Technical Consultant

as you have just made your first post here on CR4, and I'm sure you found it by googling.... the answers to your questions can also be found the same way.

What is VERY apparent in your question, that you do not have the level of technical knowledge required to carry it through, so in your best interest and that of others you might work with.. i suggest you get an expert in to sort out whatever problems you have, or you read the standards applicable to the country you live in

There is no difference between a emergency and standby Automatic Transfer Switch. If you need one rated at 1,200 amps, you install that size.

The difference between "Emergency" and "Stand By" capacity has more to do with how the engine and generator sections perform in a warm environment. A generator rated at 1,875 KVA might work well at 40C ambient temperature for hours on end without overheating if the cooling system is properly sized, has not been reduced by dirt or other fowling. The same system when started from "Cold" can handle about 2,000 KVA for a short duration, without overheating, yet as the devices warm up, their internal temperatures can exceed design limits if the generator continues to run at the 2,000 KVA load instead of the design load of 1,875 KVA.

At my work, we have a single large generator powering 6 ATS's that each power critical loads within our facility. This allows us to distribute the loads among several power panels, and not have one large 1,200 amp ATS, but to have a pair of 500 amp ATS along with some in the 100 - 150 amp range. These are located in separate buildings, with the generator power running two main panels rated at 600 and 800 amps.

The system at my work meets the then current 2000 NEC codes, however it might not meet the codes in other states, or current codes.

Sizing ground wires is typical of any system, not just emergency generators. If your main conductors are protected for 800 amps, then neutral and ground conductors are sized according to the charts used for sizing such systems.

Some local jurisdictions can place increased requirements, such as a requirement to place a ground rod 20' into the ground, bond this to the incoming water meter main line, and also to the structural steel of the building. Other areas do not make all of these requirements.

One city that is located along the Pacific Ocean requires that all ground rods be made of Stainless steel, as they have experienced copper ground rods dissolving in the salty and corrosive ground in that city.

So you always need to contact the local building department for their local requirements.