I’m not trying to stir up trouble here because I have no intentions whatsoever of using the (original) 220v portion of the circuit for any purpose whatsoever — but I am curious so I will ask.
If I tried to hook a 220v appliance to a receptacle in the 220v section that drew more than 20 amps, that would fry my ground wires (rated for 20 amps) in the 110v section, right? Actually, if so, it might fry any ground wire - even in the established 110v circuit on the other side of the wall because they are sharing #12 wire grounds, right? Again, if so, would the 20 amp sub breaker panel stop this from happening?
Don’t confuse ground and neutral. If there are no malfunctions, a ground wire should spend its entire life with no current ever passing through it, not even for a moment.
OTOH, if there *is *a malfunction the ground wire can find itself conducting thousands of amps. At least until (ideally) a circuit breaker interrupts the flow or (not ideally) something else in the circuit, either feed or ground, melts through.
Conversely, a neutral wire carries the exact same current flow as the hot feed wire(s) do. And needs to be sized accordingly. Ignoring the specifics of your weird split-and-rejoined set-up, you’ll see the hot and neutral wires of anything are the same size. Because they carry the same current.
And to close the loop … Ground wires are sized the same as well since the working assumption is that during a malfunction the circuit breaker/fuse in the system will do its job properly and cut the flow of power before it exceeds the short-term capacity of either the hot feed wire or the emergency return ground wire. An undersized ground wire won’t meet this condition. Instead the undersized ground wire might melt from overcurrent before the circuit breaker reaches its triggering current.
I had an even better Plan C idea this morning. I went into the utility closet to have another good look around. And since it was just at sunrise, I turned on the light to see better.
And then it hit me. The light! There’s already 110V power right there at the switch in the closet! :smack: :smack: :smack:
In the immortal words of Emily Latella … “Never Miiind!!” :smack:
I wasn’t planning on spending the extra bucks for a GFCI Circuit Breaker but that would solve a possible grounding problem, right?
Also, I can’t find a (very) small breaker box - like 2 to 4 circuits.
In days of yore, it was thought that neutral-bonding the chassis on a 240v appliance would be sufficient as a safety ground because the neutral, under normal circumstances, carries no current. (Because the out-of-phase hot wires cancel each other out on the neutral return.)
This has a couple of problems: one is that you can’t always rely on the hot feeds being perfectly balanced, especially if one leg is used for powering 120v control electronics on the appliance. So the neutral could potentially carry a little current under normal circumstances, making the chassis bonded to a current source. Oops. But the main problem was redundancy; something like a water heater will still operate if the neutral becomes disconnected, but now you have no safe return path if a wire should come loose and touch the chassis. So now all metal appliances require a separate safety ground wire which is not to be used as a neutral. (If the 240v appliance does not require 120v, however, you can omit the neutral.)
The other failure mode for a 220 split phase using the neutral as ground is for one phase to go dead. Now the neutral = case ground is carrying 120V. Ouch.
That can happen for a variety of reasons, including one half of the circuit breaker tripping but not the other half. Yes, the switch bats are mechanically connected. But the guts are separate and anything that can fail will fail given enough installation-years.