70A Wire Size Explanation (Breaker, Ground, Service) | PortablePowerGuides (2023)

If you're looking to upgrade your circuit breaker to 70 amps, you're probably wondering if the wires can stay the same. However, you cannot answer this question without first determining the correct wire size for a 70A circuit breaker. Knowing the wire size that can handle 70 amps can help you determine whether or not your existing wiring will match that wire size. If not, consider upgrading the wiring in your home before installing a new breaker. Otherwise, the wrong wire size will burn your house.

What size wire is needed for 70 amps?

The best wire size for 70 amps is 4AWG. This wire size can change depending on the voltage required, ambient temperature, voltage drop, distance, location and material used.

70A cable size chart

Volt wie 70 AmpereMaximum distanceAWG(copper)Aluminium
120V95 feet4AWG2AWG
240V191 feet4AWG2AWG
480V383 feet4AWG2AWG
Volt wie 70 AmpereMaximum distanceAWG(copper)Aluminium
120V120 feet3AWG1 AWG
240V241 feet3AWG1 AWG
480V483 feet3AWG1 AWG
Volt wie 70 AmpereMaximum distanceAWG(copper)Aluminium
120V152 feet2AWG1/0AWG
240V302 feet2AWG1/0AWG
480V609 feet3AWG1/0AWG

Let's check the wire size for 3 phase 150 feet apart.

Wire size for 70 amp three phase

Volt wie 70 AmpereMaximum distanceAWG(copper)Aluminium
120V150 feet2AWG1/0WG
240V150 feet4AWG2AWG
480V150 feet4AWG2AWG

Related post:

  • 50A (120, 240, 480V) wire size chart with single phase, three phase
  • 80A wire size (breaker, ground, service) explained

What wire size for a 70 amp breaker?

For a 70 amp breaker you will need 4 gauge wire, but only if the conductors are copper. If you prefer the cheaper option, buy 2AWG aluminum wire. Also, match each breaker to the correct wire size. Otherwise the threads will melt. The circuit breaker must protect the cables.

For example, 6AWG is suitable for 60A breaker. If you force the cables to carry more than 60 amps, the 60 amp circuit breaker will trip, preventing the cables from overheating.

But what if the wires are only 10AWG? 10 gauge wire can handle 35 to 40 amps. They will overheat and melt long before the 60 amp circuit breaker trips.

(Video) Electrical Wire Size Calculator. is there an easy way?

Therefore, you must carefully select the circuit breaker. Your choice affects the security of your home.

The NEC encourages consumers to limit charging to80 percentcircuit capacity. But that's no excuse for using fine yarn.Some devices double or even triple their power consumption when they start up.

You need a gauge that can handle that tip,For this reason, most electricians use 4AWG copper wire rated at 70 amps. You know that 4-gauge conductors can carry 70 to 85 amps of current without overheating. That leaves a lot of room for error.

You can also usefio 6 THHNbecause it can take 55 - 70 amps. But 4AWG is still better, especially for people who want stable power supplyRun welders, drills and other heavy tools.

What wire size for a 70 amp subpanel?

4AWG is the best wire size for a 70A subpanel (2AWG for aluminum).

I want you to consider factors like thatAmbient temperature, material, installation method and more.I would like you to limit that tooVoltage drop to 3 percent. Equally important is the thermal resistance of the soil (if you plan to bury the cable).

These other factors only come into play if you are tempted to experiment with lighter gauge cables.

Wire size for 70A duty

The best wire size for a 70 amp service is 4AWG. This is the safest option, especially if the conductors are copper. If you prefer aluminum, you will need a thicker handle.

Watch the temperature. 4AWG is perfect at 140 degrees F. But you can get a thicker wire if you want to leave room in the line for an extension. 4AWG is not the loudest gauge out there. 1AWG can take up to 145 amps.

(Video) Sizing Equipment Grounding Conductor, 2017 NEC - [250.122] (3min:49sec)

It's better to buy a thicker wire than necessary just in case the load exceeds the circuit breaker capacity and it doesn't trip. Small diameter conductors cause performance problems due to voltage drop.

Some of your devices have stopped working because the cable cannot transmit the minimum power required. But that's the best-case scenario. If you have a sizable charge, you can start a fire.

