Originally Posted by buffa98

240 degrees out of phase. Depending on which of the 2 legs you are getting. A,B,and C.

A-B=240V(120 Degrees apart)

A-C=240V(240 Dgrees apart)

B-C=240V(120 Degrees apart)

Seeing 99% of houses use single phase capacitor start motors the degrees between the phases really dont matter.

Originally Posted by kerry

Is there a lineman here? In our neighborhood the electricity is carried on poles. 3 wires and up on top of the poles now and again are three big fuses. There's an insulator and about a 14" fuse that carries power around it. Periodically, squirrels will short out the wires at a transformer or something and one of these fuses pops. It makes a big bang like a shotgun blast. You can tell the problem because the fuse hangs down. On my block, when one fuse pops, everyone loses all their electricity. I have a rental property 4 blocks away. When one of the fuses pops on that block, only about half the electricity goes out in the houses. It's kind of a PIA because tenants (and homeowners) then think it's an internal problem to the house since some electricity works. Why the difference between the two blocks?

Originally Posted by Brian Carlton

Not possible.

Any single line is 120V to neutral.

The only way to get 240 is for the two hot lines to be 180 degree out of phase.

Also, if any of the two lines were not 180 out of phase, you must have the neutral. Many 240V appliances don't have a neutral (my compressor as an example).

Originally Posted by buffa98

Use this picture to follow what I am saying


Homes for the most part use a single phase power. With the wires coming to the home there are 2 insulated and one Common or ground. When One of the 2 loses its path only half of the circuts in that panel will work( Just like BC said) There are 2 sides to a transformer. When the suplly side loses a leg your house goes dark. If the downstream side loses a leg only one of the three "loads" on the transformer loses everything While the other 2 lose half. I hope this helps.

Originally Posted by spdrun

208V (2 120V legs 120 deg apart) isn't all that uncommon.

Originally Posted by buffa98

Very possible. There has to be a nuetral point to finish the circut back to ground. I will bet a dollar to a donut the plug on you compressor has 3 prongs on it. 2 hot(240V) and one ground or commom.
In a 3 phase transmission line the phases are 120 degrees apart. See the pic from post @744PM.
PS I work in power generation. If the phase were to Slip that far apart bad things happen at the generator.

Originally Posted by Brian Carlton

Yes, 120V 3 phase produces exactly what you stated but with 208V across any of the hot leads.

A residence has only single phase. It's referrred to as "split single phase" as you get 240V across the two hot leads and 120V from either hot lead to the neutral.

Originally Posted by Brian Carlton

You're referring to 120V 3 phase power. Agreed..........quite common..........but not in a residence.

Originally Posted by buffa98

Very possible. There has to be a nuetral point to finish the circut back to ground. I will bet a dollar to a donut the plug on you compressor has 3 prongs on it. 2 hot(240V) and one ground or commom.
In a 3 phase transmission line the phases are 120 degrees apart. See the pic from post @744PM.
PS I work in power generation. If the phase were to Slip that far apart bad things happen at the generator.

Originally Posted by buffa98

What voltage you get across the 2 "hots" is dependant on the type of transformer. delta delta.delta y. y y. Center tap nuetral etc etc.

My line voltage has been as high as 265 and 144 on a single.

Which is another nreason a lot of the big appliances now are marked 240\208.

Sorry for the hijack.

Kerry- the fuses between the upper lines and the transformer are for the 7200V distribution lines. Between the transformer and the houe are to protect the transformer from damage.(240V)

Originally Posted by Brian Carlton

Not possible. The compressor does not have a neutral to bring the circuit back to ground and it does not need to have a neutral because the two hot legs are exactly 180 degrees out of phase. There is a typical ground lug...........not to be confused by a neutral. The ground can be eliminated and the compressor will operate perfectly fine.

Yes, in a three phase transmission, the phases are 120 degrees apart.........but not in a residence.

You may work in power generation, but the split single phase common in residences is clearly foreign to you.

Originally Posted by buffa98

I'm not going to argue. The laws of AC electicity do not ever allow for 180 phase shift. Can not happen because of the 120V in you home is stepped down from either 345KV,138KV down to 69KV to the switchyards for the final step down. Which are all 120 degrees apart.

Originally Posted by Brian Carlton

It doesn't exactly make sense to me either. But, you cannot get 240V from the two hot leads unless they are 180 out of phase. I can assure you that the voltage is 240V from the two hot leads and 120V from either hot lead to the neutral.

If you can explain this phenomena with three phase power, please do so.

Originally Posted by buffa98

How much time do you have?