Wiring to New Shop

[thecj3man]

My new shop is almost complete so I have turned my attention to getting ready to wire it up.

Last spring, I ran 200 amp service to my barn. The service comes underground from the POCOs transformer to my barn. They asked me to install 4/0-4/0-2/0 USE-2 cable to the new meter that is hooked to the side of the barn. Attached to the meter is a 200 amp box with a couple spots for breakers and a large set of lugs at the bottom. I put one breaker in this box to feed a panel in the barn for a few lights. I plan to utilize the large lugs to continue power to the shop.

Now that I am ready to continue on to the shop I have a question about which wire is appropriate. The local inspector that inspected the barn told me that when it was time to continue on the future garage to utilize 4 wire cable, but he didnt specify which one. The local electrical supply store has 4/0-4/0-2/0-4 and 4/0-4/0-4/0-2/0 USE-2 cable.

In my mind I think the same think that feeds the barn should be good enough for the shop, but I wasnt sure. Do I need the bigger neutral and ground?

Thanks,
WAP

 

[Aceman]

The wire you're looking for is mobile home feeder and you want the cable with the reduced neutral.

https://www.platt.com/platt-electri...le/4A22A14MOBILHMFDR/product.aspx?zpid=280732

 

[Charles (in GA)]

Keep in mind that the wire manufacturers call it MHF (mobile home feeder) but it is not marked as such, it is marked USE-2/RHH/RHW. This mult marking allows it to be run underground (USE-2) and inside of buildings (RHH/RHW). Without all of these markings/certifications, its use becomes limited.

After the disconnect at the meter, you need four wires, not three like used before the meter.

 

[thecj3man]

Keep in mind that the wire manufacturers call it MHF (mobile home feeder) but it is not marked as such, it is marked USE-2/RHH/RHW. This mult marking allows it to be run underground (USE-2) and inside of buildings (RHH/RHW). Without all of these markings/certifications, its use becomes limited.

After the disconnect at the meter, you need four wires, not three like used before the meter.

Both wiring options that I have available is marked as USE-2/RHH/RHW. Is there any advantage to the larger neutral and ground in the 4/0-4/0-4/0-2/0 wiring?

 

[alfredeneuman]

Using 4/0 Aluminum is good for 200 amps only, per 310.15(B)(7):
>For individual dwelling units of one family,two-family, and multifamily dwellings.
>For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit.
(In a nutshell, it's supposed to carry the total load to the dwelling)

I don't think that you qualify on either count.

You'd need to use at least 250KCM wire with a full size neutral, and a #6 Copper or a #4 Aluminum ground.

The POCO doesn't use the ampacity tables in the NEC. They are exempt, because the have their own engineers. They regularly specify smaller conductors than provided for in the NEC

 

[Aceman]

Using 4/0 Aluminum is good for 200 amps only, per 310.15(B)(7):
>For individual dwelling units of one family,two-family, and multifamily dwellings.
>For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit.
(In a nutshell, it's supposed to carry the total load to the dwelling)

I don't think that you qualify on either count.

You'd need to use at least 250KCM wire with a full size neutral, and a #6 Copper or a #4 Aluminum ground.

The POCO doesn't use the ampacity tables in the NEC. They are exempt, because the have their own engineers. They regularly specify smaller conductors than provided for in the NEC

You're right, 4/0 is considered 200 amp wire for dwelling units only. But, it is rated for 180 amps and 240.4(B) allows this to be used on a 200 amp breaker as long as the load doesn't exceed 180 amps. That's hard to do in a residential shop.

Using 4/0 AL on 200 amp breakers for a feeder is pretty much standard practice over here. But, if he wants the FULL 200 amp capacity, I agree, he needs to step up to the next size wire.

 

[whitedogone]

Using 4/0 Aluminum is good for 200 amps only, per 310.15(B)(7):
>For individual dwelling units of one family,two-family, and multifamily dwellings.
>For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit.
(In a nutshell, it's supposed to carry the total load to the dwelling)

I don't think that you qualify on either count.

You'd need to use at least 250KCM wire with a full size neutral, and a #6 Copper or a #4 Aluminum ground.

The POCO doesn't use the ampacity tables in the NEC. They are exempt, because the have their own engineers. They regularly specify smaller conductors than provided for in the NEC

Not correct. take a look at 240.4 (b) and table 310.16. You have to use full size Neutral as stated above. Usless you want to calc the load. You can't use the exception in 310.15(b(6.

 

[alfredeneuman]

It's not the first time I've been wrong and I doubt it will be that last, but you are right, whitedgone.

 

[thecj3man]

Thank you for the replys. I doubt that will ever come close to using 200 amps of service at any one time, but 200 amp service is what the POCO recommended installing.

So, let me make sure I understand. I can use either wire I listed above, but if I want true 200 amp capacity I need to utilize the 4/0-4/0-4/0-2/0 aluminum wiring?

WAP