, and breaker box lasts longer.

Move white wire from 240V breaker to Neutral busbar where ground wire connects.
Some breaker boxes have separate Neutral busbar where white wires are connected.

Basic 240Volt water heater circuit
How to replace circuit breaker
How to install subpanel
30 amp DPDT switch
Hubbell 30 amp 120/277 WVB3.
For certainty, always Test switch terminals using continuity tester before wiring.
Practical wiring diagram
Hubble/ Bryant 3025 instruction sheet
Toggle water heater between 120Volt and 240Volt
Use 240Volt during times when electric prices are lower, and faster recovery is needed. Use 120Volt during peak prices when less hot water is used
Bring 120Volt from nearby outlet that has 12 gauge wire, or install lower watt elements if wire is only 14 gauge.

Using 30 amp Double Pole Double Throw switch
Also called: 30 amp DPDT switch
Bryant 3025 at Amazon

Connect 120Volt wires as Hot and Neutral. Black connects to 120Volt circuit breaker and White connects to neutral busbar.
Connect 240Volt wires as Hot1 and Hot2. Both wires connect to 240Volt breaker.
Select correct wire and breaker

30 amp maximum current/ safe limit 80% = 24 amps
Over-amped switch will feel warm/ hot
How to control water heater with ordinary switches
Double pole double throw 30 amp switch
Bryant 3025 at Amazon
At Global Industrial

Bring white neutral wire from breaker box, or nearby outlet
Leviton 3033 switch
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Use 30 amp 3-way switch to toggle water heater

Leviton 3033 switch at Amazon
Check spec sheet for amperage rating of switch
5500 Watt elements draw 23 Amps
4500 Watt elements draw 19 Amps
How to wire T106 timer

Toggle water heater between 240 Volt or 120 Volt using T106 timer

Move clock motor wire from Com to NO terminal
See more T1906 and T1975 timer wiring  15 minute on-off
Intermatic T106 and T105 timers
All Intermatic timers

Wires inside water heater do not change.
Elements and thermostats will work with 120Volt or 240Volt

Element watt consumption drops when voltage drops
No need to change breaker.
Just run additional neutral wire to timer.
Element rated for 4500 watts @ 240Volt, will consume 25% or 1125 watts @ 120Volt
Wire GE timer for 120-240 volts

Toggle water heater between 120Volt and 240Volt

Use SPDT timer with dry NO NC relay terminals to change water heater between 120Volt and 240Volt

Use 120Volt at peak-electric price.
Water heater recovers slowly with 120Volt.

Use 240Volt when electric prices are lower, and faster recovery is needed.

Intermatic GM40 series
Tork DTU40 timer
GE 15207 series timers
Dry terminals mean NO NC COM terminals are independent and receive no power when power is applied to timer clock on terminals H and N.
Change water heater temperature using timer
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Change water heater temperature using GM40 timer

Applies to Intermatic WHQ timer and  Tork DTU40 timer and GE 15207 series timers

240 Volt  

Intermatic GM series
Use timer for two different temperatures on electric water heater.

Either upper thermostat and element have power or lower themostat and element have power. But not both at same time.

Must install ECO-protected thermostat for lower thermostat.
Thermostat must sit flat against tank wall, and be covered with insulation.
Both upper and lower parts of tank are ECO-protected from overheating
Rewire tank so upper and lower parts are separate.
Use GM40 timer to switch power between lower and upper parts of tank.
Also use Intermatic WHQ timer, Tork DTU40, or GE15207 series etc.

Normal operation, the lower thermost and element receive power and keep tank at temperature set point. Upper thermostat and element have no power.
This is called 'redundant' water heater operation. This technique for heating tank more rapidly after cold water first enters tank.
How to wire thermostats

When timer activates, power to lower part of tank turns OFF. Power to upper part of tank begins. Upper thermostat is set for higher temperature.
Since tank is at regular temperature, the higher setting means upper element will turn ON and begin heating tank to higher set point.

Use this technique to heat water very hot for laundry cycle.
Disadvantage: The lower part of tank will cool rapidly as new cold water enters tank, so this technique is good for making short-term batches of hot water.

Also this wiring technique can be used for off-peak operation.
Install smaller wattage upper element, for example rated 240V/ 1500 watt.
During peak pricing, only the upper element is working, so amount of available hot water is reduced, and upper element heats more slowly, using fewer Kw per hour of operation.
During non-peak pricing, lower element is working, and tank resumes heating as expected.
Electric water heater recovery

Lower watt element heats more slowly

Peak price strategy: Reduce size of elements will cause less electric consumption per hour at peak price times.

Recovery Computation Formula
GPH= (watts x 3.412) / (8.25 x °Temp. Rise)
Timers that can be wired to toggle water heater between 120V and 240V
GM40 timer
Intermatic GM40 series
Intermatic GM40AVE
Et70215 timer
ET70000 series

GE 15207

GE 15132
Tork DTU water heater timer
Digital 240Volt
Tork DTU40
 Multimeters at Amazon
Continuity tester at Amazon
Multimeter: for testing voltage and continuity etc
Install electric meter on water heater
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How to install electric meter on water heater
Upper thermostats
See larger
Water heater thermostats at Amazon
How to replace thermostats

How to wire thermostats

Thermostats at Amazon
Take apart thermostats
Camco thermostat at Amazon
Thermostats can be taken apart to separate ECO from thermostat.
Or buy AO Smith part #9004716115 with NO NC terminals.

Read about 2 water heaters
Read about off-peak strategies

Additional links


Wire nuts and how to twist wire

Replace circuit breaker

How to twist wire

How to install gas water heater

How to install gas water heater

9 ways to save with water heater
How to test elements

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
Cutler Hammer C25BUB230A
Recirculation system
Hot water circulation system
Solar water heater
9+ ways to save with water heater

Motorized shut off valve

Anode rods

Clean sediment from tank
Low water pressure
Low water pressure

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Troubleshoot Bosch tankless

How to install tank-type gas water heater

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Sylvania Tork GE  Leviton Hagar Power pack

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Intermatic box timers:
How to set box timers
Troubleshoot box timers
Trippers and parts
Intermatic GM series
Intermatic parts
Intermatic trippers and parts
 Dayton Sprinkler timers Power pack
Wire T1906 and T1905 timers
Wire T-101 T103 T104 timers
Paragon timers and manuals
Tork TU universal timer
Westek box timers
Wire EH40 and WH40 timers
Tork timers and manuals
Tork TU universal timer
Troubleshoot intermatic
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Leaking water heater
Intermatic GM series
Intermatic GM series
Pool timers and manuals
Intermatic T104P201
Wire GE 15207 timer
Intermatic EH10 timer
EH10 timer

GE box timers
Gardena timers
Gardena T1030

Anode rods

Cost to run water heater

Replace circuit breaker

Clean sediment from tank

Low hot water pressure

Compare all water heater timers
Recirculation system
Hot water circulation system
Gas and electric water heaters Support the economy:
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Industrial and scientific Amazon
Intermatic control centers Control centers:
+ manuals and parts

All control centers and parts

Including Z-wave
box timers Compare box timers

Control with Z-wave
programmable timer Compare programmable timers

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

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Yard and Christmas timers Yard and Christmas timers
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