# 1200amp service 3 phase 4 wire AL, 3 750kcmil runs or 6 4/0 runs?



## Math123 (Jun 16, 2018)

Ok so previously we've set up a 1200amp service using 3 750kcmil runs in 3 4" PVC (forgot which schedule but let's assume 40). 
Now different project and company we're setting up 1200amp with 3 conduits 4" sched 80 PVC and 2 runs (200amp each) of 4/0 AL 4 wire (3 phase) per conduit.

My question is, assuming same conduit is used is there a benefit of one method of delivery vs the other? (assuming same length run)


I'm not sure if I'm being clear enough but I can't figure out which approach is best from a safety or cost perspective. I'm sure one way has to be better than the other


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## brian john (Mar 11, 2007)

3 conduits 2-sets of 4/0, 8 conductors in each conduit?

I am assuming Copper?


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## Math123 (Jun 16, 2018)

brian john said:


> 3 conduits 2-sets of 4/0, 8 conductors in each conduit?
> 
> I am assuming Copper?


Sorry wasn't clear, 3 pipes, each pipe has 2 sets of cables, so 6 sets of cables total. Each cable set has 4 CCC (3 phase w. N). It's 4/0 AL, and it turns out to be 200amps per set of cables. So 200x6 sets (3 pipes with 2 sets in each) =1200amps.


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## telsa (May 22, 2015)

Such affairs are usually decided by the equipment that you must terminate into. A lot of gear just can't accept that many conductors. It's set up for just 750kCMIL.

Getting alternate lugs may prove impossible -- especially in your time horizon.

As for engineering to save a buck, it almost never pays off. The customer wants ALL of the savings. You can do all of the work, though. They're fine with that.

Pulling more than four CCC plus a grounding conductor (into one pipe) is a TRICK for most pulling crews. They're not used to it. The set-up will prove to be much more elaborate. 

This decision should've been made during the underground rough-in.

BTW, be ULTRA careful during the termination of so many angry snakes coming out of one pipe. Haste makes for bolted shorts. Boom!

BTW, I've never used Schedule 80 for a buried run in my life. It must really be tough in Jersey.


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## Math123 (Jun 16, 2018)

This is actually a PA project, I'm not questioning the engineers or whoever came up with the plan I'm just labor power, but knowing the difference will make a difference when I'm the one deciding those things. I like knowing why I do things as opposed to just doing them and not understanding why. Your reasons just make it super clear to me why it's better to run 750s which is great. You helped me gain understanding thank you!


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## Southeast Power (Jan 18, 2009)

We have been buying colored quadplexed conductors. I'm not a big fan of 750s or 8 conductors in a conduit or sch 80.
I'm thinking 4 conduits for 1200 amps.
One we are designing now has a 600amp breaker and a 400 amp breaker on the generator.
We will be intercepting a 1200 amp service with 4- 3" sch 40, 350 copper.
I'll go out and back to the new main and ATS with 4- 3" with quadplexed 500s if I remember correctly.

Last table on the bottom:

https://www.southwire.com/documents/CU_AL_Ampacity_Chart_Final.pdf


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## MTW (Aug 28, 2013)

Last summer the contractor I worked for did a 12 unit condo building, all electric since the location had no gas available. Anyway, it was a 1200 amp 120/208 padmount service which we did as 3 runs of 750 AL in 4" PVC. Unfortunately the boss ordered everything as S80 by accident but told us to run it anyway, which we did. The 750 AL was not really that hard to to work with and certainly much better than copper. Copper is just about out of the question for most jobs these days. We pulled it in with a bucket truck without issue.


