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How to wire water heater for 120 Volts
How to wire 240 volt water heater for 120 volt generator
Use only 600 volt wire.
Lamp cord, extension cords are not rated 600 volt.
Use copper wire only. Aluminum wire is fire risk and should be avoided or installed by professional.

30 amp breaker use 10 gauge /
120-240 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire ... cannot be connected to 15-20-40 amp breaker.

Orange/ #10 gauge wire, with ground ... 30 amp capacity. Safe maximum: 30 x 80% = 24 amps.
Buy:
10-2 gauge/ 30 amp
10-3/ 30 amp
Southwire electric tools
Yellow 12 gauge 20 amp
120 volt 20 amp outlet can be installed on 20 amp breaker, but not 15 amp breaker/ use 12 ga wire.
... cannot be connected to 30-40 amp breaker. 1

Yellow/ #12 gauge wire, with ground ... 20 amp capacity. Safe maximum 16 amps.
Buy:
12-2 gauge/ 20 amp
12-3/ 20 amp

NMB is house wiring
UF is underground
Rolls of stranded wire
HOOK UP Wires
White 14 gauge 15 amp
120 volt 15 amp outlet, AFCI, GFCI, timer, switch etc can be installed on 15 or 20 amp breaker. Never connect 15 gauge wire to 20-30-40 amp breaker.

White/ #14 gauge wire,  with ground ... 15 amp capacity. Safe maximum 12 amps.
Buy:
14-2 gauge/ 15 amp
14-3/ 15 amp

NMB is house wiring
UF is underground
50-60 amp breaker use 6 gauge /
240 volt 50 outlet can be installed on 50 amp breaker only
6-2 wire
Buy:
6-2 wire
Southwire electric tools
NMB is house wiring
UF is underground
40-50 amp breaker use 8 gauge /
240 volt 40 amp outlet can be installed on 40 or 50 amp breaker only
6-2 wire
Buy:
8-2 wire
Southwire electric tools
NMB is house wiring
UF is underground
     
Copper ground wire.
Every device, load, metal enclosure etc must be grounded. Ground wire must be continuous throughout installation, never switched on-off, never used as a Neutral wire.
Generally ... use same size as other wire in circuit
Buy:
12 gauge copper ground wire
Ground wire
Green ground wire
Ground pigtails
Ground rods/ ground clamps at Amazon
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

Telephone cable knife
Low Voltage Mounting Bracket for Telephone
stranded wire
600 volt 12 ga Stranded wire ot THHN wire is good for conduit with multiple wires ... but stranded cannot be installed under screw terminals on outlets, switches, timers etc without risk ... of heat causing splayed strands ....that come loose ... and begin to arc. Connect stranded to short piece of solid copper wire, and attach solid to screw terminal. Do not solder residential or commercial wiring.

Project wire, extension cords, thermostat, bell and automotive wire are not rated for residential or commercial wiring. Only wire maked 600 volt can be used for permanent household wiring.
Buy:
Southwire 600 volt stranded wire
Rolls of stranded wire
HOOK UP Wires

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

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


Electrically insulated tools
When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistance and heat on wire and creates possible weak point.
Buy tools:
KLEIN TOOLS
Wire strippers at Amazon
Electric Wire Stripping Machine
Linesman pliers
Utility knife at Amazon
multimeter
Multimeters
Voltage is tested across two separate wires. Ohms or resistance is tested across both ends of same wire. Amperage is tested along one or two points on same wire.
Buy:
Analog multimeter
Multimeters at Amazon
Klein multimeter
Electric testers at Amazon
Clampmeter for testing amp flow on line

GFCI circuit breaker
A GFCI circuit breaker will protect all boxes on circuit.

Circuit must be grounded. Ground wire must be continuous and connected to each piece of equipment.

White wire on circuit breaker must be connected to Neutral busbar inside the breaker panel.

