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Why you need ground wire

To the homeowner, the purpose of ground wire is to protect people, circuits, and property from short circuits and arc failures (loose wire spark) by providing unobstructed path to earth .... and protect the circuit breaker and wire during a short circuit by absorbing voltage.

To the grid, the function of ground wires and ground rods at each home, business, pole, substation, transmission tower, all bonded together by the Neutral wire back to power plant, is to provide an array of earth connections that stabilize the electrical system ... absorbing lightning, power surges, voltages irregularities .... the earth absorbs voltage and 'balances the equation.' ... and that's why people get electrocuted, because they become the pathway for electricity to reach earth.
... and that's why you stand on dry boards when working on electricity outdoors, and make sure you have Ground fault on the circuit so it will interpret and cut-off the rush of power going down the wire before the person becomes a pathway to earth.
What is electricity
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If your appliance has 3-prong grounded plug, then that appliance can have short circuit that travels to the outer shell of appliance, and this short can kill you if appliance is not grounded.

That's why UL rated appliances are important, and the US has national electric code.
The ground wire is connected to outer shell of appliance, and travels back to main breaker box, and then to ground rod outside home.

For example water heater recirculation pump has 3-prong plug. If recirculation pump gets a short circuit, then the ground wire will carry amperage safely away from pump, and away from water pipes.
Remember the recirculation pump is connected to your bath and shower.

If the ground fault is slight and not large, then breaker will NOT trip, and ground wire releases the small current into ground rod located outside house near main panel ... and it is generally safe to touch recirculation pump.

If the ground fault is large enough, it will begin to pull more current through shell of appliance and into ground wire and down to the ground rod, and that current will overheat wire at breaker, and breaker will trip. It will happen very quickly, but until breaker is tripped, the live current is available on the outer shell and can still kill you.

If you do not have ground wire, and recirculation has large short, and you touch recirculation pump while standing on bare ground, or while touching water pipe, or leaning into metal washing machine, or taking shower etc... you can fry like a fish, as current finds easiest path down to ground.

This is why grounding is important.
IF you have GFCI or arc-fault breaker on the circuit, then the slightest ground will trip breaker before it becomes dangerous.
Bond solar panel to ground rod

Ground wire

All phone, satellite, pool equipment, solar systems and electric panels must be grounded. Check local electric codes.
What does this mean? Drive ground rod 8-10 feet into soil. Bond #6-8 bare copper wire to ground rod and to solar panels and pipes on roof.
Do NOT ground electric system to water pipes. Ground must be connected to ground rod. Stray current corrosion can cause pipes to deteriorate. Uncertain bond to ground because of plastic pipes.

Ground rod and clamps at Amazon
Bonding lugs

Bond all ground wires together to help prevent surge & lightning damage

Bonding all grounds together will help prevent damage from lightning strikes beyond 100' away...
Strong lightning strikes within 100 feet must be handled by lightning rod
Local code requires bonding: this includes all ground rods for satellite, TV, phone, solar, electric panel, subpanels (within 100 feet) etc must be connected together and bonded to main electric panel ground rod driven into soil at correct depth to meet local code. Consult local electrician.
Codes for grounding depth vary: loose rocky dry soils are less conductive than dense wet soils
No system other than lightning rods will protect against direct lightning strike or strike within 100 feet.
Move indoors and do not stay on roof, or move metal ladders, or touch anything made of metal when lightning is within 1 mile or can be heard or seen.
Best basic electric book
Basic electric book/ very detailed
Grounding workbook
surge vs ground block

Surge vs ground

Generally all types surge protectors must be grounded. But not all grounding is surge protection.
A ground wire will NOT protect equipment from overvoltage .... unless the power exceeds device or wire rating, or causes failure so that electricity arcs to the box and follows ground wire to ground rod.
Surge protection is needed to protect equipment from overvoltage.
For example motors will cause voltage spikes etc that can harm other appliances.
Surge protection suppresses or absorbs overvoltage and anomalies in electric power. In some cases, the overvoltage is redirected to the ground wire, so the ground wire is a necessary part of surge protection.

