Home Generator

[dennishoddy]

Hopefully @dennishoddy will chime in quickly, but pay attention to the bit about the transfer switch. Get that part wrong, and your generator will backfeed the line and potentially kill someone.

Yes, potentially. In reality, no lineman will touch a line that has not been isolated and verified unenergized from both ends they are working on. The safety record of 99.999% of linemen is exemplary. There is that one aw-crap though that gets through the cracks occasionally.
A homeowner that doesn't isolate the home is more likely to waste wattage back feeding their neighbors homes, and possibly having a phase short if they are reversed by someone that isn't familiar with electrical standards.

 

[Fredkrueger100]

I’m definitely getting a licensed electrician to do it.

 

[Dave70968]

Yes, potentially. In reality, no lineman will touch a line that has not been isolated and verified unenergized from both ends they are working on. The safety record of 99.999% of linemen is exemplary. There is that one aw-crap though that gets through the cracks occasionally.
A homeowner that doesn't isolate the home is more likely to waste wattage back feeding their neighbors homes, and possibly having a phase short if they are reversed by someone that isn't familiar with electrical standards.

Might be best in a PM to avoid derailing the thread, but can you explain a phase short--which I think I understand--and how it can occur in a single- or split-phase system, which I don't?

 

[dennishoddy]

Might be best in a PM to avoid derailing the thread, but can you explain a phase short--which I think I understand--and how it can occur in a single- or split-phase system, which I don't?

All modern homes are fed with 230 volt single phase. Two 120v phases that are opposed and a neutral. Ground rod outside the home for the safety ground.
I've never understood the "single phase" wording as if you contact the opposing phases, you have a short. Split phase is a better term to describe the commercial power coming into the home.

Edit:

 

[TerryMiller]

Not that I have a need for anything right now, considering that I live in our RV, but Dennis' comment about 230 volt makes me wonder if such "portable" generators can handle 230 volts. Someone might have the idea of washing and drying clothes and if it is an electric dryer, it would likely be 230 volt. Again, an electrician would be a critical consideration in any case with a generator.

 

[dennishoddy]

Not that I have a need for anything right now, considering that I live in our RV, but Dennis' comment about 230 volt makes me wonder if such "portable" generators can handle 230 volts. Someone might have the idea of washing and drying clothes and if it is an electric dryer, it would likely be 230 volt. Again, an electrician would be a critical consideration in any case with a generator.

I have a small portable generator that is 1000 watts for our RV in case of an emergency. It is only 120V.
Most bigger units have 230 volt "split phase" outlets to run what is needed. 230 volt appliances actually run about 1/2 the amperage of 120 volt appliances. Ohm's law.

 

[Dave70968]

All modern homes are fed with 230 volt single phase. Two 120v phases that are opposed and a neutral. Ground rod outside the home for the safety ground.
I've never understood the "single phase" wording as if you contact the opposing phases, you have a short. Split phase is a better term to describe the commercial power coming into the home.

Edit:

That's what I understand as "split:" a 240V phase with a tap in the middle, yielding a pair of 120V circuits exactly 180° out of phase; it doesn't quite look that way on the graph, but if you take either side against the middle, it's 120V sine wave, and if you take one side against the other, it's 240V sine wave.

My understanding of a "phase short" is closer to a three-phase, with one shorted against the next (and no, I don't understand quite how to convert between delta and wye configurations, which complicates that definition--it makes perfect sense in a wye, but none at all in a delta).

Again, I'm leery of derailing the original thread; would you mind writing a new thread with a primer so those of us interested can have this discussion?

 

[dennishoddy]

That's what I understand as "split:" a 240V phase with a tap in the middle, yielding a pair of 120V circuits exactly 180° out of phase; it doesn't quite look that way on the graph, but if you take either side against the middle, it's 120V sine wave, and if you take one side against the other, it's 240V sine wave.

My understanding of a "phase short" is closer to a three-phase, with one shorted against the next (and no, I don't understand quite how to convert between delta and wye configurations, which complicates that definition--it makes perfect sense in a wye, but none at all in a delta).

Again, I'm leery of derailing the original thread; would you mind writing a new thread with a primer so those of us interested can have this discussion?

The graph was just an example of how two phases oppose each other without getting into detail of how one is above zero volts in its cycle while the other phase is below zero volts which constitutes a short.
If I haven't thrown them away, I've got hand written notes on how to troubleshoot and diagnose three phase motors in the wye and Delta configurations. Went through my files awhile back and tossed a bunch of history since retiring. Still have the engineering books though that was used for reference purposes. I'm not an engineer, just a tech that used them for reference.

 

[Dave70968]

The graph was just an example of how two phases oppose each other without getting into detail of how one is above zero volts in its cycle while the other phase is below zero volts which constitutes a short.
If I haven't thrown them away, I've got hand written notes on how to troubleshoot and diagnose three phase motors in the wye and Delta configurations. Went through my files awhile back and tossed a bunch of history since retiring. Still have the engineering books though that was used for reference purposes. I'm not an engineer, just a tech that used them for reference.

I'd love to see them at some point. My first major was EE, and I still wish I knew more about it.

 

[MacFromOK]

FWIW, any power fed back into the grid must be in phase with the grid.

Otherwise, the grid will destroy your power source, because its power is massive compared to whatever you may have.

It's similar to directly connecting two motors at different RPMs, where one has 1000 hp and the other has 1 hp.

Something's gotta give.