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## Math123 (Jun 16, 2018)

MTW said:


> Last summer the contractor I worked for did a 12 unit condo building, all electric since the location had no gas available. Anyway, it was a 1200 amp 120/208 padmount service which we did as 3 runs of 750 AL in 4" PVC. Unfortunately the boss ordered everything as S80 by accident but told us to run it anyway, which we did. The 750 AL was not really that hard to to work with and certainly much better than copper. Copper is just about out of the question for most jobs these days. We pulled it in with a bucket truck without issue.


 also not exaggerating (too lazy to do the math) in a long run we had to do, copper would have used like $10+k more than using aluminum , I think it might have been a LOT more. Putting it into those terms I can see how we take our risks to save $ and factor the risk of loss vs the money saved the same way insurance actuaries don't see deaths as individuals dying but as a statistical number, and recall analysis see deaths per $ as a factor before they decide if they're doing a recall or not. We do it by using a wire more prone to failure, arcing, heat, shrinking and expanding (forgot the word for that) and fires. Makes me feel bad but also makes me resent actuaries less now.


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## Math123 (Jun 16, 2018)

That was a great doc, I actually saved it on my drive for future reference thanks! I think I'm going to make myself a binder with useful references for the field with the "best of", one day. Not today, but one day.


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## Math123 (Jun 16, 2018)

Math123 said:


> brian john said:
> 
> 
> > 3 conduits 2-sets of 4/0, 8 conductors in each conduit?
> ...


BTW this was wrong its 3 CCC 120/208, it matters for derating so I guess from a thecnical perspective, not a financial or practical one but I just learned that and wanted to correct it. The neutral carries unbalanced load only in this one.


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## joebanana (Dec 21, 2010)

MTW said:


> Last summer the contractor I worked for did a 12 unit condo building, all electric since the location had no gas available. Anyway, it was a 1200 amp 120/208 padmount service which we did as 3 runs of 750 AL in 4" PVC. Unfortunately the boss ordered everything as S80 by accident but told us to run it anyway, which we did. The 750 AL was not really that hard to to work with and certainly much better than copper. Copper is just about out of the question for most jobs these days. *We pulled it in with a bucket truck without issue.*



Whenever you use a motor vehicle to pull wire, there's an issue. Was that payback for the boss "accidentally" ordering the "wrong" wire?
Did he make you stage the pull on rebar, and ladders too? :surprise:


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## Southeast Power (Jan 18, 2009)

joebanana said:


> [/B]
> Whenever you use a motor vehicle to pull wire, there's an issue. Was that payback for the boss "accidentally" ordering the "wrong" wire?
> Did he make you stage the pull on rebar, and ladders too? :surprise:


It looks like the comment was about the Sch 80.
I was thinking the bucket truck had a winch and of course they were using a pull tension gauge.
Were you assuming they tired a rope to the tow hitch
??. :biggrin:


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## MTW (Aug 28, 2013)

joebanana said:


> [/B]
> Whenever you use a motor vehicle to pull wire, there's an issue. Was that payback for the boss "accidentally" ordering the "wrong" wire?
> Did he make you stage the pull on rebar, and ladders too? :surprise:


Ahh no. It was a material handling bucket truck and we tied the pull rope off to the boom, and simply lifted the boom up in the air right above the transformer pad. We fed at the meter stack side.


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## glen1971 (Oct 10, 2012)

Math123 said:


> Sorry wasn't clear, 3 pipes, each pipe has 2 sets of cables, so 6 sets of cables total. Each cable set has 4 CCC (3 phase w. N). It's 4/0 AL, and it turns out to be 200amps per set of cables. So 200x6 sets (3 pipes with 2 sets in each) =1200amps.





Math123 said:


> BTW this was wrong its 3 CCC 120/208, it matters for derating so I guess from a thecnical perspective, not a financial or practical one but I just learned that and wanted to correct it. The neutral carries unbalanced load only in this one.


I am not versed in the NEC, but do you need a ground conductor in the PVC as well? If so, that will increase your conductor count to 9 per conduit... (6 - CCC, 2 - N, 1 EGC)..

Again, with not being familiar with NEC but from what I saw with 4-6 CCC in a conduit you derate to 80%. 4/0 AL is good for 205 amps at 90C, which derated would be 164 amps.. 164*6= 984 amps of wire capacity... 

I'm wondering if there is some error in the OP's calculations, or if I misread the tables.. Can someone from south of the 49th can verify my numbers and tell me if I'm out to lunch?