100' feet away for lighting is the rule of thumb.
Anything closer than 100', and nothing can protect against the voltage.
Beyond 100' and proper grounding can help redirect the surge into the ground.
Proper grounding requires all boxes and devices to be connected with a ground wire that is adequately connected to a ground rod that is at sufficient depth to reach permanently damp soil, or an array of ground rods with sufficient low resistance to meet local code, and that all grounds rods are bonded together with a common wire. For example if you have a ground rod for satellite TV and separate ground rod for electricity, they should be connected with a common ground wire of bare copper or green-coated copper wire.
However the ground wire will not protect electronics etc from damage from lightning ... for this you need a surge protector, suppressor, arrestor ... and possibly a lightning arrestor
... and generally, the surge protection needs to be grounded.
Note: surge protection wears out over time ... because it is consumed by the continuous small and large surge that is typical with electric wire and devices.
Bond motor to ground

Outdoor Pump or pump in wet location ... must be bonded... or grounded... directly to ground rod... in addition to regular ground wire coming from electric service

Ground all electrical devices, and all household grounds together and bond to main breaker panel and to ground rod

Do not ground to water pipe: Make sure ground is connected to ground rod

Water heaters and metal water pipes corrode with stray current corrosion.
Modern pex water lines are not affected, and cannot be used as a ground.
When installing new water heater, water pipe, doing repairs on plumbing, installing new electric service etc... check that all electric is connected to dedicated ground wire that is bonded to outdoor ground rod
Bonded means steel electric panel enclosure must be directly connected to local ground rod
Outdoor control panel and pool pump must be bonded to ground rod located at point of installation/ local codes vary so consult local electrician/ some codes may allow bonding to metal conduit that enters the soil at point of installation... but stray current corrosion can cause deterioration of this conduit/ codes vary for grounding for many reasons, including because different soils offer different resistivity to grounding/ for example dense wet soils conduct to ground better than loose dry rocky soils

Ground rod and clamps at Amazon
Bonding lugs

Why ground is important
Basic household wiring
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The reason I have not posted a page on transfer switches is because of the huge number of resources already posed on the topic...

I think the generator produces a neutral off the coil, and so that neutral must be supported. They probably want the neutral separated inside the box for reasons of code and safety...

BUT ... I do not have the engineering expertise to adequately explain why neutral and ground must be treated differently, yet are apparently the same thing. (I've seen the mathematical formulas, but they are above my pay grade).

Neutral and ground are confusing under any circumstance.
According to books I've read: System neutral/ service neutral runs throughout the electric grid ... from every home, across every pole, through every substation, back to the power plant...  to 'stabilize' the entire grid.
The ground wire is attached to the neutral at each step along the way ... and I assume this is to protect each individual installation (pole, electric box, transformer etc) while the neutral 'stabilizes' the entire system.

Electricity always wants to flow back into the ground soil... and will do so with high speed and damaging effect without correctly designed safeguards.
One book talked about the neutral-ground system being able to safely route overvoltages or shorts to the ground soil without arcing or bolts of electricity jumping from the hot wires to nearest ground and causing fires and damage.
Since any material can conduct electricity if voltages are high enough, it is probably required to provide a quick and safe route to soil using ground wire, before voltages increase to point of arcing over to the nearest object.

By code... the neutral cannot be used as a ground... nor ground as a neutral.
As a general rule for household wiring... the neutral wire has to be as large as the hot wire... so that the neutral wire can support the same amperage as the hot. While the ground wire can be a smaller wire, but is normally the same size.
Why? I do not know that answer at this juncture.

Here are simplified resources that match my pay grade:
The ground wire is a direct and certain path into soil.
While the Neutral wire is not as direct.
Probably the neutral is not direct because it is also to complete 120V or 277V circuit, or 230-240 Volt circuits in other countries, and neutrals are not always twisted together to make a direct path..
.. Example 120 volt outlet, one neutral can be connected using quick connect located on back, and another neutral connected to the screw terminal located on side.
Another example... gfci... the neutral travels through metering device before connecting back to other neutrals.
Contrast all bare copper grounds are twisted together, or screwed straight to the metal shell of a motor/ appliance ... and do not travel through outlets, or other obstacles before reaching the ground rod.
Codes for grounding vary by local soil.
Certain soils are less conductive/ rocky soils/ dry soils, so copper ground rods have to be deeper or other variations. Tests and formulas determine conductivity of soil.

