# 600A 277/480 wye service



## SE Electric (Dec 26, 2017)

I'm about to do a 600A service install for a company and just wanted to run my game plan by some people with more experience than me. It's a pad mount transformer feeding in from the POCO. I'm trenching ~330 feet and running 3 parallel runs of 350 al xhhw for the ungrounded conductors, and 1/0 al xhhw for the neutral piped in 3" sched 40 pvc. Jumping up into 3 200A disconnects (600V 600A disconnects are effin expensive!) outside the building and running 2-1/2" EMT inside into a panel with a 600A main. 
Am I screwing up on any of my calcs for sizing?
Any thoughts on how to do it cheaper/easier?
Reasons not to downsize the neutral?
Should I find a new career?:vs_laugh:


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## matt1124 (Aug 23, 2011)

What happens if 2 of the 3 disconnects are off and there’s a heavy load?


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## MXer774 (Sep 1, 2014)

Do you not have a stamped set of drawings showing a one-line?

You are planning on routing from the pad mount into (3) 200A Discos for one metered service? Where is the metering device (pad mount or building)? How are you planning on landing your undergrounds into the discos, each disco gets a pipe from below grade :laughing:? Wireway below them?

Why would you care the expense of the disconnect? The customer pays for it and you get to mark up the costs, making money off it. You are actually going to cost the customer more in labor monkeying around with three separate enclosures instead of one. I wouldn't even think of this unless they were separate metered services. 

Here's my typical setup for this. For a 600A service using aluminum. (2) sets of 4 #500 in 4" Raceway. I wouldn't downsize neutral, it won't save that much. From pad mount to CT can (if metered on the building). CT can to 600V 600A 3Ø 4W N3R FUSED Disco. N3R Disco to MDP. MDP to branch panelboards.


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## SE Electric (Dec 26, 2017)

new career it is. 
What happens if 2 of the 3 disconnects are off and there’s a heavy load?
Thought about that but I didn't really see it as a problem if everything was labeled unless it was malicious
Do you not have a stamped set of drawings showing a one-line?
no this is an additional service being installed for expansion.
POCO and AHJ both approve 2 services on building
You are planning on routing from the pad mount into (3) 200A Discos for one metered service? Where is the metering device (pad mount or building)? How are you planning on landing your undergrounds into the discos, each disco gets a pipe from below grade ? Wireway below them?
Each disco would be piped into from below grade  CT's will be on the building
Why would you care the expense of the disconnect? The customer pays for it and you get to mark up the costs, making money off it. You are actually going to cost the customer more in labor monkeying around with three separate enclosures instead of one. I wouldn't even think of this unless they were separate metered services. 
touche, this is why I wanted to get ripped to shreds on here.:laughing:


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## Southeast Power (Jan 18, 2009)

SE Electric said:


> I'm about to do a 600A service install for a company and just wanted to run my game plan by some people with more experience than me. It's a pad mount transformer feeding in from the POCO. I'm trenching ~330 feet and running 3 parallel runs of 350 al xhhw for the ungrounded conductors, and 1/0 al xhhw for the neutral piped in 3" sched 40 pvc. Jumping up into 3 200A disconnects (600V 600A disconnects are effin expensive!) outside the building and running 2-1/2" EMT inside into a panel with a 600A main.
> Am I screwing up on any of my calcs for sizing?
> Any thoughts on how to do it cheaper/easier?
> Reasons not to downsize the neutral?
> Should I find a new career?:vs_laugh:


Good to hear from you Cletius. 
I cant see a single thing right with any of this.
You have a big problem on your hands.


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## SE Electric (Dec 26, 2017)

Thanks for the help d-bag(se power). Glad you were never green and asking for advise before you f'd something up. I only have old school guys around here to ask for advise. Trying to move on to bigger projects and wanting advise not some guy talking smack, at least add something to the conversation. Constructive criticism is one thing but now I just know who not to talk to on here.


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## SE Electric (Dec 26, 2017)

Awesome. I'm an idiot and just screwed up any chance of getting help on here. Original plan was to feed 3 200a panels. Didn't need that much space so changed to one 600a and had tunnel vision when I typed the original post.


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## matt1124 (Aug 23, 2011)

Lol!


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## micromind (Aug 11, 2007)

MXer774 said:


> Do you not have a stamped set of drawings showing a one-line?
> 
> You are planning on routing from the pad mount into (3) 200A Discos for one metered service? Where is the metering device (pad mount or building)? How are you planning on landing your undergrounds into the discos, each disco gets a pipe from below grade :laughing:? Wireway below them?
> 
> ...


And the MDP doesn't need a main.


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## SE Electric (Dec 26, 2017)

I get that it's bad form to have the disconnects set up like that, but it's not violating any NEC code, correct?
230.2 says it's ok if I went with the original plan of 3 200A panels, 
My understanding of 230.71(A) says even my original post would be alright.
Hell, 230.71(B) says you can use single pole switches for a disconnect as long as they're labeled or tied together. 
In what situations would it be viable to have your main disconnect for a single service broken up into multiple throws? Not planning on following that path now, just curious.
Call me a dip****, but at least tell me where I'm messing up, or what I need to read up on. 

