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How electric water heater works
How Electricity works with water heater elements:
The force of voltage pushes a flow of electrons (amperes) through the matrix (atomic structure) of the conductor (wire).
The wire always offers resistance to the flow of electrons. Resistance is like friction, and causes heat on the wire.
An undersized wire will cause more heat.
Typically, heat on an electric wire means energy loss. Too much heat on the wire, and the circuit breaker trips.

To avoid tripped breaker and energy loss, the 240 volt water heater is connected to a 30 amp circuit breaker with #10 gauge sheathed cable. All residential wiring must be rated 600 volt as seen printed on the wire or embossed on the cable sheathing.
Extension cords and other non-standard conductors are not permitted.

When the water heater is ON, the voltage pushes the amperage (electrons) through a coil of resistance wire located inside the element.
Resistance wire is tiny by comparison with #10 copper wire, yet engineered to get extremely hot without melting.
When the resistance wire gets hot, it causes the water to get hot.
Electric water heaters work with high efficiency because the #10 wires don't get hot, only the resistance wire and water get hot.
Ultra low watt density
Buy elements: 208-240 volt:
2500 watt 
3500 watt
4500 watt 
5500 watt
240 volt water heater circuit Wiring
Residential water is connected to 240 volt dedicated double breaker that serves no other load.
Use 30 amp breaker.

Resources:
Basic 240Volt water heater circuit
How to wire thermostats
Water heater is tripping circuit breaker
Figure volts, amps, watts
Wire and breaker size chart
How electric water heater works
Typical 240 volt household water heater has 2 heating elements .... the upper and lower elements.
Elements are controlled by upper and lower thermostats. Each element is connected to a thermostat.
Thermostats are mechanical bi-metal switches that read temperature through side of tank wall and turn elements ON and OFF. Typical water heater thermostats are not voltage specific, and are rated for residential 120 to 240 and any commercial voltages up to 480 volt, including 208, 277, 415, and 480 volt.

Residential water heater thermostats can be manually set to temperatures between 90ºF to 150ºF, or 110° to 160°F, depending on brand and calibration. High Limit trips at 170°F.
All thermostat settings are approximate ... all values  +/- 5%.
Higher temperature settings use more electricity.
Higher temps over 135°F risk scald and permanent injury.
Average bath shower 104°F.

Commercial water heater thermostats can have higher, more dangerous range of 120-180ºF. Maximum temperature allowed for water heaters of all types is 210°F before the TP valve releases water. Higher temps risk violent steam explosion if TP valve is capped off or removed.
Do not install high temperature commercial thermostats on residential water heater. It is unnecessary and dangerous.
Typical bath-shower is 104°F.

For safety and to avoid scalding, the recommended setting for all water heater thermostats (commercial and residential, gas or electric) that supply potable (drinkable) water into pipes where water can come in contact with people is 120°F.
Higher temperature commercial thermostats are used for dishwashing and other high-temperature applications that are often governed by health codes, or need for space heating etc ... but high temperatures are never introduced into water pipes where water can come into contact with people. A mixing valve is installed to temper or reduce temperature of very hot water to 120°F before it enters supply lines.
Resources
How to adjust thermostats
How to replace thermostat on electric water heater/ commercial and residential
How to wire thermostats
Advantages mixing valve
How to increase amount of hot water

Electric water heaters are non-simultaneous
Residential 240 volt 2-element electric water heaters are non-simultaneous, as can be seen on product label located on side of tank.
This means both elements are never ON at same time (simultaneously) unless specific wiring inside heater is changed significantly. One element is ON, or the other element is ON, or both elements are OFF.
How to wire water heater for simultaneous operation

Upper thermostat is main controller.
Starting with a cold tank, upper thermostat turns on upper element until top 2/3 of tank reaches temperature setting.
After top of tank is heated, upper thermostat turns-off upper element and sends power to lower thermostat which turns on lower element. Lower element runs until tank reaches temperature setting.
Lower element turns on-and-off during standby hours to keep tank temperature at thermostat set point.

There is no air inside tank
When hot tap is turned on at kitchen sink, hot water immediately exits top of tank.
Hot water travels through hot-side pipe until it reaches faucet.
At same moment hot leaves top of tank, new cold water immediately enters bottom of tank through plastic dip tube pipe.
To save energy, never turn on hot tap when using only cold... because new cold water that enters tank must be heated to set point.
Resources
Read about dip tube
9-ways to save with water heater

During 'standby' hours, between hot water use, lower element maintains tank temperature.
Lower element keeps water hot by turning-on approximately 1-4 minutes each hour throughout day and night which equals 45Kwh - 216Kwh each month for standby operation depending on tank efficiency, maintenance, and seasonal incoming cold water temperature. Newer tanks with more insulation, or tanks located in naturally warm area turn on less frequently.
Resources
See math charts for heating water    
Kwh hour calculations

