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What Size Ground for 200 Amp Service? (Explained)

You might be wondering what size ground wire you need when installing a new electrical service. Your answer to this question will vary based on the type of service you’re installing and the voltage of the electricity. 

For 200-amp service, here is a guide to help you determine what size ground wire you need.

Ground size for 200 amp service

A 200-amp service requires copper conductors of #4 AWG or aluminum or copper-clad aluminum ground wires of #2 AWG. GFCIs should be sized twice as large as the current load. The GFCI must handle at least 100 amps of current if your electrical equipment draws 50 amps.

Additionally, you should always use a ground fault circuit interrupter (GFCI) when inspecting and testing your electrical system. Electrical fires can cause serious injury to you and your family if there is no GFCI installed.

The National Electrical Code (NEC) requires all electrical equipment and ground conductors entering any structure to have grounding electrode systems. Listed below are the sizes and requirements for different types of groundings.

Bare/Earth ground:

For 200-amp service, #4 AWG copper conductors are perfect. It cannot be less than #6 AWG. Use the same size grounded receptacle with #4 AWG metal ground wire. Ground electrode systems consist of a grounding conductor and the equipment they serve.

As a grounding conductor, #4 AWG copper conductors can be used without being damaged by aggressive soils and corrosive atmospheres in which they may be buried.

Aluminum ground:

A ground fault circuit interrupter (GFCI) must be rated at 200 amps at a minimum. The grounding electrode system must be sized as a #2 AWG exposed wire if you have a metal grounding receptacle with an aluminum sheath. 

That means you can go no larger than #2 AWG for 200-amp service. There is a no smaller size that conducts electricity and still meets the safety requirements of a GFCI than #2 AWG. A wire with a diameter of 1 or 3 AWG will not meet all of the safety requirements for a GFCI.

Equipment ground:

For equipment grounds, #6 AWG is the minimum and #4 AWG is the maximum. An equipment grounding conductor or electrode must be attached to the building structure directly to connect equipment grounds. 

The minimum size for a service entrance ground electrode is #6 AWG because it has the lowest resistance. The #4 AWG is not strong enough to carry the necessary current through equipment.

Ufer ground:

A 200-amp feeder needs 4 AWG ufer grounding conductors. Ufer ground is allowed when there is no equipment grounding conductor available and the builder determines that the absence of one does not pose a safety hazard. A building’s air-conditioning unit is powered by this feeder. 

It could be used as the ground return if the building had an equipment grounding conductor. Due to the lack of a grounding conductor in this situation, 4 AWG copper wire will be used to provide a safe connection between the service entrance and the AC unit.

Copper ground:

A copper ground wire of #4 AWG can handle 200 amps. To ensure a safe connection, use #4 or heavier gauge wire for connection. For service entrance ground electrodes, copper wire with a 4 AWG diameter has the lowest resistance of all ground wires. 

Moreover, it can handle any potential issue that may arise when power is fed to an AC unit.

Water ground:

A water ground connection is also an option for a service entrance. It is best to use the #6 AWG wire since it has the lowest resistance and can carry a large amount of current. 

With a water ground, you can connect directly to your home’s plumbing system without having to run an extra cable.

200 AMP ground wire size for 3 phase service

Three types of copper wire are required for a 200-amp electrical service: #2/0 AWG copper wire, #4/0 AWG aluminum, or copper-clad wire if it is run inside a three-phase circuit

In the case of a copper service of 200 amps, it is not necessary to use an equipment grounding conductor (GndCnt) to ground the equipment to the ground.

When connecting outdoor lighting and other high-current loads, it is often necessary to use a 200 AMP ground wire size for three-phase service. For most applications, this size of motor can handle a maximum current of 400 amps, so it should be able to handle all your current needs.

It is certainly a good idea to use a ground wire of #2/0 AWG if you are using aluminum or copper-clad wire and want to avoid electrical hazards. You can do this by using a 3″ conduit (or shorter) at the service entrance and installing a GndCnt at the entrance.

How do I calculate ground cable size?

Earthing conductors carry electrical fault current to the ground. Using our earthing size calculator, you can determine the exact size of earthing conductors required in AWG.

Choose wire material:

The type of wire you choose depends on the design of your circuit and the environment in which it will be used. 

Typically, #2/0 AWG copper wire is sufficient for outdoor applications, while heavier gauge wire may be needed for applications requiring higher current carrying capacity. It is important to remember the constant numbers of the materials. 

A copper wire has 205 constants, an aluminum wire has 125 constants, and a galvanized wire has 80 constants.

Find out what service you use for amps:

Your circuit design and the environment in which it will be used determine the amps service you need. Through the use of design formulas, the calculator automatically calculates the amps required.

Find Fault Clearing Times:

After a short-circuit or open neutral occurs, the fault clearing time is the period it takes for the current through your circuit to drop to 75% of its original value. A fault clearance time is an important consideration when selecting a suitable ground wire size and how to install it.

Do the calculation:

To determine the ground cable size, you must use a simple formula. The formula is as follows.

= (Amp service – Actual Use) / Fault Clearing Time

For example:

For example, if your amp service is 200 and the actual use is 70, then you would need a ground cable size of #4/0 AWG.

How to install ground rods for 200 amp service?

Installing ground rods for 200-amp services requires measuring the depth of the soil and ensuring that there are no obstructions such as rocks. The following is a step-by-step guide to help you install ground rods for 200-amp service.

Find the ground rod diameter:

The diameter of the ground rod is the length of the metal pole that will be buried in the ground. You should match the ground rod size to the soil depth and grade of your property.

Cut the needed amount of ground rod sleeve:

As the name suggests, a ground rod sleeve is a piece of metal that will be used to connect the ground rod to the soil. Ideally, the sleeve should be long enough to reach the end of the hole so that it reaches the bottom of your hole as well.

Connect ground rod sleeve and soil:

There should be a waterproof connector used to connect the soil to the ground rod, such as epoxy or a block of cement used to bond the soil to the ground rod. 

Lay ground rod in a hole:

Ensure that the ground rod extends at least 10 inches below the surface of the soil.

Connect green wiring clamp:

Green wiring clamps are used to connect ground wires to the ground rod’s metal grounding lug. Using a wrench, it is recommended that the ground wire be tightened onto the metal lug of the grounding system.

Make sure the connection is secure:

It is recommended to secure the ground wire to the ground rod using a lock washer and nut as shown in the picture below. The last step is to secure the connection between the wiring clamp and the grounding metal lug on the end of the ground rod by using a cable tie.

Additional Tips:

On the ground rod, it is also important to install a lightning arrestor. When lightning strikes your home, a lightning arrestor helps prevent electrical damage.

Final Thoughts

To conclude, copper wire #4 AWG is a suitable choice for a 200-amp service. For aluminum, however, use #2 AWG. Calculate the actual size by multiplying the amp service minus the actual use by the time it takes to clear the fault. Depending on the type of grounding, the size may vary.