OK I learned something; the official term is "multiwire branch circuit", I didn't even know this was a thing before today. Makes sense, but go figure it's often done for cost cutting.

See section "E3701.5 Multiwire branch circuits" in this draft Florida code book:

http://ecodes.biz/ecodes_support/fr...idential/PDFs/Chapter 37 - Branch Circuit.pdf

 

A pair of 15A 110V outlets that share a neutral and are normally on different phases would potentially put 25A (the generator max) on the shared neutral if I maxed the outlets, probably more than the wires typically used for a 15A oulet would handle safely.

Possible but highly unlikely. Given your limited generator capacity I have doubts you would ever be loading it up to its full 3000 watt capacity and only doing so with just two circuits at the same time.

If you want to put a transformer on the system you certainly can but from my view its a pointless waste of money until an actual problem shows up to justify it.

 

Possible but highly unlikely

While I mainly agree I've also been burned by Murphy far too many times to assume that the possible won't happen exactly when it will hurt the most.

 

While I mainly agree I've also been burned by Murphy far too many times to assume that the possible won't happen exactly when it will hurt the most.

Like when we're running 2 window unit AC units after the hurricane leaves us without power.

 

3 KW isn't enough to power 2 window AC units. It may run them, but it probably won't start them. It's hardly enough to power a refrigerator and a freezer. 3 Kw of power is so miniscule, it isn't even worth considering hooking up to your house wiring. Just buy some 12 gauge extention cords and power essential loads as required.

 

This is a tech site. We can do math.

My, you seem to be just full of these pithy little comments.

 

3 KW isn't enough to power 2 window AC units. It may run them, but it probably won't start them. It's hardly enough to power a refrigerator and a freezer. 3 Kw of power is so miniscule, it isn't even worth considering hooking up to your house wiring. Just buy some 12 gauge extention cords and power essential loads as required.

Our window units are small (5000btu I think) and take about 800w each once they're running, I don't remember what the refrigerator takes but it's less than the AC units. Using our current 4kw unit, when any 2 are running, there is plenty of power left to start the 3rd as well as run a few lights inside and outside the house. After more than 3 total weeks on generator power (1 week after each of the last 3 hurricanes plus various random outages in between) I haven't had 2 try to start simultaneously, or if they did it didn't cause any problems. With the 3kw I'll probably have to be more mindful of turning off lights, etc.. to keep enough headroom available for starting the AC units and fridge.

In contrast, the AC unit in my trailer (15000btu) does take a chunk to start up, and right about 2kw to run. The window units that we install in the house during outages are much smaller.

With it wired directly to your house, not only can you use your lights and small appliances like normal (microwave, computer, internet, ceiling fans, outlets for phone chargers, etc..), but you can also lock up your house and turn the alarm on at night when you're sleeping. So even if you've only got a small amount of power, wiring direct to the house is really nice. Yes generator theft after storms is a problem too, so I keep it chained and have an alarm inside my house that sounds when the generator stops producing power.

 

Our window units are small (5000btu I think) and take about 800w each once they're running,

Air conditioners require about 7X to 10X their run current to start. Even a good 5000 BTU window shaker pulls about 3.5KW for a few tenths of one second to start. If your generator is being successful, it is a much better unit than what I am used to seeing.

 

Our window units are small (5000btu I think) and take about 800w each once they're running, I don't remember what the refrigerator takes but it's less than the AC units

Well then obviously in this real world worst case scenario you are still nowhere near the limits of what a 12 or even 14 ga wire can handle continuously thus once again negating the justification for the transformer.