Search / all results
Search using Find button  

 Tweet button  
Connect electric water heater to generator
Connect any 2-wire voltage to ordinary household water heater, and it will heat water.
120V 277V 208V 230V 240V 250V  3-phase non-balanced etc
Do not rewire inside water heater
Connect either voltage wire to either wire on water heater
Do not exceed 30 amps, 4500 watts
Figure volts amps watts for water heater
Single phase generator feeding 3 phase panel


Do NOT touch wet water heater or water heater that was flooded
Flooded water heater
Connect generator to water heater Ordinary electric water heater can run on any voltage from any direction (excluding volt/amp ratings below amount needed to heat tank of water, for example typical 12 volt battery will not heat tank of water).

Voltages include single-phase, split phase, and 3-phase residential/commercial voltages with either 50 or 60 Hz.
3-phase water heater
How to wire thermostats

Install line fuse if wattage exceeds 4500 Watts.
30 amp fuse would be required to prevent wires from overheating, and eliminate fire hazard.

This information does NOT apply to energy-smart electric water heater with box on top of heater, or newer energy smart with electronics, or to hybrid water heaters, or heat pump water heaters with delicate electronic circuitry.

Why it works like this:
Ordinary electric water heater thermostats are mechanical bi-metal switches and respond to tank temperature, and are not operated by electricity.
Ordinary generic electric water heater thermostats switch electricity on-off using mechanical bi-metal switch.
Heat elements are simple coil of thermal wire that gets hot when voltage is applied.
The element will get hot when power is applied.


Turn off main breaker
If main breaker is ON, the generator will energize power company wires... this will delay power company repairs and make it dangerous to be around downed power wires
Remember power company wire are bare metal.... they can appear totally harmless until you touch or step on the line... then you can get killed or badly burned
Flooded water heater


When working with electricity: Stand on dry boards, never assume power is off, keep hands away from electric wires, use insulated tools, do not stand in water, do not use oxygen.
Attach electric water heater to generator Use 12 gauge wire, or 12 gauge extension cord.
Any voltage will work

With smaller gauge extension cord, do not run for long distance.
240 volt water heater works with any AC voltage/ 120 or 240 etc.
Voltage must be less than rating printed on end of each element.
For example 240 volt element will work fine with 120 volts...
... but 120 volt element connected to 240 volt will burn out element

240Volt 4500 watt heats 21-42 gallons per hour
240Volt  3500 watt heats 16-33 gallons per hour
Smaller voltage, smaller watt output = fewer gallons per hour.

Most generators want loads balanced across all outlets.
balanced means each outlet draws same amount of wattage.
Unbalanced loads can affect power generation, and life of product..

If you connect generator to whole house power, then turn main breaker OFF

Assumes 4500 watt element rated for 240V
Element wattage and voltage printed on end of each element
How to identify and replace element
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
Formula for 240-to-120V:

.25 x 4500 watts = 1125 watts

Question: Is it OK to use Low Wattage water heater elements for heating water using a generator?
For example, I live in Florida and have a 5500 watt generator.
During hurricane season I would like to replace the two 4500 watt elements in my water heater with two 1500 watt elements.
Answer yes.
But ....

Might be easier to connect water heater to 120 volt and leave elements in place
240 volt 4500 watt element heats 21 gallons per hour
Connect 120 volt and elements run cooler... they run at 1/4 wattage or 1125 watt... same 4500 240 volt element, connected to 120 Volt... will produce 1125 watts and heat 5.25 gallons per hour

Elements are resistive load... just like a light bulb
When there is a brown out, or less voltage, then light bulbs dims. Less light when voltage drops. Less heating on element when voltage drops.

My understanding is that it is important to balance loads on generator when using 120 volt on a 240 volt generator. Read generator manual.
So if 120 volt outlet is pulling 1125 watts, then other loads on generator should equal same 1125 watt

Important: If your generator only produces 240 volt, or you do not want to mess with balanced loads... then install 1500 watt elements.

Important: buy elements rated 240 volt 1500 watt.... and that will heat about 7 gallons per hour.
Voltage and wattage is printed on end of each element.
Following link shows a few 1500 watt 240 volt elements.

MOST 1500 watt elements are rated 120 volt... to fit into small under-sink tank
Caution:... If element rated for 1500 watt 120Volt is plugged into 240 volt, the element would run at 4x the wattage or 6000 watts... and in theory it should burn out quickly.
Same if you connect ordinary 120 volt 100 watt light bulb to 240 volts... it will burn very bright for a few moments before burning out.

4500 watt element heating 21 gallons per hour is based on 60 degree rise in temperature...
For example incoming water temperature is 60 degrees F, and thermostat is set to 120 degrees... requiring 60 degree rise in temperature.
... except incoming water temperature in Florida is about 67-77 degrees F... so if your thermostat is set to 120 degrees, your water heater would heat more than 21 gallons per hour.
generator 120 and 240 volt generators are used for homes and construction businesses etc
Check the total wattage output, portability vs need
If you are connecting the power to you household electric panel, you MUST turn off main breaker and disconnect from power company service ... or use a transfer switch.

