Residential class 320 service

[bordrshane]

Good day,
I will be Installing a single phase class 320 service for a customer of mine. 400amp Cooper Bline meter main with a 300 amp main breaker. The service will be located on a CMU wall about 150 feet from house. At the house I will be installing a 400 amp distribution panel, that will feed 2x 200 amp sub panels. My calculated load is 220 amps, hence class 320 service. He also plans on adding a 5 hp motor and 20 hp motor at a later time for for his small home machine shop equipment. My question is
1. Is it better or easier to run a set of 500mcm al in 4 inch conduit, rather than 2 parallel smaller feeds in separate conduit? I am trying to save $$ on wire, but if much better I will use cu. Trying to keep my voltage drop under 5%. Where I am at, voltage is usually about 122-124 to 244-248v. The underground section has 2x 90's and a large sweep that would equate to 90 degrees sweep.. I was a lineman many years ago so pulling wire shouldn't be that difficult.

Customer is a good friend of mine. I am just trying to be that good friend and Keep the cost down, but still give him a quality and smart installation.

We also have a 10kw pv system that will be tying into the line side of the meter main.

Your thoughts on the wire size/installation from the meter main to the 400 amp panel at the house are greatly appreciated.

Thank you.

 

[electrofelon]

Good day,
I will be Installing a single phase class 320 service for a customer of mine. 400amp Cooper Bline meter main with a 300 amp main breaker. The service will be located on a CMU wall about 150 feet from house. At the house I will be installing a 400 amp distribution panel, that will feed 2x 200 amp sub panels. My calculated load is 220 amps, hence class 320 service. He also plans on adding a 5 hp motor and 20 hp motor at a later time for for his small home machine shop equipment. My question is
1. Is it better or easier to run a set of 500mcm al in 4 inch conduit, rather than 2 parallel smaller feeds in separate conduit? I am trying to save $$ on wire, but if much better I will use cu. Trying to keep my voltage drop under 5%. Where I am at, voltage is usually about 122-124 to 244-248v. The underground section has 2x 90's and a large sweep that would equate to 90 degrees sweep.. I was a lineman many years ago so pulling wire shouldn't be that difficult.

Customer is a good friend of mine. I am just trying to be that good friend and Keep the cost down, but still give him a quality and smart installation.

We also have a 10kw pv system that will be tying into the line side of the meter main.

Your thoughts on the wire size/installation from the meter main to the 400 amp panel at the house are greatly appreciated.

Thank you.

I will offer some comments. First, and I know this wasnt your question, but I find the design to not be very efficient. Typically, using a 320 socket with two sets of service conductors to two main breaker panels is by far the most cost effective way to do these. You have lots of 400 amp equipment there. Perhaps you have local rules and extenuating circumstances that make this is the way to go. One other thing is the PV system. Clearly you want to be set up for that. I Am not sure what exactly you mean by "tying into the line side of the meter main " For a line side connection you would want to be between the meter and the main, which can be difficult on a meter/main.

As far as wire size, first, do you intend to use the 83% allowance for dwelling unit services and feeders? See 310.15(B)(7). If so, you only need one run of 350 Al. I would probably do the one run of 350 in 3" - not worth parallel conductor here IMO . Do you have a main breaker in that distribution panel?

 

[ptonsparky]

20 hp single phase is a large load and will take a lot to get it started. My SEWAG about 80 amps run. Don't skimp on the feeder to his shop. Lights will dim when this thing starts up.

 

[electrofelon]

I recently hooked up a phase converter to supply a three phase 30 HP motor off a 200A loadcenter. Yikes. It seems to work fine, although I'm not saying the light dont dim!

 

[tom baker]

You can't use the 83% rule for loads not associated with the dwelling unit.
Not counting voltage drop:
Dwelling unit would be 4/0 AL
Shop would be 250 KCML
I would have one panel for the dwelling unit, and another for the shop, each 200 A

 

[lielec11]

....As far as wire size, first, do you intend to use the 83% allowance for dwelling unit services and feeders? See 310.15(B)(7)...l?

I'm piggy-backing on this thread because I've never had a project where I've applied this section before. After reading the commentary in the Handbook I have a question.

2014 Handbook commentary states, "The main service or feeder to a dwelling unit is permitted to be sized at 83 percent of the disconnect rating. The calculation is not based on the rating of the overcurrent device protecting the main feeder."

If it is not based on the rating of the OCPD protecting the main feeder, than what is it based on? Is that contradictory or am I missing something?

 

[electrofelon]

I'm piggy-backing on this thread because I've never had a project where I've applied this section before. After reading the commentary in the Handbook I have a question.

2014 Handbook commentary states, "The main service or feeder to a dwelling unit is permitted to be sized at 83 percent of the disconnect rating. The calculation is not based on the rating of the overcurrent device protecting the main feeder."

If it is not based on the rating of the OCPD protecting the main feeder, than what is it based on? Is that contradictory or am I missing something?

I think that is poorly worded. Note that the actual code language reads, "service rating"