I just finished explaining generator wiring to a friend who has no electrical skills. He is looking to buy a generator since hurricane season is coming up. I figured I would share the info here as well for people looking to buy one.
One thing I saw when reading reviews were people complaining that their generator is tripping its built in breakers well below the rated output on the generator. This comes from the fact that they bought a 110/220 generator and how the windings are tied together.
Most residential portable generators are wired from the factory with Parallel 110V windings and are not set up to be switched easily from this setup.
This means you have (2) 110V windings, each able to generate half of the total power output. Therefore, you must run two cords from the generator to run multiple items in the house and get full power out of it.
Since Watts = Volts X Amps:
Using a 3200 watt generator as an example
When you buy a 110/220 volt generator, it usually has a 220V outlet with breaker sized for the full output of the generator. That will be 220 Volts and a 14 or 15 amp breaker supplying that max amperage to each leg of the 220.
(220 X 15 = 3300 watts)
It will also have (2) 110V outlets, each with a breaker sized for ONE HALF of the generators full output, also 14 to 15 amps.
(110 X 15 = 1650 watts)
My friend wants one for his parents house to run a refrigerator, window unit, some lights, and some fans. So he will need to run the fridge, a light, and a fan from one 110V outlet on its own breaker at the unit and then run the window unit, a light and a fan from the other 110V outlet on its own breaker at the unit.
He’s a computer science major, so the best analogy I could give him is that it is like partitioning a hard drive into two separate, equally sized pieces, then not understanding why only half the data will fit on each partition even though the hard drive says it can hold twice that amount. Hopefully, that can help some other people visualize it.
It is possible to rewire the generator to series windings and get the full 30 amps from one 110V outlet, but then you lose your 220V capability, you void all kinds of warranties and risk letting the magic smoke out of plenty of items.
Hope this helps anyone who might be shopping for a generator in the near future.