Can I add a circuit and Wall Charger to a Sub-panel that gets power from Main and Solar.

[Doug183]

Current Setup.
- I have a Sub panel in the garage, rated for 100amp.
- The Sub panel has two inputs in a sense.
- One from the House main. In the Main box, there is a di-pole 50 amp breaker and the wires run to the sub panel bus bars directly. From the main to the sub-panel, there is also a neutral and ground.
- Second input is from the the solar panels, di-pole 30 amp breakers.
- The sub panel also has two other breakers in there, two mini double 15amp breakers running some lights and outlets. (60amps of breakers)

Question/Issue. The sub panel has two spaces open to add a di-pole (220) circuit for my Tesla wall charger. I want to just add a dipole 50 amp Circuit breaker and run some conduit and 6awg wire and be done. Logically this should work, but I am not experienced enough to be clear if I am causing a potential problem. I mean... looking at the circuit breakers, I am already at 120amps (20%) over the rated box, but that is pull right? 60 amps is the Solar going into that sub panel, so don't count those circuit breakers... Anyway, hopefully someone who has full experience with this will reply.

Thanks
Doug

 

[wwhitney]

Since the subpanel has a 100A bus rating, and the two sources of supply add up to less than 100A (50A from the grid, 30A from solar), you are not limited by the solar rules as far as adding any load breakers.

You are, however, limited by a load calc, to reduce the chance of overloading the 50A feeder from the grid. Since the lights/receptacles have a non-zero load, that would mean not using a 50A EVSE circuit. If the calculated load on those is less than 10A, you could use a 40A EVSE circuit.

Cheers, Wayne

 

[Art84]

I think you incorrectly calculated your double-pole breaker 30A. It's not 30A + 30A. It's a total of 30A but 220V.
When you say that sub panel main breaker is 100A, it's a 100A with 220V so the max load that this pannel can handle is 100A x 220V = 22000 watts/hour or 22 kWh.
So what you have:
1. Solar is up to 6.5kWh
2. Light one is up to 3.6kWh
3. Light two is up to 3.6kWh
So if all that run at max power you ll pul 13kWh, so your sub panel still have 9kWh that can be used.

9000watts/220V = 40A two pole breaker can be easily installed.