Once hot water is used at faucet, cold water quickly fills bottom of tank. Lower element is a activated first, and when the upper part of tank is below set point, the lower element turns off and upper element turns on, and the heat cycle repeats.
The temperature of incoming cold water affects how much energy is consumed. In winter, the incoming water is colder. Colder water means the elements must heat longer to reach the thermostat set point. Average groundwater temperature  Tempering tank

Larger image
Typical operation sequence of residential non-simultaneous water heater

The energy smart water heater operates same as residential non-simultaneous 2-element tank described above.
The difference is energy smart uses electronic sensors, and proprietary electronic thermostat to measure temperature and activate elements.  Apcom part #318125-000
Order from Sears or manufacturer
Resources 
Whirlpool Energy smart electric
Convert energy smart to regular water heater
Types of water heaters

Commercial 3-phase electric water heaters
Commercial 3-phase electric is different than single-phase residential electricity.

3-phase balanced water heaters (pictured) have similarities to residential heaters, but can vary, often having 6-9 elements.

3-phase non-balanced commercial water heaters are very similar to residential heaters, and have just two elements, and can be converted to residential use with a few alterations in wiring.

Resources
What is 3-phase
3-phase water heater
Difference between single phase and 3-phase

Wiring
Illustration shows basic wiring for 2-element non-simultaneous residential water heater. Wire colors vary.
Resources:
How to wire thermostats
How to replace wire on water heater

Water heater voltage:
Electric water heaters work on any voltage 120, 208, 230, 240, 277 etc:
Resources:
How to connect water heater to generator
Convert water heater to 120Volt
3-phase water heater
Figure volts amps watts
Electrical Safety: manufacturers make a safe product
-WET water heater is dangerous.
Do not touch leaking water heater or water heater that is wet or was flooded without turning power off.
- Gas and electric water heaters are both connected to water pipes and can act as ground conduit for electricity.
Turn power OFF.
Always turn power OFF when working on electric water heater
Test for power without touching wire connectors
NEVER assume power is OFF

Buy:
Non-contact voltage tester Amazon
Electric testers at Amazon

Resources:
Water heater safety precautions
How to test electric power is off
Water heater element Elements
Volts and watts are printed on end of each element.
Check label on side of tank for for voltage and wattage <> tank wattage is element wattage
In 2-element tank, if lower element burns out, the amount of hot water is reduced.
On 2-element tank, if upper element burns out, the lower element stops receiving electric power so neither element works and no hot water is available.

Resources:
Figure Volts Amps Watts for water heater
How to identify and replace water heater elements
How change element and remove sediment
How to troubleshoot electric water heater
Convert water heater to 120Volt for slower heating
Elements
Elements screw in or bolt in depending on tank.
Water heater elements are resistive, and similar to electric stove burners, except designed to be immersed in water.
Elements instantly burn out if no water is inside tank.
Elements burn out for different reasons and can be replaced.
Resources:
How to test elements.
How to replace elements.

Resources:
How to troubleshoot electric water heater
Test upper thermostatThermostats:
Steel water heater tanks have anode rod that prevents tank from rusting.
Periodic inspection and replacement of anode rod will extend life of water heater
Save money by turning down thermostats For each 10ºF reduction, save 3-5%
Resources:
See how to turn down thermostat.  
How to increase amount of hot water
Resources:
How to adjust thermostats
How to replace thermostat on electric water heater
How to wire thermostats
Troubleshoot water heater
Basic water heater circuit
Add another thermostat to gas or electric heater

Tanks with two-elements are rated 240Volt
Larger image
Thermostats and elements must be covered with insulation
Cover, insulation and protector are necessary so thermostat can read correct temperature

Reset button on upper thermostat of electric water heater is a safety feature and will trip when water inside tank reaches dangerous 170°F
Remove upper cover and insulation to access reset button. Firmly push in reset button. If reset will not engage, then let tank cool before trying again. If problem persists, replace thermostat.

Resource
How to troubleshoot electric water heater
Water heater insulation
Larger image
Install:
Electric heater can be installed inside any unventilated space, for example a closet with door closed
Electric water heaters do not burn hydrocarbon fuel and require no incoming oxygen supply or vent to outside.

