I have a sub panel (125 Amp Main Lug Load Center) with this Siemens Q21525CT breaker (15/25/25/15 Amp). It's a quad/tandem breaker with two 25Amp breakers common trip. This 25amp common trip is for 2 duplex 220v receptacles (4 outlets) for 4 - 600 watts HID lights which equals 11 amp @ 220v and 2 duplex 5-15 (each one on a 15amp breaker) for 110v (1,000 watts or less for miscellaneous in one 15amp and 800 watts 5000 BTU A/C at the other one). I plan to feed this sub panel with a 30amps double pole breaker. My question is… if I’m only using 11 amps @ 220v that means I have 49 amps for use @ 110v or 19amps only?:confused:

Your post is confusing, so I'll try to explain it this way:

Suppose you have a 30A 240 Breaker
Power is constant, so you have available 30*240 Watts or
120*30A + 120 *30A which is 30A per 120 V leg.

When you have only a 240 V load connected, there is no neutral current.

If you have a 20A on one 120 V leg and 10 amp on the other 120 V leg and a 5 A 240 V load connected to this breaker you have:

20+5 on one 120 V leg
10A + 5 on the other 120 V leg

And (25-15) or 10A flowing in the neutral.

Your post is confusing, so I'll try to explain it this way:

Suppose you have a 30A 240 Breaker
Power is constant, so you have available 30*240 Watts or
120*30A + 120 *30A which is 30A per 120 V leg.

When you have only a 240 V load connected, there is no neutral current.

If you have a 20A on one 120 V leg and 10 amp on the other 120 V leg and a 5 A 240 V load connected to this breaker you have:

20+5 on one 120 V leg
10A + 5 on the other 120 V leg

and (25-15) or 10A flowing in the neutral.

I'm using 10/3 to feed this sub panel. Sorry for the confusion Sir. I read at the internet 30amp @ 220v = 60amp @ 110v. My question is if I'm using only 12 amp @ 220v for my lights it that’s means I can use 36 amp (18 x 2) because it’s for 110v or its only 18 amp left for 110v receptacles? Sorry Sir if this doesn't make sense at all

OK, I think I get it.

Fed from a 25 A breaker at 240 V

12 A at 240 V for HID lighting.

So you have 25-12 or 13 Amps available at 120 from both poles.

Thus you have potentially two circuits with 13 A available at 120 V.

Are we on the same page?

OK, I think I get it.

Fed from a 25 A breaker at 240 V

12 A at 240 V for HID lighting.

So you have 25-12 or 13 Amps available at 120 from both poles.

Thus you have potentially two circuits with 13 A available at 120 V.

Are we on the same page?


I want to feed my sub panel with a 30 amps double pole circuit with 10/3 from my main panel. My sub panel has a quad/tandem breaker with two 25Amp breakers common trip for 220v and two 15Amp for 110v. Here is the sequence 15/25/25/15. My lights they are going to use 12 amps from this 30a circuit. That means I can use 18 amps for 110v? Or 36amp because they are only using only 110v? I read at the diy forums that 30amp at 220v = 60amp at 110v

I want to feed my sub panel with a 30 amps double pole circuit with 10/3 from my main panel. My sub panel has a quad/tandem breaker with two 25Amp breakers common trip for 220v and two 15Amp for 110v. Here is the sequence 15/25/25/15. My lights they are going to use 12 amps from this 30a circuit. That means I can use 18 amps for 110v? or 36amp because they are only using only 110v?. I read at the diy forums that 30amp at 220v = 60amp at 110v

I found the answer: I have 5760 watts total, to play with safely, regardless of what voltage. 30a*0.8 = 24a*240 = 5760 watts for constant use