Buy
GFCI circuit breakers
Push down
single-pole breaker
1" wide Push down breaker
Plug-in breaker
Buy single-pole:
Choose from 15 to 60 amp
Eaton CL series
Siemens 15-60 amp

Single-pole tandem breaker
Tandem breakers
Push down
double-pole breaker
2" wide Push down breaker
Plug-in breakers
Buy double-pole:
Choose from 15 to 125 amp
Choose from 15 amp to 200 amp
Eaton CL series circuit breaker
Siemens circuit breaker
Double pole GFCI
Are you wiring a 120 volt water heater?
Does it have 2 elements (dual elements)? Or one element (single element)?
Upper Thermostats
Single-element thermostat         Dual-element thermostat 
2 screws on right side           3 screws on right side  
See Larger           
You CAN use dual-element thermostat for single-element tank
You CANNOT use single for dual tank
  
Single element thermostat/ 120V or 208V or 240V 
Same thermostat works for all voltages
Screw numbers are 1 thru 4
Single-element is identical to dual-element thermostat, except all dual-element upper thermostats have 3 screws located on right side.
You can use dual-element thermostat for single-element tank
You cannot use single-element thermostat for dual-element tank, unless tank is being rewired for redundant and simultaneous operation.
Wiring illustrations for single element water heater:
American thermostat                    American thermostat wiring
See Larger 240 Volt single                            See Larger 120 Volt single
Basic wiring for changing 240 volt water heater to 120 volt
Why do this? Breaker panel is overtaxed. The 240 volt breaker went bad and you need water tonight (option would be using the 30 amp dryer breaker). The water heater breaker is 20 amp with 12 gauge wire, so breaker is tripping off. The cost of power is too high most hours when you need hot, and you don't mind longer recovery period before water heater reaches full temperature after each use (option would be use 240 volt timer to heat a full tank during off peak or toggle water heater between voltages using a timer) Resources: Toggle water heater between voltages using a timer. Off peak water heater wiring  Home generator that doesn't produce enough power to run heater. Resources: Connect heater to generator   Toggle water heater between voltages using a transfer switch

Changing from 240V to 120V will NOT work on water heaters that require specific voltage such as Solar-glycol heaters, AO Smith-American-etc energy smart, or hybrid electric water heaters. Resources: Review Energy Smart     Review hybrid water heaters
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 for various reasons, but it will work either way, and no codes are violated with either choice.
Wire colors vary by brand of water heater, but basically all residential water heater wiring follows same pattern, unless tank was altered or manufactured for simultaneous or off-peak function etc.
How to wire thermostats
Thermostats are mechanical, and are not powered by electricity, so they work with any household 120-240 volt .... and commercial installation up to 480 volt:  How thermostats work
Instructions: Move wires to single-pole breaker will change water heater from 240Volt to 120Volt
120Volt is slower recovery (heats 1/4 as fast, or 5-8 gallons per hour), and good for homes with low consumption, or consumption that is spaced farther apart ... giving heater time to reheat tank.
Another strategy for faster heating is to install elements rated for 120 volt.

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 ... as long as elements are rated for same of more voltage. If 240 volt element is connected to commercial 277-480 volts, the 240 volt element will instantly burn out. Change element to correct voltage.

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.
Resources:
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
240 volt water heater circuitCautions and general instructions for changing 240 volt heater to 120 volt.
Big wires on main breaker are still Hot when main breaker is OFF.
When main breaker is OFF, then all small breakers are OFF and safe to work on.
Use only solid copper #12 and #10 wires ... if stranded wire is used, then connect stranded to short piece of solid copper and cover with twist on wire connector ... and put solid copper wire under screw plate on breaker and Neutral busbar. Always tighten screws and twist on connectors very tight.
Change wiring from 240 volt to 120 volt
Fig-1 shows typical 240V water heater circuit.
Two Hot wires connect to circuit breaker
Ground wire connects to Ground busbar

Fig-2 shows conversion to 120V:
Move black wire
from 240V breaker to 120Volt circuit breaker rated for correct amps.
30 amp breakers and 10 gauge wire run cooler with less heat loss. Circuit is more efficient, and breaker box lasts longer ... so you can use a 20 amp single breaker, or a 30 amp single breaker because the orange wire is 10 gauge. If the wire is yellow, then wire is for 20 amp breaker only... do use 30 amp breaker and yeallow 20 amp wire..

Move white wire from 240V breaker to Neutral busbar where ground wire connects. If White is not long enough, then buy short length of 10-2 or 12-12 sheathed cable, and take out length of white wire. Join white wires with twist on wire connector. Use only solid copper for #12 and #10 wires.

