You will need to use #8 wire.
8 AWG copper.
You need a 60 amp breaker.
40 amp
Look on the heater and see what amps it is pulling. That will determine the wire size and breaker size. It must be on a dedicated circuit. 15 amps = AWG # 14 wire with 15 amp breaker 20 amps = AWG # 12 wire with 20 amp breaker 30 amps = AWG # 10 wire with 30 amp breaker 40 amps = AWG # 8 wire with 40 amp breaker
If you use 250 or 300 MCM wire you will need a 2 1/2" weather head. If you use 300 MCM wire then you will need a 3" weather head.
You will need to use #8 wire.
8 AWG is typical.
2AWG.
8 AWG copper.
You need a 60 amp breaker.
A 200 amp service panel with a 60 amp sub-panel.
40 amp
2 or 4
You will need AWG #3 if it is a short run.
AWG 2/0 copper wire.
Look on the heater and see what amps it is pulling. That will determine the wire size and breaker size. It must be on a dedicated circuit. 15 amps = AWG # 14 wire with 15 amp breaker 20 amps = AWG # 12 wire with 20 amp breaker 30 amps = AWG # 10 wire with 30 amp breaker 40 amps = AWG # 8 wire with 40 amp breaker