At least 000 AWG copper or better yet, 0000 AWG copper. Another consideration is how far the 200 Amps are to be carried. Wire has resistance and 0000 copper has a resistance of .04901 Ohms per thousand feet. At 200 Amps, this means that over one thousand feet the voltage will be 9.8 Volts lower than at the starting point.
Service wire required is AWG # 3/0 copper.
Yes, they are the same size wire.
A 200 amp service panel will require a # 4 bare copper ground wire.
A #1 copper wire with an insulation rating of 90 degrees C is rated at 140 amps.
Number 2 American Wire Gauge
Yes, but at every reduction in wire size there has to be a breaker sized to the smaller wire size. The wire size for 100 amp panels is recommended at #3 copper conductor. From the 200 amp feeder panel you will require a 100 amp two pole breaker for each of the two 100 amp services. Keep in mind that if you run the 100 amp services close to maximum this will take away the capacity of the 200 amp service for other branch circuits coming off of it. Also keep in mind that if the panels are located, not in the same building as the 200 amp service that the 100 amp panels will be treated as separate services and will have to be constructed like a 100 amp service. This includes ground rods. Also the bonding screw will have to be removed that connects the neutral buss to the panel enclosure.
Yes, they are the same size wire.
A 200 amp service panel will require a # 4 bare copper ground wire.
10 guage
Yes, the wire size has to be increased. The existing 100 amp service will now probably have a #3 conductor with an insulation factor of 75 or 90 degrees C which is rated for 100 and 105 amps respectively. Increasing to a 150 amp service will use a #1/0 wire size. If you are thinking of an upgrade, skip the 150 amp service and go to a 200 amp panel. New homes are installing 200 amp 42 circuit panels. The extra cost is only reflected in the materials as the labour costs will be the same regardless whether a 150 amp or a 200 amp panel is installed. The wire size for a 200 amp panel is #3/0. With an insulation factor of 75 or 90 degrees C the rating is 200 or 210 amps respectively.
AWG 2/0 copper wire.
AWG # 3/0 copper.
No. Usually when you get to that size panels the grounds are stranded.
A #1 copper wire with an insulation rating of 90 degrees C is rated at 140 amps.
Number 2 American Wire Gauge
Yes, but at every reduction in wire size there has to be a breaker sized to the smaller wire size. The wire size for 100 amp panels is recommended at #3 copper conductor. From the 200 amp feeder panel you will require a 100 amp two pole breaker for each of the two 100 amp services. Keep in mind that if you run the 100 amp services close to maximum this will take away the capacity of the 200 amp service for other branch circuits coming off of it. Also keep in mind that if the panels are located, not in the same building as the 200 amp service that the 100 amp panels will be treated as separate services and will have to be constructed like a 100 amp service. This includes ground rods. Also the bonding screw will have to be removed that connects the neutral buss to the panel enclosure.
40 amp
NEC code requires #6 bare copper.