All ground wires have to meet minimum ampacity criteria. That, of course, is also true of 200 amp ground wire. We are going to look into what size ground wire you need for a 200 amp service. On top of that, we will show you how you can figure out ground wire size for any amp service (50 amp, 100 amp, 200 amp, etc.) yourself.
If you Google ‘what size ground for a 200 amp service’ you will see many different ground wires being thrown around. This includes anything from 0000 AWG, 000 AWG wire, 2 AWG wire, 4 AWG wire, 6 AWG wire, and even something as ridiculous as 8 gauge copper or aluminum wires.
It’s quite hard to see why these recommendations for a minimum ground wire size for 200 amp service vary so much. Even more, it’s quite impossible to understand why such small wires are being thrown around. Especially since we have a clear National Electric Code (NEC) recommendation on what size ground wires you should be using.
Namely, the NEC Article 250, Table 250.66 titled ‘Grounding Electrode Conductor For Alternativing Current Systems’ tells you:
- What size hot copper wire should be grounded by what gauge copper ground wire.
- What size hot aluminum wire should be grounded by what gauge aluminum ground wire.
Both of these copper and aluminum tables include AWG or kcmil (MCM) wires and AWG ground wire pair. However, many times we will ask about the amps exactly. ‘What size ground wire for 200 amp service’ is just such an example. That’s why we need to look at wire ampacities before we can answer which is the right sized wire for 200 amp service.
On top of that, we will also check what size ground wire to use for 200 amp service 50 feet, 100 feet, 150 feet, and 200 feet away (it is not necessarily the same). Here we will have to account for voltage drop due to the distance from the electric-powered unit.
Let’s look at how we can use the NEC Table 250.66 to deduce what size ground wire do you need for a 200 amp service:
200 Amp Ground Wire Size: How To Figure It Out?
If you check the ground wire size Table 250.66 for copper and aluminum wires here, you can see that we already have an idea of what ground wire you need for what size hot wire. However, nothing is said about the ampacity.
Since we are looking for a 200 amp service ground wire size, we have to include the amps. Here is a 3 step-by-step way of figuring out what size ground wire we need for 200 amp service:
- Determine which kind of hot wires you are using: copper or aluminum wires.
- Check the AWG gauge wire chart for the hot wire ampacity rating. We are aiming for 200A ampacity or higher. Here is the copper AWG wire chart and here is the aluminum AWG and kcmil (MCM) wire chart. These are screenshots from both charts for wires that can handle 200 amps or more:
- We see that we have to use 000 (0/3) AWG hot copper wire for 200 amp service, or 0000 (0/4) AWG hot aluminum wire for 200 amp service. Now we pair these hot wires with the ground wires using the NEC Table 250.66 like this:
As you can see from this 3-step process, you need:
- 4 AWG copper ground wire for 200 amp service (at short distances).
- 0 AWG aluminum ground wire for 200 amp service (at short distances).
Now, this is relevant is the hot wire is short.
If you need a 200 amp service 50 feet, 100 feet, 150 feet, or 200 feet away (Example: 200 amp sub-panel 100 feet away), you also need to account for voltage drop. Let’s look at what size ground wire is needed for a 200 amp service 100 feet away as an example:
What Size Ground Wire For 200 Amp Service 50, 100, 150, 200 Feet Away
With longer wires, the voltage drops due to resistance in the wire. If you want to have 200 amps at the end of the 100 feet wire, you might need to start with a hot wire that can handle more than 200 amps. With this thicker hot wire for 200 amp service, you may also need a thicker ground wire.
Voltage drop for single-phase AC and DC current is calculated using this equation:
Voltage Drop = I (Amps) × (2 × Wire Length (Ft) × Wire Resistance (Ohms Per 1000 Ft) / 1000)
Due to the loss of voltage, we need to start with a wire that can handle 205A, 210A, 215A, 220A or so, if we want to provide 200 amp service at a distance.
In this case, the hot wire has to handle more than 200 amps. That’s why we need to use a thicker wire and, as a consequence, we also need to use a thicker ground wire if we want to run a 200 amp service some distance away.
As you can see from the screenshots above, we need:
- 0000 (4/0) AWG copper hot wire with 230A ampacity to deliver 200 amps service at a distance. This wire requires 2 AWG copper ground wire. We see that the copper ground wire size changes from 4 gauge ground wire for short distances to 2 gauge ground wire for longer distances (50, 100, 150, 200 feet).
- 300 kcmil (300 MCM) aluminum hot wire with 230A ampacity to deliver 200 amps service at a distance. This wire requires 0 AWG aluminum ground wire. The same size aluminum ground wire for 200 amp service is used for short and long wire lengths.
As you can see, it’s not all that hard to figure out what size ground wire you need for 200 amp service. Using the cited 3-step process, you can now determine the ground wire size for any amp service.
For 200 amp service we need:
- 4 AWG copper ground wire for short distances and 2 AWG wire copper ground wire for longer distances (50, 100, 150, 200 ft away).
- 0 AWG aluminum ground wire for short distances and 0 AWG wire aluminum ground wire for longer distances (50, 100, 150, 200 ft away).
We hope this adequately explains why these ground wire sizes are need 200 amp service. If you have any questions, our comment section below is always open.
Table of Contents