Generators at Amazon

Generator manual
How to wire twist-lock plug for generators
How to wire transfer switch
30 Amp Generator Transfer Switch Kit 30 Amp Generator Transfer Switch Kit/ 7500 watt
When generator comes on, then transfer switch automatically disconnects power from main breaker.
If generator is connected directly to breaker box during power outage, then power can exit wires leaving house and energize power lines outside.
The live wires can slow repair work by power company.
Can also create danger power on neighbor's wires, which they may think have no power.
So bulbs at neighbors house glow very dimly as if there is still power available.
Always turn off main breaker when connecting generator to breaker box
30 amp transfer switch at Amazon
50 amp automatic transfer switch at Amazon

Reliance 31406CRK manual/pdf
Generator interlock

Generator interlock
Reliance transfer switch TCA series: Reliance transfer switch/ manual operation
Purpose of transfer switch: Keep generator isolated from the utility at all times.
100 amp
Up to 15000 watt generator
Unit is ON when utility power is ON
Unit has two breakers that are interlocked... neither breaker can be ON at same time

Reliance transfer switch/ 100 amp indoor/ at Amazon
Reliance transfer switch/ 60 amp indoor/ at Amazon

Reliance TC series transfer switch manual:
Why ground wire is needed
120-240 volt generator 120-240 volt generator
120-240 volt generator has 3 coils. A center coil that rotates. Two outer coils that sit 180 across from each other.
The center coil is electromagnet with North and South poles that rotates 60 times per second.
Each time the center coil passes Coil 1, it creates a pulse of electricity on Line 1.
Electricity is the flow of electrons across the surface of a conductor. Wire is one type of conductor.
Each time the North pole of center magnet passes Coil 1, the flow of electrons on Line 1 goes one direction. Then when the South pole of magnet passes Coil 1, the flow of electrons on Line 1 reverses and goes the other direction. This is called AC or alternating current. Up and down the electrons continually move on Line 1.
The voltage on Line 1 rises and falls as the magnet passes and the electrons slow down, stop and then reverse direction. When the electrons come to a stop the voltage is zero. And then the electrons reverse direction and voltage goes up.
At two points in each cycle, the voltage drops down to zero, and then the voltage goes up again. Up and down the voltage rises and falls.. However the average voltage is above 0, and the generator rotates so quickly that the up-and-down voltage is not seen... and Line 1 tests120 volt to ground at all times. Line 2 also tests 120 volt to ground at all times. Testing Line 1 to Line 2 shows 240 volt potential.
Grounding for the generator is supplied by connection to the ground busbar located in main breaker box, or by installing a ground rod and making a ground connection from water heater. Grounds and Neutrals are separate, but must be bonded (connected) together.

Coil 1 and Coil 2 are out of phase with each other, so Coil 1 and Coil 2 produce a reverse flow of electrons from each other. When electrons on Line 1 are flowing away from Coil 1 toward the house, at the same time, electrons on Line 2 are flowing toward Coil 2 and toward the generator.

Generator must have a balanced Load. What that means is that Line 1 and Line 2 must supply the amount of wattage as each other. So if you have 100 watt bulb connected to Line 1, then you need 100 watt bulb connected to Line 2.
You cannot run 1000 watts on Line 1 and 0 watts on Line 2, or the generator will overheat.
Calculate the wattage of each circuit by looking at appliance labels, and using the basic formula Volts x Amps = Watts.
Balanced loads apply only to the 120 volt circuits. When connecting 240 volt, the load is aromatically balanced, because the same wattage is pulled from each Line.
If 120/240V generator is rated for 5000 watts, then Line 1 carries 2500 watts and Line 2 carries 2500 watts.
Generator outlet Generator outlet box wiring:
4-prong generator outlet wiring: All 4 prongs are locking.
all 4 prongs are rounded
1 prong is rounded with upturn.... this it the ground connection
Prong located opposite the ground connection is Neutral connection
If there is no neutral wire, then do not connect any wire to neutral connection
Other two prongs are for hot wires
3-prong generator outlet wiring: All 4 prongs are locking.
all 3 prongs are rounded
1 prong is rounded with upturn.... this it the ground connection
Other two prongs are for hot wires
There is no neutral connection

Twist lock plug / 30 amp/ at Amazon
Twist lock outlet / 30 amp/ at Amazon
4-prong 30 amp generator outlet
Generator outlet boxes at Amazon
4-prong 30 amp generator outlet/ 7500 watt at Amazon
3-prong 50 amp generator outlet / 12,500 watt at Amazon
Cook and stay warm with charcoal briquettes if you have no power
Heat well house or pump house with briquettes
Use metal pan, galvanized bucket.
Set bricks in circle on concrete step stone.

Do NOT use gasoline.
Never use gasoline as accelerants.

Use charcoal lighter fluid.
Use newspaper, cardboard, old book to get fire started.
Use WD40.... as last resort... but ONLY small amount on dry briquettes before fire is added... can of WD40 will explode in face.

Smoke will aggravate asthma
CO2 will be put into air and can cause death if no ventilation
Be damn careful now.
Electricity leaves power plant Resource: Electricity:
The grid is defined by three parts: transmission, distribution and end user. The following links show how it works
Power plant to end user power pole
Power pole to residential breaker box
Power pole to commercial breaker box

How to wire residential electric
How to wire commercial 3-phase

Why you need ground wire
How to wire 3-phase timer
3-phase water heater
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

How to install tankless recirculation

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
Electronic parts

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