i would use 2 ought if its for your home. go larger for commercial apps.
According to NEC, it's max rating in free air is 18 amps.
Sizing of ground conductors is based on the load capacity in amps of the generator. There is a table in the electrical code book which states an amperage and what size ground wire that is needed for that amperage.
[From NEC 2012 310.15(B)(16)] For a 350 MCM copper wire with: an insulation factor of 75 and 90 degrees C; not more than 3 current-carrying conductors in Raceway, Cable, or Earth; and based upon ambient temperature of 30°C ; has an amperage rating of 310 and 350 amps respectively.As a rule of thumb, you could consider their rating to be double with two sets paralleled together for 620 or 700 respectively. Be sure to account for temperature derating [NEC 2012 310.15(B)(2)(a)].See related links below for calculator.
A #8 copper conductor with an insulation factor of 60 degrees C is rated at 40 amps. For a built in safety factor, a #8 conductor with an insulation factor of 75 or 90 degrees C has a rating of 45 amps.
NEC Section 310.4 requires a 1/0 AWG and larger be used in parallel.
The NEC has a table that shows what size cable to use with each amperage and where it can be used.
It is 350 mcm cable and Table 310-16 1996 NEC gives limiting values of 260 amps at 60 degrees C up to 350 amps for 90 degrees for copper, or 210/280 amps for aluminium.
See NEC Article 392. It depends on the voltage, conductor size and the type of cable tray selected.
8000 watts divided by 240 volts equals 33.3 amps. If using NM cable indoors, Table 310.16 of the NEC says #8 wire is good to 40 amps. However, since this is a heating application which would qualify under "continuous duty" classifications(3hours or more of run time), then you figure it as 125%. This would in turn bump you up a wire size to #6. 33 amps times 125% equals 41.6 amps. Voltage drop would not be an issue even with #8 copper.
NEC 310.16 conductor ampacities NEC 240.4(D) For residential installations the smallest wire to be used is 14 AWG (15 amps rating) and for commercial installations the smallest wire to be used is 12 AWG (20 amp rating)
The formula for amps when kilowatts are stated is; kW x 1000/1.73 x Volts x pf. 10 x 1000/1.73 x 415 x .8 = 10000/574 = 17 amps. The electrical code states that motor feeders have to be rated at 125% of the motors FLA (full load amps). 17 x 125% = 21 amps. A #10 copper conductor with an insulation factor of 75 or 90 degrees C are both rated at 30 amps.
Couple of things wrong here. 30 isn't a wire size. If you mean a wire that can carry 30 amps that would be # 10. Now it depends on how many # 10 wires you want to put into a conduit that governs the size of the conduit.
It depends more on the insulation type not the voltage A very common wire type is THHN According to NEC (electrical standard popular in the USA) this type wire in size #12 is rated for 30 amps, but there is a footnote that states it can only be used for 20 amps maximum
According to NEC, it's max rating in free air is 18 amps.
Sizing of ground conductors is based on the load capacity in amps of the generator. There is a table in the electrical code book which states an amperage and what size ground wire that is needed for that amperage.
The CEC and NEC both cover this in the electrical code of the particular country.
475 amps, per NEC 310-16. Note that this is a maximum; there are many reasons to derate the current carrying capacity of the wire.