Modern breaker boxes have separate Neutral busbar where white wires are connected ... while illustration shows both Neutral and ground busbars on same side of box for purpose of illustration, the modern breaker box has Neutral and ground busbars on separate sides of box.
Always connect ground wire onto the ground busbar ... and white Neutral on the Neutral busbar. Water heater must be grounded for safety.
Resources:
Basic 240Volt water heater circuit
How to replace circuit breaker
How to install subpanel
240 volt 4500 watt elements 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.
Resources: Toggle water heater between voltages using a timer   Off peak water heater wiring
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
Resource:
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 element that is rated 240 volt 4500 watt to 277 volt or 480 volt, and elements burn hotter and burn out
   Connect element that is rated 120 volt 1500 watt 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 element that is rated 240 volt 4500 watt to 208 volt or 120 volt, and elements burn cooler and heat less hot water per hour
   Connect element that is rated 240 volt 4500 watt to 120 volt, and element burns 1/4 power and heats at 1125 watts. Good for off-peak or generator.
Resources:
How to replace element
Connect water heater to generator
Low watt density Change elements If 240 volt 4500 watt water heater is connected to 120 volt, then change elements to 120 volt... this will heat water faster
Buy: 120 volt:
1000 watt 120 volt minimum 8" tank diameter
1500 watt 120 volt minimum 8' tank diameter
1650 watt 120 volt 7.5" minimum
1750 watt 120 volt 9" minimum
2000 watt 120 volt 9" minimum
120 Volt elements 
circuit breakers are warm Circuit breaker check up
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 elements 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
Resource:
How to wire 240 volt water heater for 120 volt generator
Toggle water heater between voltages using a transfer switch
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.
Resources
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 ordinary water heater

Buy:
Leviton 3033 switch at Amazon
30 amp 3-way switch
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
Resources:
How to wire T106 timer
All Intermatic timers

Buy:
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
Buy
2-pole 30 amp non-fusable safety switch/ indoor / power cut-off
2 pole 60 amp non-fusable / outdoor box/ at Amazon

Resource:
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
Multimeter: for testing voltage and continuity etc
Buy
 Multimeters at Amazon
Continuity tester at Amazon
Timers can be wired to toggle water heater between 120V and 240V
GM40 timer
Mechanical
Intermatic GM40 series
Intermatic GM40AVE
Digital
GM40AVE
GMXFM1
Et70215 timer
Digital
ET70000 series
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.


Resources:
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 to Intermatic WHQ timer Tork DTU40 timer 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 thermostat 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 thermos 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.
Resource
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.
water heater circuitLarger image
How to toggle between under counter water heater and dishwasher

Same wiring for either 120 or 240 volt loads
Code permits 15 or 20 amp switch on a 20 amp breaker ... as long as switch is rated for same voltage and more amps than Load (anything that consumes power is Load).
Use only approved 600 volt, solid copper wire under screw terminals. Never use extension cord for permanent household wiring.

Objective: Either the dishwasher has power or the under-counter water heater has power. But neither at same time. Why? Because safe maximum amps on 20 amp breaker is 80% or 16 amps ... while dishwasher and water heater together consume 23 amps.
Do not install 30 amp circuit breaker unless wire is also increased in size from 12 ga to 10 gauge. Color code for wire

How to wire: Incoming wire from breaker has 2 wires. If voltage is 120, then the white Neutral wire is never switched on-off. Connect white Neutral wire to each appliance.
Black Hot wire is switched on-off. Connect Hot wire to COM terminal on the 3-way switch (dark or different color screw). Then run a Hot wire to each appliance from the other two screws on switched.

Heavier amp loads, or more voltage, such as 30 amp 240 volt water heater, use a 30 amp 3-way switch (safe max 23 amps).
Other options, for higher amperage loads and motor loads (such as irrigation pumps, shop tools etc), include using a switch (or timer) to toggle loads with 30-40 amp open frame relay.
Buy 30 amp 3-way:
Leviton 3033 switch at Amazon
30 amp 3-way switch
Dishwashers at Amazon
Resource:
How to wire open frame relay

How to install gas water heater

How to install gas water heater

9 ways to save with water heater

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Clean sediment from tank
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box timers Resource:
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