Thanks guys,
Cletus 

(When you try to insult someone, you should at least spell it correctly. Cleitus was an Illyrian king of the Dardanian State attested in 335 BC-Wikipedia) :laughing:


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## Southeast Power (Jan 18, 2009)

SE Electric said:


> Thanks for the help d-bag(se power). Glad you were never green and asking for advise before you f'd something up. I only have old school guys around here to ask for advise. Trying to move on to bigger projects and wanting advise not some guy talking smack, at least add something to the conversation. Constructive criticism is one thing but now I just know who not to talk to on here.


Sorry Cletus,
I honestly thought you were messing with us.
This type and size service is my exact niche.
Ill be somewhat constructive.
I would not reduce the neutral on a WYE system. Your calculations might be good, you might not need it at all but, what happens when another business moves in and needs that neutral capacity. 
Second, I wouldn't run 3 conduits, 2 will be just fine and I would run 4" instead of 3" for that long of a run and pull 4x 500s or 4x600s if you have a voltage drop problem.
I have no idea what you are getting at with 3x200 amp disconnects feeding a 600 amp main breaker. Makes no sense. 
I would use a 600 amp fused disconnect or breaker outside and feed a MLO panelboard inside. Or if its close to an outside wall, just a 600 amp main in the panelboard and a shunt-trip outside if your AHJ requires an outside disconnecting means. 

Finally, you should have some professional engineering or someone credentialed to design and seal your plans. 
I design all of my own services and have an engineer look them over and seal them. Normally you would have an engineer design it but, sometimes they dont consider any site conditions and then you get screwed.


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## MXer774 (Sep 1, 2014)

I'm not sure if it would be a violation to use (3) separate 200A discos to feed (1) MDP, although a terrible design that I wouldn't want my name on. Too lazy to search for it. Maybe a code guru will answer that and provide a reference.

I know it wouldn't be a violation if you were to feed (3) separate 200A Panelboards. But then you fall into the metering issue. I ask again, how is this service to be metered? Pad mount meter or CT on building? You would also run into the issue of limited breaker frame sizes if any large loads are needed. 

Trust in my first post, that is how it should be installed. Or as SE described above.


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## MTW (Aug 28, 2013)

I don't get the 3 disconnect thing either. Here that service would be CT metered, either at a CT cabinet or right at the padmount itself. 

I would do as others have suggested - a 600 amp main outdoors or use a 600 amp main breaker in your MDP. Ask your supplier to put together a gear package and you will get better pricing.


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## matt1124 (Aug 23, 2011)

Im not as well versed in code as Steve but I’m pretty sure you can’t group disconnect parallel feeds of the same circuit. They all have to be off or all on for it to even not burn up, much less be inadvertently energized during service


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## SE Electric (Dec 26, 2017)

I'll be the first to admit I'm way out of my comfort zone. I've always done residential, just was eligible to take my unrestricted. I wouldn't take on any project w/o a thorough understanding of what I'm doing. The advise I got to begin with from a local guy was for a 400a service with 2 200a panels. I scaled that up into a 600a with 3 panels. Realized that wasn't a great plan and changed over to the single 600. I got too focused on everything else and didn't even think about having 3 discos feeding into a single panel. Just asking why NEC allows it in certain circumstances. Aparently I'm in way over my head and should stick to residential work. Genuine thank you again guys.


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## glen1971 (Oct 10, 2012)

Glad to see the OP is changing their plan.. The original design was a poor thought...


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## SE Electric (Dec 26, 2017)

So I f***ed up completely on the disco's. :wallbash:. But I'm stubborn and still have some questions, I really want to understand this. You guys know your s**t. :bangin:
Where am I messing up on this part? Even up to 600 Al I have no idea what the load would be (linear or non-linear), and like you said Southeast Power, there's no idea of what the requirements of a new company moving in would be. 310.15(B)(5)(c) says with a non-linear load on a 4-wire 3 phase wye system, the neutral becomes a CCC, 4 CCC's in the conduit means a adjustment factor of 80%-310.10(H)(4) and 
310.15(B)(3)(a). Even up to 600 AL that puts you at 340A derated to 272A. 500 AL puts you at 310A and 248A.
That's running @75 deg terminations/110.14(C)(b)(2). 
I think. :blink::laughing:
Sorry to make people break out a code book, this is all coming from 2014 btw.


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## micromind (Aug 11, 2007)

I think 2 - 200 amp fused disconnects each feeding a 200 amp panel (no main) and another fused disconnect feeding a 480 - 120/208Y transformer would be the least expensive way to go. 

If I didn't know the loads, I'd likely make the transformer disconnect 200 amp and use a 150 KVA transformer. Then I'd set 2 - 225 amp main breaker 120/208 panels. If the wire from the transformer to each 120/208 panel is less than 10' long, the main breakers would qualify for overcorrect protection.


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## SE Electric (Dec 26, 2017)

There's already a 120/208 service coming into the building. No need for additional panels.


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## LGLS (Nov 10, 2007)

SE Electric said:


> There's already a 120/208 service coming into the building. No need for additional panels.