Electric safety

Cleanliness, Oil grease carbon dust can accumulate on electronics and electrical equipment
Do not work on electricity with oxygen or other explosive vapors such as paint, gasoline, varnish
Close paint containers, store in separate, well-ventilated room

Always de-energize circuit
Do not apply water to electrical fire
CO2 fire extinguisher
Do not use foam fire extinguishers/ foam is conductive
Some electronic parts give off toxic fumes
In event of fire, de-energize equipment, use CO2 extinguisher, ventilate room, avoid breathing smoke
Do not touch burned equipment with bare hands

Always use non-conductive tools
Be careful when soldering that extra solder does not drip on other parts causing potential short
Protect power cords from sharp edges/ Replace worn power cords
Always cut power to tool that is jammed

Electrical danger death and injury from shock falls burns flying objects
Muscle spasm causing person to clasp the electric device
Knock loose with 2x4 or belt, rope, coat, blanket
Do not touch person or you will become electrified

Tight clothes only
Do not wear loose clothes on sleeve, neck, legs, chest or abdominal area

Shock from electricity

All voltages are dangerous. 120 volt is most common voltage for death from electrocution.
Person suffering from electric voltage:
Lay them down. Keep from moving
Check if they are breathing.
Continue artificial respiration
No stimulants or opiates because the heart might be affected by electric shock

Electric burn can cause pain, shock, open wounds
Wash minor wounds with soap clean water apply cold water
Deep open bleeding wounds, sterile compress, immediately call medial personnel

Equipment can have more than one power supply
Each box should be powered by one breaker but sometimes not
120 v is sometimes considered safe it is not
Install safety switch within clear view of equipment
Make sure switch is in open or safety position before working on equipment.
Note location of high voltage lines
Be cautions around incoming power lines when painting
use insulated ladders
Electric workbench should have insulated mat
Use insulated gloves
Remove jewelry rings watch metal before working on power

Use one hand only when possible
Post warning signs
Do not reach into enclosures
circuit breaker

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Water heater is tripping breaker
How to replace circuit breaker
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Can AC breaker be used for DC breaker
How to reset circuit breaker
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Why you need ground wire
Match breaker and wire size
How to wire subpanel
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How to wire safety switch
How to wire whole house surge protector
Transfer switch
Use twist lock plug for extension cord that plugs into compressor

Install 20 or 30 amp as needed.
X Y terminals go to either Hot,
W is always Neutral
G is ground
These are standard markings for 240 volt plugs and outlets.
Connect X to one hot busbar inside the transfer sawitch, connec6t Y to other hot busbar, ground and Neutral to respective terminals
Leviton 2711/ 125-250 volt/ 20-30 amp/ 3 pole
How to wire subpanel
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30 amp safety cut off
Safety switch
Fusable pull out
Fusable pull-out

Pull-out disconnect -or- Non-fusable Safety cut off 

for outdoor installation:

Locate cut-off next to electric equipment ... or short reach away... within sight of appliance.
Purpose to protect anyone working on electricity ... so person knows power is OFF, and power cannot accidently be turned ON.

How to wire safety switch

Residential information: varies by state and locale
Non-fusable safety switch required on outdoor installations, and high-voltage indoor applications such as 90 amp tankless electric water heater where breaker box not in plain sight of equipment.
Fusable vrs non-fusable: Non-fusable means there is no breaker or fuse inside the cut-off box. Non fusable is manually-operated on-off switch for safety.
Fusable means there is a fuse or breaker that trips when detecting high heat.

How to wire safety switch
Pullout Disconnect at Amazon
Fusable pullout disconnect
2-pole 30 amp fusable safety switch/ power cut-off
2-pole 60 amp non-fusable safety switch
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Electricity leaves power plant What is 3-phase electric: power plant to end user

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How to install electric meter on water heater
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Read how to convert AC water heater to DC/ high voltage
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How many Kwh to heat water
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