# 120 Volt or 240 Volt

#### denniswiseman

Bronze Supporter
Hi
Just curious
Looking through posts on the site I see reference's to wiring up for 120volt or 240volt
I know the UK is nomimal 240volt and the USA is 120volt but I don't understand why anyone in the states would want to wire up for 240volt

TFP Guide
It allows you to use smaller wire since the current is less. Power is voltage times current. So if you double the voltage you halve the current.
Also, some motors run more efficiently with 2 phase electricity.

#### denniswiseman

Bronze Supporter
Still confused
So would you need to have 2 phase's at your property to increase to 240
I suspect that isn't normal

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TFP Expert
Standard residential wiring in the US is single phase 220-240v AC 60hz. We have 3 wires coming from the utility pole 2 hot and 1 neutral/ground. Each hot leg has 110-120v potential to ground. The hot (L1) to hot (L2) voltage is 220-240v. All of our standard outlets are 110v. Any high current appliances, like a stove, dryer or pump, are wired for 220v to keep the wire size requirements down. Every time you double voltage you reduce current by half.

#### denniswiseman

Bronze Supporter
That makes more sense to me now but if you add the 2 hot 110-120v surely they must be on different phases because if you add 2 x 110-120v on the same phase you will have 110-120v
Please correct me if I'm wrong as I'm not an electrician but have a basic understanding

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#### Bama Rambler

TFP Expert
In the US the common residential power is split phase so it's essentially two phases 180º apart, so the voltage potential between the two hot legs is double the voltage between each leg and neutral, or commonly referred to as 120/240 volt service.

#### denniswiseman

Bronze Supporter
Thanks everyone
Totally clear now and I won't puzzle about it anymore
Completely different from the UK

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TFP Expert
There is a nice breakdown of standard US residential power HERE. This explains it better than I can and it has pictures.

#### JoyfulNoise

TFP Expert
Platinum Supporter
Let's just be thankful that Nikola Tesla won the argument over Thomas Edison or else the US would be electrified with DC power as opposed to AC power....

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#### JamesW

TFP Expert
AC won because it can be stepped up and down in voltage easier than DC.

High voltage is easier to transmit because it reduces the wire size needed.

Just keep AC away from elephants.

#### pooldv

TFP Expert
Platinum Supporter
They're scared of AC power too?

#### Donldson

TFP Expert
In The Industry
They are ever since Topsy...

#### JamesW

TFP Expert
Edison proved that elephants are adversely affected by AC.

Also, the wing beat frequency of bees is a resonant of 60hz. So, it freaks them out.

#### JoyfulNoise

TFP Expert
Platinum Supporter
Edison proved that elephants are adversely affected by AC.

Also, the wing beat frequency of bees is a resonant of 60hz. So, it freaks them out.
Edison would also kill stray animals with AC electrocution in public demonstrations to "prove" AC was too dangerous. He was in a very heated competition with Tesla & Westinghouse.

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#### pooldv

TFP Expert
Platinum Supporter
Oh, nice. Good thing nobody's ever been killed by DC current. We should switch everyone over.

#### pooldv

TFP Expert
Platinum Supporter
Edison proved that elephants are adversely affected by AC.

Also, the wing beat frequency of bees is a resonant of 60hz. So, it freaks them out.
Do European bee wings run at 50 hz?

#### JamesW

TFP Expert
Do European bee wings run at 50 hz?
Legally, bees are supposed to maintain a wing beat frequency that is a harmonic of the national electrical frequency. In other words, the wing beat frequency should be an integer multiple of the fundamental ac frequency.

However, bees often ignore the rules and do whatever they want.

Bees are critical to human survival. Without bees, humans would starve to death in about a week.

#### CaptainCannonball

Silver Supporter
Let's just be thankful that Nikola Tesla won the argument over Thomas Edison or else the US would be electrified with DC power as opposed to AC power....

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It's funny, I always think about how things would have turned out if AC didn't "win." Would we have a more distributed energy system that didn't rely on huge power lines crossing everywhere one looks? Would it be less vulnerable to attacks in today's world? Would what we now call "alternative" energy be more commonplace? We certainly wouldn't have the economies of scale benefits or the barriers of change. I can't help but think of all the solar panels producing DC electricity that has to be converted to AC and then back to DC for many devices in our home.

One thing is for sure, AC is a fine business model for large energy production that allows for repeat customers Don't think I don't recognize Tesla's brilliance, but it's hard to ignore Westinghouse's (or Edison's) motivations!

oops, that was a little off topic

#### JoyfulNoise

TFP Expert
Platinum Supporter
I'd like to see more concept homes being built that have alternative power sources available - that is, the home has it's own solar PV array built into the design to provide energy to the home during the day and then an electrical system that can switch between the two power sources easily (maybe even add in some battery backup systems in the event of a power loss or utilize natural gas powered backup generators). The home would be wired with both 120/240VAC outlets for the larger home appliances (fridge, big TV's, etc) and a parallel system of wiring for 5/12/24VDC applications (device chargers, computers, etc). There is so much automation and sensor technology available nowadays that it's so sad to see homes being built with the same breaker panels and rotary power meters that debuted in the early 1900's....

and I don't call it "thread hijacking"...I call it "topical evolution"....

#### gwegan

TFP Expert
We are moving more towards a distributed source grid with literally millions of passive essentially solar points producing power. It now appears that over time the main sources of electricity will be very local with the larger plants or sources including batteries both local and regional (pump storage) acting as backup for the local sources. Its much more complex to balance but over time that is where we are going. As the cost for solar drops the big question is going to be how do we build more batteries.