Water heater is steel tank, covered with insulation, and surrounded by metal shell
1) Steel tank holds pressure of hot water.
2) Tank can be rusted and leaking.
3) Insulation helps prevent heat loss. Install in naturally warm area helps efficiency.
4) Metal tank shell protects wires from damage.
5) Any short to metal tank will trip breaker. Ground wire must be connected to water heater.
6) Do not expose water heater to rain or water.
Resources:
Read about flooded water heater.  
Read about leaking water heater
Anode rod
How to install electric water heater


Anode rod:
Steel water heater tanks have anode rod that prevents tank from rusting.
Periodic inspection and replacement of anode rod will extend life of water heater

Resources:
Anode rods
 
Dip tube: Cold water enters tank through dip tube

Resources:
Read about dip tube
Remove short water heater nipple
New water heater making noise

For safety, manufacturers make a safe product
Each tank  has TP valve that releases water when temperature exceeds 170-180ºF.
Temperatures above 180ºF can damage tank.

Resources:
How to test and replace TP valve
TP valve code

Drain valve:
Plastic drain valve and brass drain valves have 3/4" thread, and fit garden hose

Resources:
How to replace drain valve
Water heater will not drain
Leaking water heater


Tanks used for solar collectors must be rated for high temperature.
Resources:
Questions to ask before buying glycol solar system
Convert AC water heater to DC water heater
Convert AC water heater to DC water heater low voltage
Batch solar water heater


Advantages of electric over gas:
Electric heaters cost more to operate than gas heaters.
But electric heaters can be maintained to last forever, are cheaper to buy and install, can be installed in small confined areas, can be connected to solar power, can have additional insulation, can be installed in dusty dirty environment like basement, workroom, shop, laundry, are not affected by exposure to household chemicals, do not puff out hydrocarbon byproduct at each home, are easy to fix and alter using generic off the shelf parts

Resources:
Which is best gas water heater
Troubleshoot electric water heater.
Solar PV water heater.
How to wire thermostats.
Compare timers.
Is gas clean burning
How to maintain water heater
Anode rods
Two water heaters
Energy guide
The yellow label shows estimated yearly cost for average family of 4. Yearly cost estimates can help when comparing water heaters, but actual cost varies widely.
The label also shows 'first hour delivery' of heater. First hour delivery is amount of hot water a fully heated water heater can deliver in the first hour period. It doesn't mean the hot water will last an hour. Calculate first hour

Water heater standards changed April 2015. New heaters are about 2% more efficient, except new standard is based on 125° testing temperature instead of older standard 135°. The lower temperature means less hot water in tank, which means lower first hour delivery.
Every pound of hot water that leaves the tank is replaced by cold water that is heated and kept heated until next time hot is used.
Increase amount of hot water
Cost of running electric water heater at various rates
9-ways to save with water heater

EF or energy factor is NOT efficiency.
EF is a formula for calculating efficiency. There is a subtraction factor: EF = 0.960 – (0.0003 x V). V is volume, or tank gallonage. 40 gallon heater: .96 - (.0003 x 40) = .95 efficiency. As it turns out, the subtraction factor is so small that 30 gallon, 40 gallon and 50 gallon electric heaters each have .95 efficiency.
See chart with new and old EF factors
Water heating math
9-ways to save with water heater
How to wire off-peak water heater.

Electric heaters cost more to operate than gas heaters. However, electric heaters can be maintained to last indefinitely, are cheaper to buy and install, can be installed in small confined area, can be connected to solar power, wired several different ways, easily controlled with timer and home automation.
How to control water heater with timer and home automation
How to maintain water heater
cleaning tank to maintain efficiency

Manufactures have added more foam insulation to new water heaters. Most tanks come with heat-trap nipples or heat-trap inserts. Some heat traps can clog or cause whistling. Read about pressure issues and replacing manufacturer's heat-traps
 How to replace wire on water heater
Gas water heater
Unlike electric water heaters, Gas water heaters need supply of air to support combustion
Gas water heater

How gas water heater works: atmospheric and power vent

Gas water heater parts
Larger image

Resources:
FVIR flammable vapor system
Troubleshoot gas water heater
How to adjust temperature on water heater
How much does it cost to run gas water heater
Which is best gas water heater
Gas water heater parts
Larger image
Gas water heater parts
Read about FVIR flammable vapor system

Troubleshoot gas water heater

How to adjust temperature on water heater

Multimeter
Test for breaks in wire/ Test for voltage
Most appliance require 80% rated voltage to function correctly
Buy
Analog multimeter
Multimeters at Amazon
Klein multimeter
Electric testers at Amazon
Clampmeter for testing amp flow on line
Resource:
How to test and replace element
How to test thermocouple
Element tests for 120 volts
How to test wire
Safety when testing wires:
Never touch wet or previously flooded appliance.
Never stand on wet surface when working on electric.
Never stand on bare soil, put down dry boards.
Tape tester leads to wood sticks to keep hands away from power.
Use non-contact voltage tester before touching wires.
Never touch or lean into any made of metal.
Remove metal objects from pockets.
Do not use oxygen or fuel accelerants in same room as electrical repairs

Resource:
Basic house wiring

Non-contact voltage tester
Test for power without touching connectors
NEVER assume power is OFF

Buy:
Non-contact voltage tester Amazon
Electric testers at Amazon
Resource:
How to test electric power is off
GFCI receptacle120 volt 15 amp devices including GFCI, timers, switches, plugs, wifi controls etc can be installed on 15 or 20 amp breaker.

