I have recently added on a room to my house. I have a main power supply out side with a two pole 100 amp breaker the neutral and ground are on same bus, the ground continues down tocopper pole in ground. Upstream ihave added alager box to accommodate more poles. The new box has the two hot wires coming into a 200 amp breaker and the neutral to its desidnated area. There are two ground busses one on each side of the poles connected together by a copper plate. My question, do I need to add a separate bus for the ground and place all the bare wires to that bus and the white or neutral to the two buses? There is not one now but looks like there is a place for one to be added. Also, what is a NTL tie strap and when do you bond it or not bond it? This is a siemans box.

Do you understand what you are doing? You do not add phase bus bars to a panel to increase its amperage. You can add additional ground and neutral busses providing your panel will accept them. You add them if there are not enough wholes available for ground or neutral conductors that are connected to your phase conductors that are mounted on the circuit breakers.

You are describing a two phase 100 amp main panel. You should have two hot phases and a neutral. Each phase is protected by a 100 amp breaker.

Since this is a main panel, Ground and Neutral are bonded at the main panel. Are you planning for the sub panel to be in the same building?

Upstream you are describing a 200 amp sub panel, however, by virtue of the Service Supply limitation the most that panel can have supplied to it is 100 amps. If you have an independent service drop or lateral connection to a 200 amp supply, which is extremley unlikely since you can only have one source of service entry, and therefore you would have to feed the subpanel from the main.

Exactly how are you doing that? Did you plan and install this subpanel by yourself? Has it been inspected by your LAHJ?

Did you call an electrician to do this work for you? If not, I strongly suggest you get a licensed electrician review the installation with you.

The NTS is basically described here:

http://www2.sea.siemens.com/NR/rdonl...CU_4094705.pdf

Ground needs to be run to the sub-panel and neutrals and grounds must remain separate in the panel. The removal of the NTS is that separation. Note that using main panels as sub-panels requires extra parts and removal of the Neutral Ground Strap.
Usually you also have to purchase ground lug kit as well.