How an Automatic Transfer Switch Works

[cheesyrollup]

Hi, I'm wanting to install a small solar system to offset my grid usage, but I'm having trouble wrapping my head around automatic transfer switches. Unfortunately, I'm having trouble finding resources outside of individual products or specific installation questions.

I'd like to base my questions on some basic assumptions.

1) Solar system will be about 3kW
2) Loads for the house will range from 500w to 20kw
3) Initially there will be no battery backup
4) The system will be expanded over time to include a larger array and battery backup

Here are a few questions I currently have:

1) Can an ATS use whatever solar is available at the time and then supplement the home's needs with grid power or does it only use solar when solar available is greater than the loads?
2) When the solar available is greater than your load, does the excess solar production get back fed into the grid?
3) Does an ATS require a it's own subpanel of circuits to feed?
3a) If so, does that mean the solar can only be used to supply power on that subpanel?

In the end, what I'm wanting to figure out if there is a way to use the available solar on any arbitrary circuit in the home without having a full 200 amps worth of ATS.

 

[Supervstech]

Automatic transfer switch chooses energy source by a predetermined set of rules…
Ats cannot give some power from one place and some from another… it’s on or off.
Many have relays that turn off large devices when switched over to prevent overload of the backup power source.
Some are only on some circuits, some switch the entire energy source.

Now… there ARE inverters that can be configured to send some energy from solar to loads, and when demand exceeds supply, supplement with grid power…
Some can be configured to send back to the grid excess production… but that isn’t an ATS… it’s a grid tied inverter, or hybrid inverter setup.