50 amp is one of the most common amperage for which we need a gauge, breaker or a wire. Major questions regarding 50 amp wire include:
- What is the wire size for 50 amps 240 volts? (50 amp wire gauge; NEC code applies)
- Wire size for a 50 amp sub panel 100 feet away? (Here we have to account for the voltage loss)
- What electrical equipment can you run with 50 amp wire? (wattage will depend on voltage)
Let’s clear up the AWG wire gauge size first:
If you check the wire gauge ampacity chart here, you can see that there are 3 AWG wire sizes that have ampacity near 50 amps. these:
- 8 AWG wires with 50A ampacity (very small).
- 6 AWG Wires With 65A Ampacity (Perfect).
- 4 AWG wires (too big) with 85A ampacity.
Now, choosing 8 AWG wire with 50A ampacity seems like a good choice as a 50 amp wire size, doesn’t it? However, in almost all cases, Correct 50 amp wire size is With 6 AWG 65A Ampacity, This is true for any voltage; 12V, 110V, 115V, 120V, 220V, 240V, you name it.
Why is it like this?
We have to account for the 80% breaker rating rule set by the National Electrical Code (NEC) regulations. The maximum loading for any branch circuit is 80% of the circuit’s rating for the wire’s capacitance for any given load.
Let’s take a quick look at how you can choose the right AWG gauge wire for 50 amps (or any amps for that matter). Later, we’ll also look at what happens when 6 AWG wire is not enough as a 50 amp wire (due to voltage loss over distance), and what you can run with a 50 amp 110V or 220/240V circuit:
50 amp wire size (using the NEC 80% rule)
You cannot use 50A ampacity wire to make a 50 amp electrical circuit. If you do this, you are likely to fry the circuit.
The 80% rule serves as a safety measure. You should have that extra 20% on top of at least 50A ampacity.
Here’s how you calculate how much capacitance 50 amp wire should have at least:
50 amps. Wire Ampacity for = 50A / 0.8 = 62.5A wire
This means you must use a wire that can handle 62.5A as much as a 50 amp wire. Now, we don’t have a 62.5A wire. The closest wire we have is a 6 AWG wire with 65A ampacity.
pay attention: You can always use a bigger wire but never a smaller wire. For 50 amps, you can use 4 AWG wire with 85A ampacity (a bit overkill but that’s ok), but you can never use 8 AWG wire with 50A ampacity (you will fry the circuit ).
In most cases, 6 AWG is almost perfectly sized wire for a 50 amp breaker. In limited cases, you’ll probably have to use a larger 4 AWG wire. That’s when you have a long circuit and are sending electric current over some distance (100 feet or more).
50 Amp Wire Size 100+ Feet Away (Accounts for Voltage Drop)
Even if you’re sending power through a long distance (eg, a 50 amp sub panel 100 feet away), you’ll need to account for the voltage drop.
A good rule of thumb for voltage drop is:
The voltage drops 20% every 100 feet.
To get the same wattage (power) on the sub panel 100 feet away, you’ll need to increase the amps by 20% (to balance the 20% drop in voltage).
Of course, this means you’re working with more current (more amperes) and you’ll need to choose a larger wire size.
Example: 50 amp wire is typically 6 AWG (we need at least 62.5A and 6 AWG can handle 65A). If you have to power an electrical appliance 100 feet away, you need 20% more amps. Instead of 62.5A, you’re looking at 62.5A × 1.2 = 75A.
In this case, 6 AWG gauge wire with 65 A will not suffice. We need at least 75A. The next wire size that can handle more than 75A is 4 AWG gauge wire. It can handle at 85A and is typically used as a 50 amp wire size for a sub panel 100 feet away.
There are quite a few questions regarding 50 amp and different voltages. Let’s deal with this as well:
What size wire do I need for a 50 amp at 11o-24oV?
A common misconception about 50 amp wire is that we need different wire sizes for different voltages. For example, we don’t need a large (or small) wire size at 110V for 50 amp at 240V for 50 amp.
In all cases (except when we have to account for voltage loss) we use 6 AWG wire for 50 amps.
Now, wire size and amps can be the same. With different voltages, we don’t get different amps; We get different power (wattage).
For example, a 50 amp wire on a 240-volt circuit can handle up to 12,000W of power (this is a very common power setting for RVs). Here’s how you can calculate it:
wattage = Amps × Volts = 50A × 24oV , 12,000W
If you have a 110V circuit, 50 amps will produce 5,500W of power.
We hope the topic of 50 amp wire size is a little more clear now. You can also check out a similar post for: