400/320amp service entrance wire size

[Palmetto]

First off....I am not an electrician.....but I can follow directions.

I want 400/320amp service on a property I own...…...ranch out in the country. I don't need that much now, but have plans to expand.

I have talked to TNMP (texas-new mexico), and they say for overhead 320a service, my pole needs to be 30' from their pole mounted transformer. But they wont give me straight answer on what size wire I need to provide (from the meter to weatherhead) for them to splice into.


So I have my new meter pole set, and I am ready to buy my meter can & wire.

Can anyone help me figure out what size? The TNMP guy says he thinks code is 500mcm for that size service entrance...….

THanks in advance!

[Tony Pic]

Yes 500mcm copper will do for a 400 amp service. You can go to 600mcm alumalloy, but I do not know the current wire prices to see if Alu is feasible compared to copper.

[stoic]

Ampacity chart

https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/

[Mike D]

Are they dropping 320 amps or 400 amps?

My service is 320 amps and I installed 500MCM copper. I forgot how much of a ***** that stuff is to wrassle! [emoji15]






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[Mike D]

Are they dropping 320 amps or 400 amps?

My service is 320 amps and I installed 500MCM copper. I forgot how much of a ***** that stuff is to wrassle! [emoji15]






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You could also run 2 sets of 2/0 for 320. FWIW the lugs in my meter base were set up to accept this wire configuration.

You could run 2 sets of 3/0 for 400 amps.




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[Palmetto]

Are they dropping 320 amps or 400 amps?

My service is 320 amps and I installed 500MCM copper. I forgot how much of a ***** that stuff is to wrassle! [emoji15]






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They call it 320. The meter can I am getting is a Milbank u1079-r.

But I've been reading on the internet, and from what I can tell it's actually 400 amp service, but 320 continuous. I don't know.. I'm probably wrong.......


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[Rubi513]

They call it 320. The meter can I am getting is a Milbank u1079-r.

But I've been reading on the internet, and from what I can tell it's actually 400 amp service, but 320 continuous. I don't know.. I'm probably wrong.......


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You are correct.
Code allows an 83% factor for dwellings.
On a 400/320 service, parallel 2/0 or 400 mcm copper will work.
You would have to upsize for aluminum.

[Palmetto]

You are correct.
Code allows an 83% factor for dwellings.
On a 400/320 service, parallel 2/0 or 400 mcm copper will work.
You would have to upsize for aluminum.

Parallel huh? I have plenty of 2/0.......
Does that mean I would leave 6 wires hanging out the weatherhead for them?
I should probably ask the power company if they will accept that.

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[Rubi513]

Parallel huh? I have plenty of 2/0.......
Does that mean I would leave 6 wires hanging out the weatherhead for them?
I should probably ask the power company if they will accept that.

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Edit.
3 wires hanging out of each parallel run.
All power companies have different standards, so yes I would ask.

[FLASH_OUTDOORS]

How are you planning on building the service?? 400a is a large service to mount on a pole. The only way you could do it without the meter being 8+ feet off the ground is to do the meter on one side of the pole and disconnect on the other. This will still force you to have a very expensive underground. I would build a rack with the service on it and run underground up their pole. That way you can put 2 200a disconnects on the service and run aluminum 4/0 Undergrounds with a #4 ground to save money. I believe that power company requires copper to there meter and out of it. Once you hit the gutter you can go to aluminum to save money.


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[Killer]

For Oncor they have a 320 amp meter and meter base. Most people come off this meterbase with two runs of 4/0 on the loadside going to two 200amp disconnects.
The meterbase has two lugs per phase on the loadside. You need to make sure it has double lugs on the line side too before you parallel runs out the weather head. We won’t let you double lug wire on one set of lugs. You probably would need two weather heads to parallel wire on the line side of the meter.
I assume this is the same type of meter base you are using.
TNMP should have a drawing showing what you can do on the service entrance. They most likely won’t tell you what wire size to run because of liability.

[Palmetto]

How are you planning on building the service?? 400a is a large service to mount on a pole. The only way you could do it without the meter being 8+ feet off the ground is to do the meter on one side of the pole and disconnect on the other. This will still force you to have a very expensive underground. I would build a rack with the service on it and run underground up their pole. That way you can put 2 200a disconnects on the service and run aluminum 4/0 Undergrounds with a #4 ground to save money. I believe that power company requires copper to there meter and out of it. Once you hit the gutter you can go to aluminum to save money.
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I built a nice switchrack using 8" treated poles spaced 5' apart. One is 16' tall, the other is 6'. I cut two treated 10' long 2x12's in half, and lag bolted them to the poles. should be plenty of room for everything. If I go underground to the pole its going to be more expensive. All I have to do is go about 9' up the pole to a weather head, and TNMP splices in and takes care of the rest.

For Oncor they have a 320 amp meter and meter base. Most people come off this meterbase with two runs of 4/0 on the loadside going to two 200amp disconnects.
The meterbase has two lugs per phase on the loadside. You need to make sure it has double lugs on the line side too before you parallel runs out the weather head. We won’t let you double lug wire on one set of lugs. You probably would need two weather heads to parallel wire on the line side of the meter.
I assume this is the same type of meter base you are using.
TNMP should have a drawing showing what you can do on the service entrance. They most likely won’t tell you what wire size to run because of liability.

They do, and I am following it. I just didn't know what size wire to use because their rep will not be clear about it. I did not know it was a liability thing. That makes sense why he is being so wishy washy.

I will definitely make sure to get the double lugs on the load side. Thanks for the reminder. I already have some 2/0 from a previous job, so I will use that to split off to my two 200a panels.

It looks to me like 400mcm copper is the size I need from the line side of the meter to the weatherhead.

[FLASH_OUTDOORS]

You are correct with 400


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[Palmetto]

You are correct with 400


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Thanks!

[Palmetto]

Does the neutral also have to be 400mcm?

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