New 30x40x12

[tpilgrim]

Just had a 30x40x12 built. it is about 25 ft away from the service meter. There is also a 200A main panel just under the meter on the pole. My plan is to run underground feed from the main panel on a 100Amp breaker underground in conduit to a sub panel inside the shop.

2 mini splits on separate 20 amp breakers and a run of led lights. Not too heavy but maybe a little fluxcore welder at times on the 20 amp and an air compressor.

I need help determining the correct wire to use.

I figure quadruplex and a couple of grounding rods.

Shop is 25 feet from main panel, so about 35-40 ft of wire from breaker to sub panel lugs underground in conduit is my thought.

Calling all professionals!

 

[sparky 1971]

2-2-2-4 or 2-2-4-6 MHF with a 90 amp breaker at the main feeding a 100 amp main breaker panel with an isolated neutral (buy your own ground bars and throw away the bonding screw) at the shop. If you insist on using a 100 amp breaker to feed it, you will have to use #1 Aluminum or #3 copper and while it's still easy, it's not quite as easy or cost effective as using the MHFC.

 

[tpilgrim]

2-2-2-4 or 2-2-4-6 MHF with a 90 amp breaker at the main feeding a 100 amp main breaker panel with an isolated neutral (buy your own ground bars and throw away the bonding screw) at the shop. If you insist on using a 100 amp breaker to feed it, you will have to use #1 Aluminum or #3 copper and while it's still easy, it's not quite as easy or cost effective as using the MHFC.

Thanks for the information. I'm not stuck on a 100 breaker for the feed. What would the recommendation be?

 

[meathooker]

2-2-2-4 or 2-2-4-6 MHF with a 90 amp breaker at the main feeding a 100 amp main breaker panel with an isolated neutral (buy your own ground bars and throw away the bonding screw) at the shop. If you insist on using a 100 amp breaker to feed it, you will have to use #1 Aluminum or #3 copper and while it's still easy, it's not quite as easy or cost effective as using the MHFC.

The south wire voltage drop calculator shows #1 copper or 1/0 aluminum.

are you getting you numbers out of the code book?

 

[sparky 1971]

The south wire voltage drop calculator shows #1 copper or 1/0 aluminum.

are you getting you numbers out of the code book.

Actually, I pulled them out of my head but I know it's in the code book. Table 310.16, use the 75° column if you want to double check. And voltage drop isn't going to be a concern.

 

[sparky 1971]

Thanks for the information. I'm not stuck on a 100 breaker for the feed. What would the recommendation be?

Recommendation for what be?

 

[meathooker]

Actually, I pulled them out of my head but I know it's in the code book. Table 310.16, use the 75° column if you want to double check. And voltage drop isn't going to be a concern

you sound like my buddy - he’s a walking code book!

 

[tpilgrim]

Recommendation for what be?

You mentioned if I insist on using 100 amp panel and breaker... Thought maybe there was a better option you knew of.

 

[sparky 1971]

You mentioned if I insist on using 100 amp panel and breaker... Thought maybe there was a better option you knew of.

The better option is the 90 amp feeder in my first post...

 

[tpilgrim]

@sparky 1971 I've gone the 2-2-4-6 MHC route you mentioned. Can you advise on the ground rod layout for this? Any help is appreciated!

 

[sparky 1971]

@sparky 1971 I've gone the 2-2-4-6 MHC route you mentioned. Can you advise on the ground rod layout for this? Any help is appreciated!

Two 5/8" X8' rods spaced at least 6' apart. Run a #6 bare solid conductor from the panel ground bar through the clamp on the first rod and on to a clamp on the second. You can also use two clamps on the first rod but that's a waste of $5. I also like to put the rods in the trench before backfill, it makes the job of getting them below grade a whole bunch easier.