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AssuredElectrical, Master Electrician
Category: Electrical
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Experience:  Contractor-42+ Years in the ElectricalTrade
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This is a question engineers. What is the difference between

Customer Question

This is a question for electrical engineers. What is the difference between the split phase 240V that we get in the US (where 2 120V are combined to give 240V) and single phase 240V (where this a single 240V hot) that folks living in Europe/Australia get? I would like to know for example why would a split phase 240V washing machine made for the US market won't work in 240V elecrtrical outlet in the UK. Thank you.
Submitted: 1 year ago.
Category: Electrical
Expert:  AssuredElectrical replied 1 year ago.

Welcome. My name is ***** ***** would be glad to assist.

US power is not split phase, it is referenced as single phase also.

The 2 power sources are derived differently from the power stations generators.

The thing to understand is this:

In the US, there are 2 wires, that measured to ground or neutral will have 120 volts on them.

Then measured between those same 2, you will get 240 volts, which its the combination of the two.

Elsewhere in most of the rest of the world, you have 230 volts, which is derived form one single wire measured to ground or neutral.

The neutral, is an ungrounded conductor which carries the same current as the hot wires. It returns the current back to the originating transformer.

Power flows out on the hot, returns back on the neutral, so it essentially is a circle in the power supply.

The problem with US made appliances like dryers, ovens etc, is that the electronic circuit boards inside them for operating everything, are manufactured to operate off of 120 volts, not 230 or 240 volts.

Everything except motors and heating elements operate off ONE of the hot wires and the neutral, which measure 120 volts.

The motors and heating elements will operate off the 2 hot wires only which combine for 240 volts.

Other countries operating at 230 volts, do not have 120 volts to operate the remainder of the appliances.

So, if one connects a US appliance that operates on 240 volts to a power source of 230 volts in other countries, it will damage everything inside because the voltage is inadequate for them, it is too high.

Another item in them, is still motors, which in the US operate off 60 HZ frequency of the utility supply.

In most other countries with the 230 volts , they operate on 50 hz power.

So, motors will run at a different speed 20 percent high or lower depending which direction.

A 60 hz motor will run 20% slower on 50 hz, so that too can be a problem on some appliances.

Those are the differences, hope the explanation helps, let me know any questions.


Customer: replied 1 year ago.
Let's put the issue of frequency aside and focus on voltage. 240V appliances made for the US market with three pin plugs (2 hot and 1 ground) have all internal components that run on 240V and not 120V. Surely there are also machines which have four prongs and here there are 2 120V hots, 1 neutral and 1 ground and in this configuration some internal components are indeed on 120V.
Here in California single phase 240V is called split single phase, where there are 2 120V hots that combine to make 240V. But this is language and semantics, which is not at issue here.
My question was is there a difference between a single hot 240V (which is stypical in the UK and most of the world) and two 120V (which add to 240V).
Expert:  AssuredElectrical replied 1 year ago.


Just basing your question on the voltage itself, there is NO difference in US 240 from 2 hot wires at 120 volts and the 230 volt with one hot and neutral in other countries.

If you have a heating element that operates at 230 volts, it will operate off either one with no issues. Or electronic items manufactured for 230 volts

I was providing the information because the problems are in other components inside equipment made in North America that actually operate of a different voltage.

If you have piece of equipment that operates off 240 volts only not 120/240 produced, it will operate off most other countries power source as well as long as items inside will not be affected by frequency such as clocks and timers

Customer: replied 1 year ago.
I am not sure if I am convinced nor do I know if you can shed more light on this issue. At the very beginning, I stated that this is a question for electrical engineers and here is why I said that.
The single split phase of 2 120v hots are at different waveforms, i.e. they have a have a half-cycle offset, or 180 degrees, when measured against the neutral wire. In the US with a three wire 240V connection, there are two hots and a ground. The two hots act as neutral for each other. This is very different from a single 240V three wire configuration, where there is a single hot, single neutral and single ground. The single 240V is on the same waveform however, the two hots 120V (that combine to make 240V) are at different wave forms.
As a result of such differences, wiring an appliance that runs on two 120V hots and a ground to run on a single 240v hot, 1 neutal and 1 ground does not seem like a simple matter.
Expert:  AssuredElectrical replied 1 year ago.


I have personally wired some European 230 volt appliances in the US and there is not a problem.

They were cooker units and no motors.

The measurement between the two wires is still 230 volts, that is all that matters. (besides the frequency)

There are even some motors that have dual frequency ratings and will work with the 230 foreign or 230 US.

Had a customer the other day with one

Not much difference than The US 277 volts derived off of 480 supply, it too uses a neutral with one leg at 277 volts.

If frequency was not an issue at all, you could actually wire your home with the type of European receptacles for your all your lighting and appliances and wire those directly to the US breaker panel

They would operate perfectly fine.

I know of some that had made some special cords for customers to do that same thing and allow them to use some of their items which they brought over with them. They wired US 240 volt receptacles and then had a cord with a male to match the US side, a female to mate tot he UK side.

The customer could then use their small appliances and lighting if they wished.

Not so easy for US moving to another country, because the US lighting and appliances are mostly 120 volts, so a transformer is needed.

Even when traveling overseas, the voltage converters do not change any frequency and small items such as hair dryers etc still function well.

All depends on the appliance how much frequency affects the operation.