Neutral Wire Sizing - 480V Wye 3PH

[customfab4x4]

Greetings,

I'm normally working on single phase applications for our contract work but we have a install at our own facility.

Can someone confirm neutral wire sizing?

We are running 480V in Wye configuration using 3 Aluminum conductors sized at 1000 MCM each which runs from a service disconnect to a MLO panel in our main building.

I'm having trouble determining if the neutral needs to be sized the same as the conductor wires. Of course, there is an immense cost associated with it as we are running 400 feet underground. I've researched the topic quite a bit and seem to be getting different answers across the web.

 

[Tulsa Electrician]

Sounds like these are feeders.
It depends on your loads.
All three phase loads or combination of line to netural loads.
You have to size to carry the calculated load.

 

[don_resqcapt19]

Greetings,

I'm normally working on single phase applications for our contract work but we have a install at our own facility.

Can someone confirm neutral wire sizing?

We are running 480V in Wye configuration using 3 Aluminum conductors sized at 1000 MCM each which runs from a service disconnect to a MLO panel in our main building.

I'm having trouble determining if the neutral needs to be sized the same as the conductor wires. Of course, there is an immense cost associated with it as we are running 400 feet underground. I've researched the topic quite a bit and seem to be getting different answers across the web.

If this is on the load side of the service disconnect, you don't need a neutral unless you have line to neutral loads. If you do have line to neutral loads, the neutral will be the larger of what the neutral load requires or the size of the required EGC for the feeder circuit.
If the service disconnect is not in the same building, you will need a building disconnect per 225.31 and 225.32.

 

[ptonsparky]

Do you have a neutral load? What is its calculated load? You will need EGs to your MLO.
What is the size of your SD?

 

[Tulsa Electrician]

As mentioned above. Have a look at 215.2 (A) (2) if one is installed and reduced.
Edit:
So the EGC must be sized correctly in order to size the netural correctly for a reduced minimum size

 

[customfab4x4]

Do you have a neutral load? What is its calculated load? You will need EGs to your MLO.
What is the size of your SD?

So I'm unclear about that and need to educate myself to a higher level. Luckily, I'm still in the final design stages of this power upgrade. Basically, I'm running the 480V 400A service to a main panel at the building (400 ft away). From there, I'm feeding power to various equipment which includes:

1) 480V 50HP sawmill
2) 480V 50HP sawmill #2
3) 240V 20HP CNC (step down transformer 480V to 240V)
4) Various 240V 3PH (3-5HP equipment)
5) Various Lights, outlets 120/240V 1PH

If anyone is available and would be interested in reviewing my design and assisting, I am totally willing to pay a consulting fee for you time! Please message me directly. I have a diagram that needs revision that I have attached. Thanks, Devin.

 

[ptonsparky]

So I'm unclear about that and need to educate myself to a higher level. Luckily, I'm still in the final design stages of this power upgrade. Basically, I'm running the 480V 400A service to a main panel at the building (400 ft away). From there, I'm feeding power to various equipment which includes:

1) 480V 50HP sawmill
2) 480V 50HP sawmill #2
3) 240V 20HP CNC (step down transformer 480V to 240V)
4) Various 240V 3PH (3-5HP equipment)
5) Various Lights, outlets 120/240V 1PH

If anyone is available and would be interested in reviewing my design and assisting, I am totally willing to pay a consulting fee for you time! Please message me directly. I have a diagram that needs revision that I have attached. Thanks, Devin.

I do not see any 277 volt loads, but if this is the Service Entrance you need the neutral. If it is a feeder to a sub, you do not.

 

[Joethemechanic]

1) 480V 50HP sawmill
2) 480V 50HP sawmill #2
3) 240V 20HP CNC (step down transformer 480V to 240V)
4) Various 240V 3PH (3-5HP equipment)
5) Various Lights, outlets 120/240V 1PH

I'm not seeing anything here that requires a neutral. Are there any 277 volt loads?

 

[PD1972]

Based on the diagram provided, it doesn't seem like there are 480V process loads that require a neutral. There also don't appear to be 277V single phase loads like lights. I am assuming that all standard building loads like lights and receptacles are going to be fed from the 200A, 120/240V residential panel.

