3/4 pvc conduit already occupied with 240V 20A

[Oceanwolf]

I know, I know I need to check with an electrician. I wanted to be armed with information before I talk to someone.

I have a solar system on top of my detached garage. The main panel is at the main house. Sunpower added a 100A sub panel next to the main panel and have 12 gauge cables running to the garage through a 3/4 Pvc conduit. The distance is about 10 feet

My options are;

- adding a wall charger next to the sub panel and use the full 48A, but figure out a way, how to close the garage door with the cable.
- use the conduit between the subpanel and the inverter to add a 14-50 in the garage. I wonder if I can run another set of 4 6gauge in addition to the 12gauge ones in the same conduit.

What are your thoughts?

Onur

Confirmed MX 70D - who knows when it will show up.

 

[Aljohn]

Have you considered pulling the 12 gauge out and running just 6 gauge. That may be an alternative to trying to pull 6 gauge 3 wire through the 3/4 conduit with the other 12 gauge inside.

 

[Oceanwolf]

That is another option that I can think about

 

[DMage]

4 6ga wires will max a 3/4 conduit fill rating. You'd have to pull the 12 out. Having just done this with 3 6ga and 1 8ga ground in 1" conduit I am glad I upsized.

 

[tezco]

You would probably exceed the 40% fill rule if you wanted to add the 6 gauges on top of the existing wiring, and enclosing more than three current carrying conductors requires that you reduce the allowed current to 80%, on top of the 80% you have to allow for continuous current situations.

 

[FlasherZ]

Not only will you have issues with conduit fill, but you will also have to derate. More than 3 current-carrying conductors in a single raceway will require you to derate to 80% (for 4). This means that 12 ga. is only good to 16A, 6 ga will be good to 60A (instead of 75A conductor, 65A @ 75 degC termination).

 

[Oceanwolf]

Thank you folks. It looks like I need to replace the 12 gauges with 6 gauge.
What do you think about keeping the wall charger outdoors next to the subpanel. It has 25 feet cable, it will definitely reach to the car. I need to figure out how to prevent the garage door damaging the cable.

 

[Oceanwolf]

I opened both the subpanel and the panel that goes to the inverter. It looks like I have 10 gauge hot and neutral wires and a 2 gauge ground. That was a big surprise to me. I don't think I will mess with the solar setup but I will just bite the bullet and get another conduit run to the garage. Maybe a 1 1/4".
Inverter Box:

Subpanel: