Min Wire Size at 2000A service end box

[Zyb]

Hi,

We are going to do a line side tap at the service end box, the tap will be done by our general contractor so I will just need to specify the wire size?


Can anyone explain to me how to get the minimum wire size for 2000A Service End Box? I know per NEC250.122 the EGC will be 250MCM (correct me if i'm wrong) but how about the live wire? Thank you



Service End Box.jpg

[Mike 134]

I'm guessing since you asked your general contractor is a jack of all trades master of none. He doesn't have an electrical contractor that understands the tap rules?

I wish you good luck since not many DIYers have a 2000amp service.

[Zyb]

I'm guessing since you asked your general contractor is a jack of all trades master of none. He doesn't have an electrical contractor that understands the tap rules?

I wish you good luck since not many DIYers have a 2000amp service.

This is a commercial system, the general contractor have electrical contractor we just coordinate directly to the GC. do you know where can I find in the NEC for the minimum wire size?

[SunEagle]

This is a commercial system, the general contractor have electrical contractor we just coordinate directly to the GC. do you know where can I find in the NEC for the minimum wire size?

You really should have an Electrical Engineer that understands the latest NEC requirements for that project. There is more to know then just what size wire the NEC requires because the NEC is changed every 3 years and some places have not adopted the latest version.

So a DIY understanding for that project is not enough

Oh and a 500MCM copper cable is rated about 400amps so do the math when it comes to 2000amp connection.

Also a 2000amp system is usually 3 phase so you will need 3 times the cable plus a Ground wire and more then likely a Neutral wiring system. Good luck

[Mike 134]

Just a follow-up question. Looking at the size of your wires going to your disconnect your solar array in the 45-50 KW size?

[Zyb]

You really should have an Electrical Engineer that understands the latest NEC requirements for that project. There is more to know then just what size wire the NEC requires because the NEC is changed every 3 years and some places have not adopted the latest version.

So a DIY understanding for that project is not enough

Oh and a 500MCM copper cable is rated about 400amps so do the math when it comes to 2000amp connection.

Also a 2000amp system is usually 3 phase so you will need 3 times the cable plus a Ground wire and more then likely a Neutral wiring system. Good luck

Thank you for your reply. This is not a DIY, the building will still be constructed next year. the electrical contractor will order the service end box, I believe it will have a lug where they will do the line side tap.

[Zyb]

Just a follow-up question. Looking at the size of your wires going to your disconnect your solar array in the 45-50 KW size?

Yes, it has limited roof space, it is a small pv system connected to a NEW 2000A service end box.

[J.P.M.]

Yes, it has limited roof space, it is a small pv system connected to a NEW 2000A service end box.

That's about the biggest "small" system I know of.

[SunEagle]

Yes, it has limited roof space, it is a small pv system connected to a NEW 2000A service end box.

First off a 45-50kw system is not small. And second even with using the 1/3 amp rule for the tap you will be needing more then one lug to connect to. I hope your Electrical contractor understands what is needed to be safe for this installation.

[Zyb]

That's about the biggest "small" system I know of.

This is a commercial system

[Mike 134]

I'm just stunned your Electrical engineer doesn't know the answer.

Want me to take a guess?

[Zyb]

I'm just stunned your Electrical engineer doesn't know the answer.

Want me to take a guess?

I posted here to look for an answer, just disregard the post if you have no idea. Our design will be submitted to the General Contractor and will be check by their Electrical Contractor, to expedite the process I just want to submit the correct wire size.

[Mike 134]

I posted here to look for an answer, just disregard the post if you have no idea. Our design will be submitted to the General Contractor and will be check by their Electrical Contractor, to expedite the process I just want to submit the correct wire size.

Just an FYI as a retired master electrician I found your initial post puzzling because the drawing was done by someone who is familiar with electrical one-line drawings yet you're on the internet looking for answers rather than getting it from them. Just doesn't add up.

BTW Mutiple correct answers for the tap size governed by distance. Any licensed electrical contractor should know which Article to look for the answer before submitting for permits.

[SunEagle]

I posted here to look for an answer, just disregard the post if you have no idea. Our design will be submitted to the General Contractor and will be check by their Electrical Contractor, to expedite the process I just want to submit the correct wire size.

The size wire will still be determined by the local electric codes and the AHJ who will either approve or disapprove the installation. Asking for specific code requirements in an open forum is not going to get you the correct answer.

Sorry you feel your time was wasted. We just want your project to get approved and moved forward.

[Calsun]

The NEC code changes are always playing catchup and not to be relied upon 100% which is why I like to go to the equipment manufacturer's technical people. Solar is evolving and it does not fit neatly as of yet in the building local codes which relate primarily to fire safety. I view the codes as the minimum and not the optimum in many situations.

Important to check the max cable size that the connectors can accept and whether a smaller diameter jumper wire is allowed. The move to microinverters is driven in part by how much smaller the wiring can be than for DC runs from panels. Of course the solar farms have their panels on the ground so replacing a failed microinverter is far simpler than for a house with the panels mounted on the roof.