120 volt GFCI, outlet, receptacle that is rated 20 amp can be installed on 20 amp breaker only, but NOT on 15 amp breaker.  
Buy
15 amp GFCI
20 amp GFCI
Buy
Basic electric book
Home plumbing/ electrical codes
Basic electric book
Or learn about basic household electricity... use and search my site/
Resource
Safe electric wiring
Basic house wiring

Use outlet tester to check for correct wiring on any 120 volt straight-blade outlet.
Buy:
Klein testers
Outlet tester
Circuit breaker finder
Electric usage monitor
armored cable
Non metallic flexible cables must carry ground wire, but do not have hazard of short circuit causing injury from shock.

Armored steel cable can be used as a grounded connection, and will protect wires from damage. Metal can be energized from an insulation failure.

All conduit ...metal, plastic ... flexible and rigid ... must be attached to structure, and attached to enclosures, boxes.
Movement, damage and deterioration are major cause of electrical failure.
Buy:
Non-metallic flexible conduit
Power whip
Armored cable
Southwire armored cable cutter
Pull boxes
Southwire armored cable cutter
Electrical tools must be insulated.
Always best to disconnect power, but insulation failure, lack of proper grounding, grounded neutral, lack of GFCI, out-of-code wiring, generator operating without transfer switch, and other problems still pose a risk to anyone working on electric power ... even when breaker is off.

Buy:
Electrician tools kits
KLEIN TOOLS
Tools kits
IRWIN tools
KNIPEX
Connect wire to screw terminal
Use only 600 volt solid copper wire.
Do not use stranded wire or extension cord.
Do not use solder anywhere on residential 120-240 volt wiring.
Attach electric installation to structure. Tighten screws very tight against wire.

Buy:
NEC books
Dewalt plumbing/ electrical codes
Basic electric book
National electric code guide/ illustrated

Resources:
How to twist wire
How to select and install twist-on wire connectors
Lever switchWeatherproof lever switch on outdoor lights
Safely operate outdoor toggle switch
Replaces outdoor cover
Install over top of ordinary switch
Works with single-pole, double-pole, 3PST, 3-way, 4-way switches etc
Use weatherproof box for outdoor
Can be used indoor or outdoor

Buy:
Best choice: Cantex lever switch
Outdoor lever switches at Amazon
Lever switches

Resource
Cantex-toggle-switch-covers.pdf
Cantex-PVC-junction-boxes.pdf

Treminals

Terminals

Buy:
Terminal kit
Blue for 16-14 wire
Yellow for 12-10 wire

Resource:
How to install terminal
Push on wire connectors

Push-on wire connectors in place of twist-on connectors

Buy:
Push on wire connectors Amazon
Red 3P connector for 10-14 gauge wire
Lever connectors for stranded wire at Amazon

Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage cable or wires inside cable.

Code
-Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15
Buy
End cutting nippers at Amazon

 


When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistances on wire and creates weak point.
Buy tools:
Wire strippers at Amazon
Linesman pliers
Pro linesman plier
Needle nose pliers
End cutting nippers at Amazon

Weather resistant plastic box for outdoor extension cord connections, Christmas lights, outdoor power strip etc . Not for connecting wires with wire nuts®, or in-wall wiring, but can be used indoors to organize extension cords, power strips etc.
Weather resistant is not weatherproof or watertight. Use enclosures rated IP65 and IP67 for waterproof.
Extension cords cannot be used for permanent wiring.
Buy:
Large-medium-small electric cord box
Socketbox
Raintight enclosures
Water-tight cord lock
Resource: Enclosures and boxes
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

Resources:
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
Resources:
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
Type 1 and type 2 surge protection surge protection
Programmable timers

Woods timers
surge protection
Anode rods anode rods
Recirculation system

Tankless recirculation
Point of use water heater
Install and troubleshoot garbage disposal Waste King disposal
Buy
Electronic parts

Industrial supplies

Tools and home improvement

Home and garden

Hayward pool
Pentair pool

Southwire electric
Buy
Tools

DEWALT
Black and Decker
Stanley
SKIL
Makita
Porter-Cable
Bosch

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
Intermatic
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
Subpanels
All control centers and parts
Enclosures
programmable timer Resource:
Programmable timers
Countdown timers
Off delay timers
On delay timers
Timer modules
Din rail
Twin & one-shot
Woods
Intermatic
Tork
Low voltage power packs Recirculation systems
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