An FS140 on the main panel will provide protection for the entire electrical system. However, having several layers of protection is always the best strategy. This would mean smaller SPD's at subpanels and point-of-use surge protectors at receptacles powering sensitive equipment such as computers, microwaves, garage door openers, entertainment centers, etc.
No, NEC says that you may not put more than one wire in a terminal.
A dedicated two pole, 20 amp breaker is what is specified in the literature that comes with this unit. It doesn't really make any difference because the cost of a 30 amp, two pole breaker is within pennies of a 20 amp two pole breaker so if you are more comfortable with a 30 amp breaker, go ahead and use one. I have installed several of these devices using the 20 amp breaker that is specified. The only thing that IS important is that the breaker is dedicated to this unit and not connected to anything else.
Do not try yourself you will probably die. Much more complicated then switching off a breaker.
I would connect to any convenient breaker pair. If unsure, just use a volt meter between the two breaker connections and make sure you get 240 volts on the pair selected before you turn off the main breaker to do your wiring.
Good question, I have not seen the subject picture, but you are making correct statements. Just remember that normal sized breakers next to each other are on opposite phases because of the way the panel buses are arranged! By the way, I do not believe this product is intended for 3phase panels.
Ideally, and in order to only install one unit, you should connect this surge protector to the main electrical panel that's on the exterior of your home. I have a similar situation in my home, where my main service panel is located outside my house but I don't have any space in the main panel, to install another breaker. What I did was install two of these units to my electrical sub panels, which cost me another $250 dollars but considering that the cost of replacing my AV equipment and the major kitchen appliances could be tens of thousands of dollars, I figured it would be worth the price of another surge protector unit. If you CAN connect this unit to your main electrical panel, you may have to install it inside a weatherproof/rain tight box and connect that box to your panel in order to protect it from the weather or from damage by inadvertent contact. You don't have to install the dedicated, two pole, 20 amp breaker to which this unit is connected at the top of your panel. The breaker can be installed anywhere inside the panel.
Yes, that is exactly how I mounted mine and it made the installation very fast and easy.
This unit can be used in any application that has a 120/240 volt, single phase, four wire system. You might want to contact Siemens before you purchase this device, to make sure it will be sufficient for your application needs but this device can't differentiate between a commercial or residential application as long as it is wired to the system described in my first sentence.
It depends on your current setup, i.e., physical space and available breaker space, flush mount or not, indoor or outdoor installation, etc. You should get a quote.