...and by 10-4..I do mean 2 black(1 could be red or have a red stripe), 1 white, and a bare/green ground wire. The nomenclature is actually 10-3 with a ground..the ground is bare for interior wiring and the ground is sheathed in green insulation for exterior or below slab installs. I would invest in the controller first..the custom ones being made are code compliant with US 220v..meaning they utilize the neutral for 110v uses e.g. oven lights, led read out for dryer etc. Since 10-3 ground is required for all new installs. This is why most custom controllers are designed with 10-3 grounded in mind and usually have a 110v receptacle "always on" for something other than your lights like a fan.
Also, if you do end up installing a sub-panel..make absolutely sure your guy does not bond the white neutral and the ground wire together in the sub-panel..they must have separate lugs and not be connected..sometimes there is a tab that can be removed in between the neutral buss and the ground buss..the ground and neutral can only be bonded together @ your main service panel.
check this clip and paste for a good explanation of 3wire and 4wire 220v:
3-Wire 220 Volt Wiring
Most of today’s common appliances and fixtures operate off 110 volt wiring and circuits. In these cases connections to this equipment is done through three wires. The black wire, or “hot” wire, carries the electrical current to the device, the green wire, or bare copper wire, acts as the ground and the white wire is neutral, which completes the circuit. In turn, this wire can be traced back to the electrical panel where is connected to a single pole breaker to complete the circuit. Residential homes use alternating current (AC) which means the polarity of the lone “hot” wire reverses several times a second.
220 volt wiring, on the other hand, contains no neutral white wire. Instead, the black wire still carries a current but there is an additional “hot” wire which is usually red or blue in color. A bare copper wire, or green wire, serves as the ground wire as in 110 volt wiring. The two “hot” wires complete the circuit because one is positively charged while the other is negatively charged. Each wire delivers electricity to the appliance by alternating polarities and doubling the current. Subsequently, this wiring must be connected to a two pole breaker at the circuit panel to account for the two leads. In essence, a two pole breaker is 2 single pole breakers that have been wired together. This type of 220 volt wiring is most commonly used for providing power to electric water heaters, boilers, or condensing units.
4-Wire 220 Volt Wiring
Another type of 220 volt wiring is used to power appliances such as stoves and dryers. These devices require 220 volts to power their main function but use 110 volts to power accessory equipment such as clocks and timers. In addition to the two “hot” wires, this type also contains a white neutral wire to complete the circuit for the accessories that require a 110 volt circuit. As with any type of electrical wiring, a bare copper wire or green wire is also used as the ground wire. As with 3-wire 220 volt wiring, the use of 4-wire 220 volt wiring will require the installation of a two pole breaker in the circuit panel. Changes to the National Electrical Code (NEC) now require that this type of wiring be used predominantly in residential home construction. That is why most of today’s dryers and oven ranges come equipped with a 4-prong plug.