Think of the distance. Long cables are more likely to overheat as they have a higher resistance.

Ground wire size for 70 amps

The ground wire size for 70A is 4 AWG. You can use the same gauge for the hot, neutral, and ground wires. The ground wire is a defensive component that conducts electricity to earth when a malfunction occurs.

You can also use a ground wire that is larger than any other wire as it has lower resistance. However, you cannot use a smaller thread. It will overheat and melt.

What does NEC say about this?

NEC expects consumers to combine 70A circuit breakers with 4 AWG.

Wire strength60˚C

This table shows the different ampere ratings for 4-gauge wire with respect to variables like material rating and temperature.

This table may confuse some laypeople. He connected 4AWG rated at 70, 85, 95, 55, 65, and 75 amps. What is it? Can you pair 4 gauge wire with all those amp ratings?

Why does the current change? The table answers all of these questions.

(Video) What size wire do I buy for my electrical service panel? The NEC answers...

The amplifier performance of a given wire size will change with temperature and material.

Copper has a higher conductivity than aluminum. Therefore, it can transmit more power without overheating. Overheating is a critical issue.

The table shows that 4AWG is the best size for 70 amps. But technically you can also connect 6AWG, 8AWG and even 10AWG wire to a 70A load. The conductors carry the electricity you need.

However, this practice is not safe. Small cables have greater resistance than their wider counterparts. So a 10 AWG wire with a 70A load is more likely to catch fire.

A 4-gauge wire can handle 70 amps, but only if the conductors are copper. Aluminum is less conductive than copper, which in turn means it has a lower current carrying capacity.

A 4AWG aluminum wire can carry a maximum of 55 amps and only at the temperature specified in the chart (140 degrees F). Manufacturers make cable that can operate at higher temperature ratings, so the table shows 4AWG copper conductors capable of carrying 85A at 167 degrees F.

You cannot use amperage alone to select wire size. A professional will encourage you to consider material and temperature. Don't be so quick to discard aluminum just because copper is a better conductor.

Copper is superior to aluminum in most areas. However, copper conductors cost more money. Look at your budget. Can you afford copper? Most homeowners use copper when distances are short.

But if you want to cover several hundred meters, you might want to reconsider.

(Video) What size wire do I need for 100 amp service?

Aluminum is not a bad alternative. Ultimately, you can still get the same results by using a better gauge aluminum cable. 4AWG won't cut it, not for 70 amps. However, you can use 2AWG aluminum wire.

How do I determine the correct wire size for 70 amps?

You don't need to calculate wire size for 70 amps. The NEC has already carried out these calculations. You can just use your spreadsheets.

They show wire sizes in AWG and MM and corresponding ampere ratings. The NEC tables also show amperage values ​​for different materials and temperature values.

Visit NEC's online platform to find the right cable size for your situation. If you don't know how to account for factors like distance and temperature,talk to an experienced electrician, especially if you want the wire to travel a long distance. An electrician can calculate the voltage drop.

What kind of wire should I use? Does it matter?

Yes, material matters. The current carrying capacity of each wire size varies with the material. Copper has higher amperage ratings than aluminum. This is because copper is more conductive. But aluminum is cheaper and lighter.

Your choice depends on your budget. Copper can certainly carry more power, but you can get similar results with a larger gauge aluminum cable.

Does distance matter? 70A VS distance

The distance affects the display. A longer distance requires a higher meter because you have to compensate for an increasing resistance. You must calculate the voltage drop before proceeding. Find a meter that does not allow the voltage drop to exceed 3%. A 4AWG copper wire is sufficient for distances found in most residential environments.

Does voltage matter at 70 amps?

At 70 amps, the voltage doesn't matter. If you examine most charts that list cable sizes and amplifier ratings, you'll find that they rarely mention voltage. This is because voltage does not affect wire size.

Wire size is important for current because the diameter of a conductor affects how much current it can carry without overheating. Voltage is not included in this equation.

(Video) How to wire and properly ground a 30 Amp sub-panel

If your dealer asks about the voltage, they're probably concerned about the insulation. Current shapes wire size while voltage controls insulation.


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