This answer is taken from the CEC. Table 17 states minimum size of grounding conductors. For a service conductor drawing 400 amps a #3 copper grounding conductor is needed. Also see rules 10-206, 10-700 and 10-812 if you have access to the code book.
Use #10 copper.
# 10 bare copper.
#6 bare copper wire.
The ground wire should go from the dryer directly back to the distribution panel. An external ground wire is not required. The ground wire that is in the cord set that is connected to the frame of the dryer and the ground wire that is in the feeders coming from the distribution panel, that is connected to the ground terminal in the dryer receptacle, is all that is required to satisfy the code requirement.
#6 wire is needed. If placing the subpanel in a garage at a good distance, it is recommended to also install a seperate ground rod .
Use #10 copper.
# 10 bare copper.
The size of the ground wire for a circuit is typically based on the size of the circuit breaker protecting that circuit. For a 200 amp circuit breaker, the recommended ground wire size is 4/0 AWG (American Wire Gauge) copper wire. This wire size helps ensure that the ground wire can safely carry any fault currents that may occur in the electrical system.
#6 bare copper wire.
In a 200 amp service panel, the ground wire is typically a bare copper wire or green insulated wire. It is connected to the ground bar within the panel. Make sure to consult the manufacturer's instructions or a licensed electrician for guidance specific to your installation.
#8 would be fine if you ground each panel separately to the ground rod
The ground wire size is determined from the current carrying capacity of the motor feeders.
The ground wire should come from the ground rod and to the main electrical panel grounding terminal.
Ground bus in the panel.
For a 100 amp service panel, typically a #8 copper wire or a #6 aluminum wire is recommended for grounding purposes. It's important to follow local electrical codes and regulations when selecting the correct size of the ground wire. It's always a good idea to consult with a licensed electrician for specific guidance based on your individual circumstances.
The ground wire should go from the dryer directly back to the distribution panel. An external ground wire is not required. The ground wire that is in the cord set that is connected to the frame of the dryer and the ground wire that is in the feeders coming from the distribution panel, that is connected to the ground terminal in the dryer receptacle, is all that is required to satisfy the code requirement.
For a 200 amp service, you would typically use a 4/0 AWG copper wire for the grounding wire running between the meter box and the service panel. This size is suitable for carrying the necessary current and providing proper grounding protection for the electrical system.