That's a big no-can-do around here. 1 service on a structure.


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## MTW (Aug 28, 2013)

LawnGuyLandSparky said:


> That's a big no-can-do around here. 1 service on a structure.



The NEC specifically allows an additional service of a different characteristic.

230.2 (D)


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## SE Electric (Dec 26, 2017)

Approved by both poco and ahj.


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## varmit (Apr 19, 2009)

NO, you can not do a service as you describe in your original post.

1.) If you "paralleled" 3 disconnects, Any one disconnect could bypass the others. Also, the load lugs would be energized from the connections at the 600 amp panel - EVEN WITH THE DISCONNECT OFF unless all were off. A disconnect must disconnect all power in the circuit down stream of the disconnect.

2.) If the 3 disconnects were allowed to be installed, they would be the service disconnects, so they would be required to be fused. PARALLELING FUSES IS NOT ALLOWED. A fifth conductor ( grounding conductor) would be required from the disconnect(s) to the panel.

3.) The only permissible way to have separate disconnects in each set of the paralleled service conductors would be if each set of conductors supplied power to different panels (loads). 230.74

Correct installation options:

1. Install the 600 amp panel, with main on the wall close to the outside building wall. Connect the service conductors here and do all grounding and bonding.

2. If you will have no more than 6 breakers in the service panel, you would not need a 600 amp main breaker. the feeder breakers would serve as the service disconnects.

3. if the service panel can not be installed near the service entry point to the building, a 600 amp fused disconnect would need to be installed at the point of service entry into the building. all grounding and bonding would be done at this disconnect. 

4. You could install three separate 200 amp panels with each powered with one set of the 3 X paralleled service conductors. If these panels can not be installed at the point of service entry into the building, disconnects for each panel would be required at the service point of the building..


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## Southeast Power (Jan 18, 2009)

LawnGuyLandSparky said:


> That's a big no-can-do around here. 1 service on a structure.


For sure we can do it here due to the different voltage needed.


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## SE Electric (Dec 26, 2017)

varmit said:


> NO, you can not do a service as you describe in your original post.
> These guys were really quick to let me know. :laughing:
> 
> 1.) If you "paralleled" 3 disconnects, Any one disconnect could bypass the others. Also, the load lugs would be energized from the connections at the 600 amp panel - EVEN WITH THE DISCONNECT OFF unless all were off. A disconnect must disconnect all power in the circuit down stream of the disconnect.
> ...


 It sounds like you just replied to my original post. Any chance I could get you to read the whole thread?


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## telsa (May 22, 2015)

SE Electric said:


> I'm about to do a 600A service install for a company and just wanted to run my game plan by some people with more experience than me. It's a pad mount transformer feeding in from the POCO. I'm trenching ~330 feet and running 3 parallel runs of 350 al xhhw for the ungrounded conductors, and 1/0 al xhhw for the neutral piped in 3" sched 40 pvc. Jumping up into 3 200A disconnects (600V 600A disconnects are effin expensive!) outside the building and running 2-1/2" EMT inside into a panel with a 600A main.
> Am I screwing up on any of my calcs for sizing?
> Any thoughts on how to do it cheaper/easier?
> Reasons not to downsize the neutral?
> Should I find a new career?:vs_laugh:


Crazy to down-size the neutral.

OVER size the PVC. 

Plastic is dirt cheap vs any labor burn. 

It's the ditch that's expensive

I'm in EUSERC land, so I'm biased.

Forgive me, then. :notworthy:


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## telsa (May 22, 2015)

MTW said:


> I don't get the 3 disconnect thing either. Here that service would be CT metered, either at a CT cabinet or right at the padmount itself.
> 
> I would do as others have suggested - a 600 amp main outdoors or use a 600 amp main breaker in your MDP. Ask your supplier to put together a gear package and you will get better pricing.


THIS is much closer to the design I'd expect.

Forget about trying to out-manuver the NEMA players.

Design for CLEANLINESS... simplicity.

You should be CLONING other existing 600A 480Y277 Services that are in your Poco's area.

BTW, do you even have their 'green book' ?

( Could go by other colors -- it's your Poco's standards for ANY Service. This puppy would go down in flames, IMHO. )

&&&

STOP trying to win a bid based upon materials.

You win the cost battle by being astoundingly clever and efficient in your build.

THAT'S the 'game.'

You are actually going down the wrong road.


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## Southeast Power (Jan 18, 2009)

telsa said:


> THIS is much closer to the design I'd expect.
> 
> Forget about trying to out-manuver the NEMA players.
> 
> ...


It takes a few mistakes to learn how to be competitive on these.
I had a residential 600 amp open delta years ago. It was a long run too. over 300'.
The directional boring contractor we hired had to go under a clay tennis court and a six car driveway. 
It was parallel 500s with parallel 250 for the highleg and parallel 250s for the neutral if I remember correctly.
The UG contractor installed 3" I wasn't too happy about that.
I offered them $500 if they pulled and we fed.
It didn't take long. They had a cable pulling rig on the back of a truck that was a boom winch and steel cable.


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