4-Prong 250 Volt Connections VS 3-Prong 250 Volt Connections

Posted by Christopher Hahn on

In previous weeks, we mentioned that it is impossible to adapt up or down between 125 Volts and 250 Volts. However, you can adapt down to 125 only if the power source is rated as a 125/250 Volts connection. So what factors go into determining if you can step down the voltage?

Let’s start by breaking down the anatomy of each voltage. The amount of voltage in a connection is determined by the number of hot wires being used.

So for a regular household outlet which is typically 125 Volts, there is only one hot wire, one neutral, and one ground. For a NEMA 6-20 outlet, often associated with 250 Volt AC Units, there are two hot wires, no neutral, and one ground.

 Another example is your 50 Amp range outlet and a 50 Amp welder outlet.

A NEMA 14-50 outlet has two hot wires, one neutral, and one ground. This means it is able to make two complete sets of 110 Volts by using one hot, the neutral, and the ground. The NEMA 6-50 welder outlet has two hot wires, no neutral, and one ground, meaning it cannot make two complete sets of 110 Volts. Since it is missing a neutral, it cannot be broken down into two sets of 110 Volts.

It is the presence of neutral or ground, and the number of prongs, that determines if you can adapt down from a 250 Volt connection. Most 3-prong 250 Volt connections do not have either neutral or ground, but 4-prong 250 Volt connections do, allowing you to adapt down to a 125 Volt application.

When a connection is 4-prongs and rated at 125/250 Volts, it is best to refer to it as exactly that. When talking about electrical connections, a lot of people like to just simply say “250 Volts.” While this is correct, it is important to remember that 3-prong connections can also be 250 Volts, which makes a big difference. If you can’t remember 125/250 Volts, then add the number of prongs when talking about 250 Volt connections. That will help us, and other electricians, to diagnose the problem and find a solution.

We offer adapters that can adapt down to 125 Volt connections.

AD1430520 will let you use a regular household plug in a 4-prong dryer outlet. AD1450520 will do the same for a 4-prong range or generator outlet. We even have adapters for 4-prong generator outlets.

The adapters for 4-prong generator outlets can be used to power one, two, or even four household connections.

Since there are two hot wires in a 4-prong generator outlet, the power can be split up into more outlets. You may recognize this topic if you have read about or watched a video based on a previous topic; Power Distribution Units.

If you have any more questions about the differences in voltages, please leave a comment or reach out to us with a text, phone call, or email.

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  • Hello Dean. Does your heater come with a plug at all? Or does one need to be wired on? Please send images of your heater’s plug to me at ac-creative@acconnectors.com. From there, I can see which direction would be best.

    Christopher on
  • I bought a heater manufacturer in the UK, so it is 230v, 13amp, their wiring shows 3 prongs, 1 hot, 1 neutral and the ground, it is 1000kw-2000kw. Do i need to buy a nema 6 20amp 250v plug or can i just buy a UK to USA 125v adapter?

    Dean on
  • Hello Fred. We actually already have an adapter you can use that will save you time and money: https://acworks.com/products/ac-works-adl1420620-locking-adapter-nema-l14-20p-20amp-125-250volt-4-prong-generator-locking-plug-to-nema-6-15-20r-250v-15-20amp-t-blade-adapter?pos=1&_sid=40f5dadf6&ss=r
    L14-20 plugs by themselves can be expensive, and this adapter saves you time with testing and looking for the right cable.

    Christopher on
  • I have a twist lock L14-20 receptacle on a 4000w generator and want to attach the corresponding plug from the generator to a 20A-250 V 3 prong receptacle (NEMA 6-20R) that will allow me plug into this a 250 v heater cord.
    Using a 3 wire pig tail, what terminals on the the L-14 are the 3 wires attached( obviously, green on ground)?

    Fred on

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