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How many amps on power lines
Amp rating on power lines
Ampacity of power line

If you draw grid power during a hot day, it costs more to deliver than on a cool day when the grid can run more efficiently.
Wait until cooler times to run HVAC, clothes dryer, other 240 and 120 volt loads.
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
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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.

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Tools kits
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KNIPEX

Telephone cable knife
Low Voltage Mounting Bracket for Telephone
Push on wire connectors

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

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Red 3P connector for 10-14 gauge wire
Lever connectors for stranded wire at Amazon
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
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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.
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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.
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Analog multimeter
Multimeters at Amazon
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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.

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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
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Buy double-pole:
Choose from 15 to 125 amp
Choose from 15 amp to 200 amp
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Double pole GFCI
amp rating on power lines
Resource: See full list of wires and ampacity/ pdf

Table 1
Table 1 shows amp ratings for one type of stranded, bare aluminum conductor exposed to different ambient conditions ... 77°F (25°C) to 104°F (40°C) with sun and wind conditions. 

Direct sun causes more heat on the power line, increasing resistance on the aluminum conductor, and reducing the total amp capacity (ampacity) of power line.
Wind has a cooling effect, and so ampacity on power line goes up.
The table shows that Heat works against electric transmission and distribution.

Volts and amps
Amperage is the current of electrons that is being pushed through the matrix, or atomic structure, of a conductive material by voltage.
Voltage is the force that is pushing the electrons (measured in amps) along the power line. Voltage remains relatively steady, while amperage rises and falls depending on demand from end users. Resource: Read about power generations
For example, when more businesses are open, and all the lights are on, the voltage stays the same, but amperage flowing on power lines goes up. As businesses begin to close at end of day, and lights are turned off, then voltage still remains the same, but the amperage starts to fall. Voltage doesn't change throughout the day or night, except for brief surge events caused by large inductive loads, lightning strikes etc.

Resistance and heat
Conductive materials, like aluminum power lines (conductors), always offer resistance to the movement of electrons. This is true of all materials.
Each type of material (aluminum, steel, rubber, wood etc) offers different amounts of resistance to the movement of electrons, with metals like aluminum, steel, copper etc being good conductors because they offer less resistance than insulating materials like rubber, wood and air.
Resistance is like friction that works to stop the movement of electrons ... but when electrons are getting pushed (or forced) through the material by voltage, the friction causes heat.
As more electrons are getting pushed along the aluminum wire, then the higher the resistance against that movement ... and the higher the resistance, the higher the heat caused by friction.
If heat on the power line exceeds capacity, then breakers and fuses (overcurrent protection) located at substations or at individual service poles can trip off.

General parameters for choosing a conductor
To solve the problem of heat, the power company must install a power line that has the correct amp capacity (ampacity) to meet the heat caused by flow of amperage during peak demand, and also meet the expected ambient weather conditions that effect power line ampacity.
This illustrates the challenge faced by grid managers as more electricity is consumed because of economic growth while worldwide temperatures are rising.
Resources:
Power line design .pdf
Power generation: from power plant to end user

The grid is a balance of cost and function
Aluminum is chosen for power lines because it is lightweight, strong, relatively inexpensive, workable within a wide range of temperatures, abundant, durable, and resistant to deterioration when exposed to weather ... additionally, aluminum is a conductive metal with low resistance against the movement of electrons (measured in ohms) ....   this makes aluminum and aluminum alloy conductors the best choice for transmission and distribution lines.

Other metals, such as copper, silver and steel are also used as electric conductors.
Steel is a good conductor ... it is much stronger, but much heavier than aluminum. Steel alloys are used for smaller power lines ... for areas with low demand that require many miles of low-cost distribution line. Steel alloy is also used for guy wires (to support poles), and as a core for many types of aluminum power lines. Using a steel core adds strength to long spans of aluminum power lines. However steel is not used for larger power lines because of weight. Steel is much heavier than aluminum. The poles would have to be set closer together, and poles engineered for for higher loads. This would increase costs.
Copper and silver are also good conductors, but heavier, more expensive and not as strong as aluminum. Copper and silver are too heavy and too weak for long spans of wire that are needed for economic transmission and distribution of electricity.
Copper conductors are used for ground wires located on each power pole. Copper is used for household wiring because copper will not expand and contract as much as aluminum ... making copper easier to install and safer than using aluminum wire inside homes and businesses.
Silver is soft and expensive, but considered very reliable for conducting electricity, and is used primarily for electronic circuits.
ResourceDifference between single-phase and 3-phase

