Yes, if you are running it no farther than 100 feet. If you are going over 100 feet use AWG # 10 wire on the 20 amp breaker.
Minimum size is 10 gauge with a 30 amp breaker. To be safe I would install an 8 gauge with a 40 amp breaker.
Look to see if the 30 amp panel is fed with a two wire or a three wire. If it is a two wire then you are out of luck. If the panel is fed with a three wire then the panel should have the neutral terminated in the panel. It is this neutral that you need for 120 volt connections. You didn't state how many panel slots there are in the panel. If you are able install a 15 amp breaker into the panel and connect the wires going to the load. The black wire will go to the breaker and the white wire will go to the neutral bar in the panel.
You need a 60 amp breaker.
A short, which will trip the main breaker.
15 amps
No, 10 gauge wire requires the use of a 30 amp breaker. A 20 amp breaker is only used on 12 gauge wire.
Minimum size is 10 gauge with a 30 amp breaker. To be safe I would install an 8 gauge with a 40 amp breaker.
Look to see if the 30 amp panel is fed with a two wire or a three wire. If it is a two wire then you are out of luck. If the panel is fed with a three wire then the panel should have the neutral terminated in the panel. It is this neutral that you need for 120 volt connections. You didn't state how many panel slots there are in the panel. If you are able install a 15 amp breaker into the panel and connect the wires going to the load. The black wire will go to the breaker and the white wire will go to the neutral bar in the panel.
You need a 60 amp breaker.
No. A 20 amp breaker needs 12 gauge wire.
no
The question isn't what you're powering with a particular gauge of wire, but what's the current draw. If the metal halide light can run on a 15 Amp breaker (from the breaker panel), fine use your metal halide in your residential application and run it on the 14 gauge wire.
A short, which will trip the main breaker.
A domestic D/W uses 14 gauge wire.
Copper SE cable gauge 00 from the meter socket to the breaker panel for a 200A service. Then 8, 10, 12, and 14 gauge wire depending on the load.
Use AWG # 6 wire.
Yes, if the existing wiring you are adding to is 14 gauge. If it is 12 guage then you must use 12 gauge. If you are running wire from the service panel it is fine as long as you install a 15 amp breaker.