Adding subpanel to a shed

Question

Thanks in advance for anyone providing insight for me. I apologize if answers for my situation can be found in another post that I've missed.

I have a shed outside my home that currently has no power. I'd like to run power to it and install a 60A subpanel to support a couple of circuits. Currently, I have 200A service coming to the house. The panel inside the home is about 50 feet away so there's a 200A service disconnect with room for 4 breakers at the meter. The shed is about 5 feet from the service entrance.

What I'm planning is to install a 60A breaker in the panel at the service entrance and run 6 AWG copper underground to the subpanel in the shed. I plan to use metal conduit because no one wants to be digging a couple of feet down. I'm comfortable with the requirements for the circuits inside the shed.

Pennsylvania uses the 2014 NFC. Do I have the correct wire for the circuit? Is my approach with the breaker in the service entrance valid? Lastly, do I need a separate grounding rod for the shed? It seems silly to add another grounding rod a couple of feet from an existing one.

Lastly, a (really) crude drawing of it all. Black is existing. Red is proposed.

Answer 1

You have the right general idea

The rigid conduit is fine -- you will only need to dig 9-12" down for this, and a 2" RMC or EMT provides plenty of space to make for an easy pull and future expansion. Furthermore, the metal conduit provides the equipment grounding conductor to the shed, which saves you a wire in the pull (two black hots and one white neutral is fine). Also, finding a 60A breaker for your meter-main isn't an issue -- a THQL2160 will do the job, and should be available anywhere circuit breakers are sold.

You still will need ground rods at the shed though

You will need two ground rods (minimum 8' long and 6' apart) at the shed, with a 6AWG copper wire from there to the shed subpanel ground bar, though. This provides a path to ground for lightning induced transients, while the metal conduit returns fault current back to the service entrance (aka its source). As a result of this splitting of return paths, you will also need to ensure that the bonding screw or strap has been removed (or was never fitted to begin with) to the subpanel, and will also need separate neutral and ground bars there.

Other notes

You should use an inch-pound torque wrench or torque screwdriver (depending on the torque setting called for) on all breaker and panel lugs to torque them to manufacturer specifications -- this improves system reliability vastly, and is also a new requirement in the 2017 NEC (110.14(D)).

Also, the shed subpanel will need to have a main breaker in it to serve as a disconnecting means for the shed. It is OK to use a big main breaker here, though, since the upstream 60A breaker in the service-entrance device will protect the feeder wires from overcurrent. As a result, the simplest way to go here is to get a 100A or 125A, 24- or 30-space, main breaker panel and fit it with ground bars if it doesn't already come with such. That way, you will have plenty of space for expansion -- if you want more current to the shed, you can swap the feeder breaker and wires for larger ones, and you can also add circuits fairly freely there without worrying about running out of breaker spaces.