Search / all results
Search using Find button  

 Tweet button  
How to wire water heater for 120 Volts
How to wire 240 volt water heater for 120 volt generator
Basic wiring
How to wire water heater for 120 Volts
Larger image
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
Instructions: Move wires to single-pole breaker will change water heater from 240Volt to 120Volt
120Volt is slower recovery, and for homes with low consumption.

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 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.
Read how to convert AC water heater to DC/ high voltage
Convert AC water heater to DC/ low voltage
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 electronic water heaters such as American-Craftmaster-Whirlpool energy smart electric water heaters, or hybrid electric water heaters.
Review Energy Smart
Review GE heat pump/ hybrid water heater
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
Water heater will heat slower at 120 volt
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 21-47 gallon per hour. 120Volt heats 5-12 gallons hot water per hour. Recovery is slower. And electric usage is spread across more time, so peak usage can be reduced.
Water heater elementWattage 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

Assumes 4500 watt element rated for 240V
Element wattage and voltage printed on end of each element
How to identify and replace elements
Formula for 240-to-120V:
.25 or 25% x 4500 watts = 1125 watts
Voltage higher than element rating: result element burns out.
   Connect 240 volt 4500 watt element to 277 volt or 480 volt, and elements burn hotter and burn out
   Connect 120 volt 1500 watt element to 240 volt, and element burns 4x hotter 6000 watts and burns out
Voltage lower than element rating: result element heats less water per hour
   Connect 240 volt 4500 watt element to 208 volt or 120 volt, and elements burn cooler and heat less hot water per hour
   Connect 240 volt 4500 watt element to 120 volt, and element burns 1/4 power and heats at 1125 watts. Good for off-peak or generator.
How to replace element
Connect water heater to generator
circuit breakers are warm  Also use 120Volt strategy when main box is overtaxed
If main breaker is tripping. Main breaker stress test

generatorIf 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

Generator may not provide enough wattage for entire house: save generator capacity for other parts of house by toggling water heater to 120 volt using transfer switch
How to wire 240 volt water heater for 120 volt generator
30 amp DPDT switchToggle water heater between 120Volt and 240Volt
Max 4500 watt non-simultaneous water heater
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
Ordinary 3-way switch will do same job, but without center off
Also called: 30 amp 2 pole DPDT switch
Buy: double-pole double throw 30 amp
2 DPDT switch with center off 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
Figure volts amps watts for water heater
See inside main breaker box
Two water heaters
How to control motor with two switches
30 amp maximum current/ safe limit 80% = 24 amps
Over-amped switch will feel warm/ hot
How to control water heater with ordinary switches

For certainty, always Test switch terminals using continuity tester before wiring.
24 amp safe maximum
Practical wiring diagram
Wire diagram
Double pole double throw 30 amp switch
Buy double-pole double throw 30 amp
2 DPDT switch with center off at Amazon
2 DPDT switch with center off at Amazon
Larger image
Bring white neutral wire from breaker box, or nearby outlet
Leviton 3033 switch
Larger image
Use 30 amp 3-way switch to toggle water heater

Leviton 3033 switch at Amazon
Max amp rating for 30 amp switch is 24 amps
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
How to wire T106 timer
All Intermatic timers

T106 timer

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
30 amp safety cut off
30-Amp 120-240-volt Two-Pole Indoor Safety Switch with Neutral/ fusable
2-pole 30 amp non-fusable safety switch/ indoor / power cut-off
2 pole 60 amp non-fusable / outdoor box/ at Amazon

How to wire safety switch
You can use fusable or non-fusable
Having more than one fuse on same line is ok by code
Multimeter: for testing voltage and continuity etc
 Multimeters at Amazon
Continuity tester at Amazon
Timers 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
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.
Timers can be wired to toggle water heater between temperatures
Change water heater temperature using timer
Larger image
Change water heater temperature using GM40 timer
Applies toIntermatic WHQ timerTork DTU40 timerGE 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.
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

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
Solar water heater
9+ ways to save with water heater

Motorized shut off valve

Anode rods

Clean sediment from tank
Support the economy:
Buy water heaters from my associate links:

50 gallon Gas water heaters at Amazon
40 gallon gas water heaters at Amazon
50 gallon Electric water heaters at Amazon
40 gallon electric water heaters at Amazon
Hybrid / heat pump/ water heaters at Amazon

How to install gas water heater
How to install electric water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
Point of use water heaters
Troubleshoot Gas valves with manuals
Icon gas valve

How to replace water heater element Waste King disposal
How to wire tankless electric

Install point of use water heater
Titan tankless

Contactors/ relays
Install and troubleshoot garbage disposal Waste King disposal
Programmable timers

Woods timers
surge protection
Anode rods anode rods
Recirculation system

Tankless recirculation
Point of use water heater
Type 1 and type 2 surge protection surge protection
Industrial electric

Industrial supplies

Tools and home improvement

Home and garden

Hayward pool
Pentair pool

Southwire electric

Black and Decker

Irwin Hand tools
Klein hand tools
Fluke electrical testing
Dremel hobby tools

Campbell Hausfeld air powered
Tekton automotive

Powerbuilt automotive
Saws and saw blades
box timers Resource:
Compare box timers
DPDT timers
Control water heater w/ Z-wave
Intermatic control centers Resource:
Intermatic control centers: and parts
Digital control centers and parts
Tork control centers and parts
All control centers and parts
programmable timer Resource:
Programmable timers
Countdown timers
Off delay timers
On delay timers
Timer modules
Din rail
Twin & one-shot
Low voltage power packs Recirculation systems
Enter Amazon from my links

My response might end up in spam folder, check email folders
Waterheatertimer on Twitter