That "Main Panel Rack" can be your service entrance panel. Just spec. a 480Y/277V, 3-phase, 4W, 400A mains, 400A MCB, NEMA 3R panelboard with feed-through lugs. The incoming 3-phase line that passes through the meter to that main panel rack will be 4-wire (3L + N). The neutral to ground bonding jumper happens at that main panel rack. The 2nd Main Panel can be fed through the feed through lugs, be protected by the 400A MCB upstream, and be a 480V, 3-phase, 3-wire, 400A MCB panel without a neutral. The 400 ft feeder can be 3 phase conductors plus an equipment ground conductor (EGC).

I would advise against using 1000kcmil aluminum. This is only 400A and it's only 400 ft so use parallel sets with smaller conductors so that whoever ends up installing this doesn't hate you. I would also advise you get a consultant (probably). This isn't too complicated of a system so if you have an EC lined up for this work, they could probably also help out with the design.

 

[customfab4x4]

Based on the diagram provided, it doesn't seem like there are 480V process loads that require a neutral. There also don't appear to be 277V single phase loads like lights. I am assuming that all standard building loads like lights and receptacles are going to be fed from the 200A, 120/240V residential panel.

That "Main Panel Rack" can be your service entrance panel. Just spec. a 480Y/277V, 3-phase, 4W, 400A mains, 400A MCB, NEMA 3R panelboard with feed-through lugs. The incoming 3-phase line that passes through the meter to that main panel rack will be 4-wire (3L + N). The neutral to ground bonding jumper happens at that main panel rack. The 2nd Main Panel can be fed through the feed through lugs, be protected by the 400A MCB upstream, and be a 480V, 3-phase, 3-wire, 400A MCB panel without a neutral. The 400 ft feeder can be 3 phase conductors plus an equipment ground conductor (EGC).

I would advise against using 1000kcmil aluminum. This is only 400A and it's only 400 ft so use parallel sets with smaller conductors so that whoever ends up installing this doesn't hate you. I would also advise you get a consultant (probably). This isn't too complicated of a system so if you have an EC lined up for this work, they could probably also help out with the design.

Yes, guys, correct. At this point, I have absolutely no immediate needs for 277V nor do I expect any for the future. All my power needs for equipment / drive motors:
1) 240V 1PH
2) 240V 3PH
3) 480V 3PH

Outside of that, 120V for lights and outlets for standard office equipment and power tools.

I am doing the install myself. My power company is hooking up power to the main service disconnect in 2 days. I'm responsible for everything else and am of course saving myself a small fortune by taking the responsibility. Of course, this is for my personal business on my personal property. And I certainly understand the safety precautions when working with conductors.

If anyone would have interest in consulting with me on the final design, I could pay $100/hr for a few hours worth of effort? Certainly, help me feel 100% confident about the design and future proofing.

Thanks again.

 

[customfab4x4]

I was able to revise my original 480V design as my power company gave me approval to use a 400A main service disconnect at the pole. Everything branches from my main building 400 feet away (not the pole).

And guys, I COMPLETELY understand the advice to hire an electrician to do this. I get it 100% and would give the same advice. Entire reason why I'd love to pay someone to consult on the schematic design to double check and advise. But ultimately hiring an electrician is out of the question and not something I have ever done, nor will ever do. I want to become knowledge in 3PH as we have plans to build at least 2 more buildings and bring in more power over the next few years.

One such example....I always wanted to build a pool. I have no experience. We complete our pool in 2 weeks. I did everything other than shooting the final quartz plaster. Beautiful $150K pool that I was able to complete for under $35K. Little complicated wiring. But I would aruge this project was far more complicated than a 3PH install. No offense extended!

Before that? Our 17 year old AC & Furnace went out. Did I hear a AC company? Nope. Installed a new system myself after about 3 months of research.

Before that? My wife had a LT4 camaro with an automatic. I hate automatics but like projects. Installed a Corvette T56 6-speed including all the fabrication for mounts and all the software programming required for it to communicate with the ECU properly.

Before that? I don't want to bore you!! You get the picture.

Just hoping someone wants to help a mid-40s engineer that has had a lot of success developing and building innovative technologies in the biotech space. Technical problems are food for life!

Just someone wanting to become much more knowledge in 3-phase so I can take all the jobs away from the licensed guys! YES, JOKING!!!