240V power is extremely handy. You can power up your welder, electric car, and a 50-amp RV.
But what if what you are looking for at the moment is not 240v? What if you need a 120V receptacle on a dedicated circuit?
This post will review how to take 120V off a 240V circuit, including:
- Power
- Phase
- Breaker
- Wire
- Adapter
Knowing that a 240v circuit is just two 120v wires, you can get power by tapping into the electrical box or a wide array of adapters and extensions.
Table of Contents
Power
Getting 120V power from a 240 volt circuit is a simple task. Both are ac voltage, and no transformer is needed.
It’s no coincidence that a 240 volt circuit is exactly twice of a 120 volt circuit. This is because house electrical services are comprised of two 120V power lines. And when you put those two lines together with a double pole breaker, you get a higher voltage of 240 volts.
The question now is how to get just one of the power lines so you can use it as 120V receptacle. Knowing how a 240V is wired will help us figure out how to get just 120V.
Phase
Home electrical service is single phase. That means one hot wire provides power, with one neutral wire. This makes going for 120v single phase from 240v as simple as getting one of the hot wires for your 120v power.
Circuit Breaker
We discussed that a 240V breaker is a double pole breaker. That means that two breakers are acting as one breaker. You need a double pole breaker for 240v power because each breaker is connected to one of the 120v hot wires in the panel. A regular 120V breaker is considered a single pole breaker.
Your main breaker panel has two columns with several circuit breakers aligned in each row. These circuit breakers usually range from 20 amp to 30 amp breakers. Each alternating breaker picks up one wire (or leg) of your service. Each leg is a 120V circuit, and when put together with a double pole breaker, it gives you 240 volt power.
Wire
Now that we know how two 120V wires generate 240V, let’s understand how to take that power needed. There are two easy ways to do this, direct wire or adapters. Let’s explore how to do this and the advantage and disadvantages of each method.
Direct Wire
As always, when working with electrical wiring, ensure breakers are off and no power is going to your receptacle before you work on it. Besides just turning off a breaker, I encourage you to get a multimeter and double-check the receptacle to make sure. This is 240v and can pack a punch, so be extra cautious.
The direct wire method is just that, it’s wiring into your junction box to get 120v power. When you open up the electrical outlet box of a 240V receptacle, you will see a total of 4 wires:
- Copper Wire. This is your ground wire. Ground goes to the panel, then down to a ground rod for extra protection.
- Red Wire. This is one of the hot wires. It has 120V power.
- Black Wire. This is the other hot wire. It is also 120V power.
- White Wire. This is the neutral wire.
Since a 120V receptacle is one hot wire, one neutral wire, and the ground wire, we can tap into and use only those needed wires. You can choose either the red or the black wire. It doesn’t matter as both are 120V power.
To get a 120V receptacle connected, cap off the extra 120V wire not used (again, this can be the red or black wire). Then wire the 120V receptacle as usual with one hot wire, one neutral, and one ground. Remember that the 240V wiring was probably thicker than usual, around 6 or 8 gauge. Whereas a typical 20 Amp 120V only needs to be 12 gauge. The wire may be too thick for the 120v receptacle. If that is the case, you will need to pigtail with a 12 gauge wire so it will connect with the 120V plug.
Also, typical receptacle plugs are 15amps. Going from 240V to now 120V, you should be able to get a dedicated 20 amp 120V receptacle.
Advantage
The advantage of this method is that you now have a 120V receptacle that is permanently and securely installed. You can plug in and out as easily as any other outlet.
Disadvantage
The main disadvantage is that you are permanently (until you rewire) changing a 240v outlet into a 120v. If you ever need to return to the 240v receptacle, you must undo your wiring and reconnect. If you want to use this outlet for 240v and 120v at various times, I suggest you look at the next option, adapters.
Adapter
When looking for a versatile outlet that you can use as needed between a 240V outlet and a 120 volt outlet, the use of adapters may be your best bet. The adapters allow you to interchange between the different voltages as often as you want.
An adapter from 240v to 120v works on the simple notion that it just takes one of the two hot wires. So no magic or transformers are used when using an adapter to get 120 v. It is an outlet with a small extension cord to a 120v female end.
The good news is that there is a full array of adapters that you can get. Whether you have an RV outlet, a dryer outlet, or a 30 amp 240V locking outlet, you can find the adapter that will plug into that with an adapter to a 120volt plug.
Advantage
Versatility is the main advantage of using adapters. You plug into your 240V receptacle and can get 120V power. And when you want 240V back, unplug, and you are back to the higher voltage.
Disadvantage
The disadvantage is that you have the added cost of the adapters, usually around $30. Not too bad of a cost considering you can easily switch between the different voltages.
And the other disadvantage is that you have this adapter with an extension cord. It may be difficult to work around tight spaces.
For more information on 50 amp service, visit the installing a 50 amp outlet.
Final Thoughts
Knowing that 240v service at your breaker box is just two 120v wires makes getting the lower voltage you want simple. You have two options to get 120V: direct wire from the receptacle box by connecting to only one hot wire. Or you can get adapters that cap the second hot wire to give you the 120V outlet you want.
Tony is an avid camper and RV traveler. He fell in love with camping on his first RV trip with his wife over 25 years ago. Tony loves sharing lessons learned and tips about RV maintenance and safe traveling.