kcmil from row 2, Table 1
1 kcmil = 0.5067 square millimeters. A mil is 1/1000 inch, so 266.8 kcmil wire is 266.8/1000th of an inch = .26" or about 1/4" diameter
Typical distribution line might be 900 kcmil or about 7/8" diameter.
amps on power lines
Chart above shows amp rating for one type of 37 strand bare aluminum alloy wire that is among the commonly used distribution lines is about 7/8" diameter.
The line can carry 500-1000 amps depending on ambient weather conditions. Cooler temperatures, clouds, and wind help lower resistance, so the voltage can push more electrons (amperage) through the conductor matrix. Photo taken during installation of power lines. NEVER touch a power line without 100% certainty the line is not carrying electricity.

Single-phase and 3-phase Current or amperage draw from power lines
The current (I) is inversely proportional to both voltage (E) and number of turns on the transformer's primary and secondary windings. E volts N turns I amps (amps is current or flow of electrons).
Resource: Single-phase transformer explained

Single-phase
If primary volts E1 are 7200 volts on the distribution wire. Primary volts is the volt rating of power company line that distributes power to home.
 The secondary volts E2 for household single-phase service is 240 volts. Secondary volts are the volts that go from transformer to the household breaker box, or service panel. Resource: From power pole to breaker box

Now lets; suppose the main breaker is 250 amps then Iis 250 amps, and the maximum amount that the breaker box can supply for household usage is 250 amps. If the draw is greater than 250 amps, the main breaker will trip off.
 
With residential single-phase transformer, the turns ratio is 30:1. We know this because incoming voltage from distribution line is 7200 volts, and voltage supplied to house is 240 volts. Calculate the turns ratio and it's 30:1

So primary amperage (I1) can be calculated: for 250 amp by dividing 250 by 30 = 8 amps. This means the 7200 volt primary line must be able to deliver 8 amps to the primary coil on the transformer ...  but only during maximum usage of household amperage (which would be rare).

Voltage remains unchanged, except for brief surges and anomalies ... so voltage is relatively steady 7200 on the primary side and steady on the 240 volts on the secondary side ... and voltage remains steady no matter how many amps are pulled by the household.
Significant voltage drop does not occur during ordinary residential usage because all electric circuits are wired in parallel, not in series. The means each power pole, light or outlet on a circuit breaker receives generally the same voltage. For example, every outlet in the home receives same 120 volts, no matter many loads are plugged in and turned on.. Only the amps vary, with more amps (or current) flowing when a load is on.

Since electricity is dynamic, and delivered on demand, then 8 amps would be consumed off the primary coil of the transformer only when the home was using the maximum 250 amps ...  for example if home has whole house tankless pulling 120 amps, plus the 23 amp clothes dryer, two 40 amp air conditioners, the 50 amp oven and 25 amp stove top .... the usage would be 295 amps. The 250 amp main breaker in household panel would be trip off, and home might need to downsize usage, switch to heat pump water heater, and stagger air conditioner usage, or install 300+ amp service.

Since the effect of usage at one home is multiplied when a distribution line supplies power to 1000s of homes and businesses, I recommend downsizing usage to ensure the grid remain stable and operable for all folks.

Compare the same amp draw for 3-phase
Primary volts E1 are the same 7200 volts, because the distribution line carries power to both residential and commercial services.
With commercial 3-phase, 3 Hot wires and 1 Neutral are pulled from the 3 hot distribution lines. With residential single-phase, 1 Hot line and a Neutral are pulled from the 3 hot distribution lines. Difference between single-phase and 3-phase
Let's suppose the main breaker at the 3-phase commercial panel is 250 amps so E2 is 250. So the main breaker are same for both residential single-phase example and commercial 3-phase example.
But let's change the secondary voltage at the commercial service E2 to 480 volts commonly found in a commercial 3-phase service. The turns ratio would be 15:1.
This means primary amperage I1 can be calculated: 250 amp divided by 15 = 16 amps. So the 7200 volt primary line must be able to deliver 16 amps to the primary coil.
Each leg of the 3-phase circuit pulls 16 amps, from 3 separate wires at staggered times as the generator rotates. Unlike single-phase that pulls 8 amps from 1 of the 3 Hot wires.
Overall, the effect of higher amp draw results in more power, more kVA or Kilo Volt Amps or Kilowatts.
Kva is a static number used to compare amount of power (watts) delivered to HVAC, motors etc. Kva is not to be confused with Kwh, which a measure of billable consumption of watts of (power).

Difference between single-phase and 3-phase
power transformer
Power transformer.
Other parts include bushings, tap changers, power cable connectors, gas-operated relays, thermometers, relief devices, dehydrating breathers, oil level indicators, and other controls.
LPTs (larger power transformer) found at generating station or regional substation have capacity rating greater than or equal to 100 MVA
Power transformer is much smaller and found at local substations.

Transformers are rated by voltage, and by how fast they cool after heavy demand period.
Extra high voltage (EHV), 345 to 765 kilovolts (kV);
High voltage, 115 to 230 kV;
Medium voltage, 34.5 to 115 kV; and
Distribution voltage, 2.5 to 35 kV.... kV is kilovolts or volts x 1000

power transformerLarger image
Power transformer at local substation

Transformers are designed to step-up or step-down voltage on the transmission and distribution lines, and to provide electrical isolation between the primary windings (coils) and the secondary windings located inside transformer.

Each time the voltage is raised or lowered, the amperage is affected. Basic formula: Volts x amps = watts shows that volts and amps are inversely proportional. When volts are raised, amps are lowered.
Wires with 500,000 volts have low amps and low heat which is good for long-distance transmission. But the switchgear and wiring for 345,000-500,000 etc volts is too large, expensive and dangerous for use inside home and business.

Using transformers, the power company changes volt-amp ratio to accomplish different objectives. The result is households and businesses receive low volt, high amp power. It works nicely because 120-240 household voltage can be safely controlled by small switches, relays, cell phone chargers etc contained within steel and plastic enclosures, while the amperage (heat) is controlled by circuit breakers and then distributed to outlets, switches, dryer etc using correctly sized wire to match amp rating of breaker.
Chart on left shows Transformer kV and  MVA ratings.
Incoming and outgoing power lines are installed to carry specific voltage.
kV is kilovolts ... each kilovolt is 1000 volts.
So 230Kv power line carries 230,000 volts on the primary side, and the 300MVA transformer reduces voltage to 115kV on secondary side.

Power transformers are rated by power or wattage.
MVA is mega volt amps .... volts x amps x 1,000,000
Volts x amps = watts (power)
So 300MVA transformer can deliver maximum 300 million watts of power.
Read .pdf manual

So if a 230kV power line, delivers 230,000 volts to a power transformer that produce up to 300,000,000 watts ... then divide to get approximate amp flow = 1304 amps on the power line.
Power line might be 2500-3000 kcmil (1/1000 circular mil) or 2.0-2.4" diameter.

Not recommended to use more than one ampere per one square millimeter of the aluminum (1 A / 1 mm2).
kcmil = 0.5067 square millimeters. A mil is 1/1000 inch. A wire 200 mils in diameter is 40 MCM. MCM is generally used for very large-diameter wire.
The reason for this is the power loss. If the resistance (dissipation) is getting higher the active power is increased significantly.
This means that higher resistance increases power losses
Oil Type Transformers
Single-phase and three-phase transformers for the range above 16 kVA and up to 72.5 kV.
These units are designed for power centers, substations and networks; also for pad-mounts.
They are used in public distribution systems, commercial buildings and industrial complexes.
For the range 30 kVA to 30 MVA with primary operating voltages up to 41.5 kV and secondary
operating voltages up to 36 kV. These units are designed for operation in difficult conditions
– environmental contamination, fire hazard, high humidity or extreme climates.
161/13.8/13.8 kV,
56/28/28 MVA
∆I SinΦ (Circulating current)
 ∆I SinΦ (S) (circulating current principal for different KVA/MVA ratings of
transformer)
220/66 kV, 50 & 100 MVA

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

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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.  
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15 amp GFCI
20 amp GFCI
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Basic electric book
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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.
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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
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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.

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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

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

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

Terminals

Terminals

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Crimping tool kit
Blue for 16-14 wire
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Ratcheting Crimper

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Push on wire connectors

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

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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
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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
6x6x4 pull box
6" Pull box
Junction boxes for conduit and wiring
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Bud industries 6x6x4 best value/ no KO
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