120v Inverter/Shore Power switch or relay?

[smckean (Tosca)]

The current comes into the house on the hot lead and returns to the transformer via the neutral.

I'm afraid this is not so either.

Electric power comes to a house on 3 wires: 2 hots, and a neutral. The voltage between the 2 hots is 240v; and between either hot and the neutral is 120v (there are other voltages possible depending on the transformer, but this is normal at least in residential settings). Each of the 2 hots go to one or the other of the 2 busbars in the panel. Branch circuits peel off from one busbar in the panel or the other along with a neutral making a 120v circuit. You are right in one respect, in the branch circuits, power flows into the circuit via the hot and flows back via the neutral, but this is not so for the service conductors that energize the panel (the 2 hots and 1 neutral from your meter). One of the objectives of wiring a building is to balance the load on the 2 sides of the panel. If the loads are perfectly balanced (let's say each side of the panel has a 50 amp "turned on" load), then no current will flow in the service neutral. OTOH, if one side of the panel is drawing 40 amps and the other 50 amps, then 10 amps will flow on the neutral back to the transformer. This is perhaps easier to see if we talk about the 240v circuits in a home (stoves, dryers, etc). These circuits have no neutral, but just the 2 hots. Every electron that flows down one of the hots flows back on the other hot. So all the power in a 240v circuit flows from/to the transformer via the 2 hots and the neutral isn't involved at all. If the loads on the 2 sides of the panel for 120v circuits are exactly equal, no current flows on the neutral back to the pole just like is so for a 240v circuit.

This will be my last post on this thread.

P.S. Describing AC circuits can be confusing since we tend to think/speak as if circuits were all DC; that is, we say current flows down one conductor and back on the other. This is not really the case. In actuality, current is oscillating back and forth 60 times per second on the 2 hots in a sinusoidal pattern. In the branch circuits the power is oscillating back and forth on its hot and on its neutral. The 2 hots coming from the transformer are in opposite phase (i.e., 180°), and therefore at the panel the 2 busbars are also in opposite phase. Therefore, the flow on the neutral bar from the branch circuits on one side of the panel cancels the flow on the neutral bar from the branch circuits on the other side of the panel. If the current on each set of these two sets of branch circuits is exactly the same, then no current flows on the neutral since the current is the same but 180° out of phase, so in that situation no current flows back to the transformer on the service neutral.

 

[B95054]

Absolutely correct and shame on me for attempting to oversimplify the flow of current into the house. There is still the issue of surges and how they are handled through the ground. But I will leave that subject alone. Suffice to say that leaving the ground unconnected as somebody posted above is a bad idea ( maybe that is just what I should have said in the first place and not over complicated things). I’ll leave it alone now too.