It is indeed a "all or nothing" type transfer switch, essentially an "A/B" electromagnetic selector switch. The transfer switches you are describing are for lower power generators where you have to be very choosey about what you are powering during an outage.

Obviously, the more power you have at hand, the less you have to worry about an overload.

For the incoming power feed, I have a "master" breaker box combined with the meter at the service entrance. This master box feeds all the high power circuits - the garage, the whole house panel, the dryer and the stove/oven.

I simply intercepted the 100A feed going to the whole house panel and ran it through the transfer switch. Since it's downstream of a 100A breaker, I just shut the power off while I did the wiring.

Now, if you have an integrated meter socket/breaker box with all the house circuits in one unit, you will have to install a 50 or 100A breaker in it and add a smaller box nearby to contain the critical circuits you wish to back up - the fridge, lights, well pump if needed, HVAC, etc...

Then, you can run that 50 or 100A feed circuit through the transfer switch.

On the other hand, if you have a simple meter socket which has an unprotected output that runs to your house breaker box, you will have to coordinate with your utility so they can remove the meter temporarily for you to do the work without having to work with energized wires.

If you can describe your setup or maybe snap a pic, I can take a look and offer a suggestion.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250