Subpanel Plan Check

[#crnxr]

Hey all. Long-time lurker and first post. Wanted to start by saying thank you to all the knowledgeable and helpful people here who are willing to lend advice to amateurs like myself.

Our home is a SFR with 200A service in WA state. I'd like to run 90A to a sub-panel in shed which is 200' from the main panel. For now I'll be running a few outlets for power tools, outdoor lights, and maybe a wall heater. I know 90A is overkill now, but I plan to utilize the full capacity at a future date when a larger shop is built.

Here's the plan...would appreciate feedback on anything I overlooked

90A breaker in main panel
1/0-1/0-1/0-#4 AL USE-2/RHH/RHW-2 (MHF) in 2" Schedule 80 conduit (18" deep) to shed
At shed...24 space QO panel with 100A breaker
(2) 5/8 dia. x 8' grounding rods spaced 6' apart with #8 bare copper
Neutral and ground not bonded at sub-panel

Questions...
1) I'd like to run the circuit through the back of the main panel using an LB fitting (See pic). Any issues with drilling the current knockout (Lower center on back of panel) larger to accommodate 2" pvc male adapter/lock ring and bushing?

2) Down the road I'd like to move this panel into a new detached shop, which will require about 40' more wire. Can I make a couple of extra trenches and lay more wire than I need now so that it can be extended later? With up to 240' I figured the voltage drop at just under 4%.

3) For outdoor lighting I planned to run some 12/2 UF-B from the shed about 40' to a quad outlet box. Can I run this in the same trench as the branch circuit?

Thanks very much in advance.

Kyle

 

[Moto]

If you have a basement or crawlspace, consider running the circuit in there as far as possible to minimize digging.

 

[75gmck25]

I ran SER through my unfinished basement from the main panel to the back wall of my house. I then put a junction box inside the house and transitioned to MHF and came through the wall with conduit. The conduit was buried from there to the garage. In your case it looks like you have a good open path for trenching, so maybe its just as simple to trench it and make the entire run outside.

As far as trenching in extra wire for future use, you may want to run 2" conduit instead of wire. Conduit is much cheaper for now, and 2" conduit gives space to run just about any size wire you might need in the future.

You can run other wire in the same trench if it still meets the depth and protection requirement. For example conduit is buried at 18", but direct bury wire must usually be at 24". You may also want to install a 2nd conduit for low voltage wiring (cable, cat 6, etc.).

There is a rule for a single 120, volt, 20 amp circuit, and I think it only needs to be buried at 12". I ran a 120 volt UF line from my garage about halfway back to the house in the same trench, and then branched off another trench from there to put a weatherproof receptacle next to my patio. For that circuit I installed a GFCI receptacle inside the garage, and then came through the wall and down into the trench. That allows me to reset the GFCI from inside the garage.

Bruce

 

[pattenp]

I'm not aware of MHF coming in 1/0-1/0-1/0-4. You can buy individual pieces of USE-2/RHH/RHW-2 in those sizes. If you are planning to use conduit you don't need direct bury rated wire so use XHHW-2. For the 200' distance the 1/0 Al will be good to maximize the 90A feed due to voltage drop. Be sure not to use URD(Use-2 only) cable inside because it's not allowed, RHH/RHW-2 and XHHW rated wire are allowed for inside use. Sch80 conduit is only required where above ground and is subject to damage. You can use Sch40 for underground. Keep VD at 3% or less if possible for a main feed.