Replies

1. 
   user-6001446 | Feb 12, 2023 04:19pm | #1

   I’ve looked this up when studying up to become familiar enough with modifying electric circuits to avoid burning anything down or killing myself as I thought that somehow this might matter, but it turns out it pretty much does not. It was confusing to me because folks refer to “220”all the time but you see in electric specs, eg for breaker switches, 240v. I believe it used to vary more and was 220v supply to residences at one time in the past in US. It varies around the world. Now, the US is standardized (mostly I think…. apparently several years ago New York was still different and had 208v) to be 240v for residential or 120v per each hot wire with two hots and a ground for residential power supply. From the service panel 120v (what my Dad always called 110, he was a farmer not an electrician) outlets and switches are connected to only one of the 120v service feeds, 240v (our “220v” outlets in our wood shops) are connected to both hot wires. I believe 240v is a more efficient way to transport power which is how it got to be standard but that might not be the technically correct answer.

1. 
   esch5995 | Feb 12, 2023 04:44pm | #4

   208v is the voltage across 2 legs of 3-phase 120v wye connected power supply and not seen in residential wiring. You can see this in high-rise commercial buildings because it can supply multiples of 120v circuits but it is inadequate to operate 240v single phase devices because each 120v leg is supplied by a separate generator each with a separate phase connecting two legs results in 208v not the 240v you would have in a single phase circuit.

2. 
   gulfstar | Feb 12, 2023 04:19pm | #2

   Well more like 120, 240 V. It all started with 100V, a nice round number but moved to 110 and now 120 for efficiency reasons, the change is slow to accommodate the obsolescence of the power distribution equipment and I would not be surprised that in 20 years or so, we will be at 250/125V.

3. 
   esch5995 | Feb 12, 2023 04:30pm | #3

   The actual standard in the US is 240v for residential and light commercial supply. This can be can be split into individual legs of 120v each at the breaker panel of individual buildings. Due to voltage loss over transmission lines and other variances between utilities the American grid can supply anywhere between 240v to 220v which again can be split into separate legs equal to half of the supply voltage so 220v supply will actually have 110v standard outlets. These variances are all built into the electric code and any device rated for 120v will operate fine on 115v or 110v.

4. 
   john_c2 | Feb 12, 2023 05:45pm | #5

   220, 221. Whatever it takes.

1. 
   oxmach | Feb 12, 2023 06:47pm | #6

   Ha! Nicely done Mr.

5. 
   suburbanguy | Feb 12, 2023 11:43pm | #7

   While the 60 Hz frequency is kept very accurate, voltage can fluctuate with demand. In a brownout the voltage drops very low, and consequently the current draw will increase to maintain a motor's horsepower. This can shorten the life of motors.