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## Going_Commando (Oct 1, 2011)

glen1971 said:


> I am not versed in the NEC, but do you need a ground conductor in the PVC as well? If so, that will increase your conductor count to 9 per conduit... (6 - CCC, 2 - N, 1 EGC)..
> 
> Again, with not being familiar with NEC but from what I saw with 4-6 CCC in a conduit you derate to 80%. 4/0 AL is good for 205 amps at 90C, which derated would be 164 amps.. 164*6= 984 amps of wire capacity...
> 
> I'm wondering if there is some error in the OP's calculations, or if I misread the tables.. Can someone from south of the 49th can verify my numbers and tell me if I'm out to lunch?


You're right. I dont have my book in front of me but i'm pretty sure you have to sling 250 or 350 aluminum to meet ampacity, and as I recall you can't use the round up rule on more than 800A.


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## glen1971 (Oct 10, 2012)

Going_Commando said:


> You're right. I dont have my book in front of me but i'm pretty sure you have to sling 250 or 350 aluminum to meet ampacity, and as I recall you can't use the round up rule on more than 800A.


And 984 amps to 1200 is a heck of a round up... And the current I used was in the 90C column, so I'm assuming it will be less than that too...


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## Cow (Jan 16, 2008)

Math123 said:


> Ok so previously we've set up a 1200amp service using 3 750kcmil runs in 3 4" PVC (forgot which schedule but let's assume 40).
> Now different project and company we're setting up 1200amp with 3 conduits 4" sched 80 PVC and 2 runs (200amp each) of 4/0 AL 4 wire (3 phase) per conduit.
> 
> My question is, assuming same conduit is used is there a benefit of one method of delivery vs the other? (assuming same length run)
> ...



Are these service conductors terminating in a single 1200 amp overcurrent device or fuses?



If yes, you must have 1200 amps worth of conductors. 3-750 AL does not meet the requirements.


If no, then the conductors only need to be sized to carry the calculated load.


If we were looking at this, I'd most likely run (4)500 AL or (3)600 CU.


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## Southeast Power (Jan 18, 2009)

Cow said:


> Are these service conductors terminating in a single 1200 amp overcurrent device or fuses?
> 
> 
> 
> ...


Good catch!
Could be 6 - 200 amp mains.

Our engineer calculates the service conductors for the load.


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## joebanana (Dec 21, 2010)

Southeast Power said:


> It looks like the comment was about the Sch 80.
> I was thinking the bucket truck had a winch and of course they were using a pull tension gauge.
> Were you assuming they tired a rope to the tow hitch
> ??. :biggrin:


 Sure was. Especially with no mention of a winch, or tension gauge.
I've seen the insulation pull right off the conductors using a "pull truck", and air craft cable half hitches.
Somebody should invent a machine for pulling large wire. Something you could use in an electrical room, without all the noxious gas fumes. 

Like a motorized come-along. :wink:


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## joebanana (Dec 21, 2010)

MTW said:


> Ahh no. It was a material handling bucket truck and we tied the pull rope off to the boom, and simply lifted the boom up in the air right above the transformer pad. We fed at the meter stack side.


 Well, see there, if you hadn't wasted all that money on a bucket truck, you could have bought a nice tugger set up just for that purpose.
But I guess hydraulic power, over horse power, is a sure bet. jk


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## Math123 (Jun 16, 2018)

joebanana said:


> [/B]
> Whenever you use a motor vehicle to pull wire, there's an issue. Was that payback for the boss "accidentally" ordering the "wrong" wire?
> Did he make you stage the pull on rebar, and ladders too? :surprise:


LOL
when I read that the first time I assumed he meant he had to pull it with a bucket truck for an access issue, that obviously doesn't make sense considering the access requirements of the equipment, although I hate bucket work as is (it wobbles too much for the trucks I've been in) that's a mini life pro tip (actually pros would probably use a wire puller). I actually won't ever suggest it because it could break or someone could get hurt but if horrible accidents weren't a factor or safety wasn't a concern of mine I'd SOOO do that. And I thought I was slick for thinking of lifting material to a roof in a bucket truck and guiding it from down there. Any other awesome uses for equipment that it isn't listed or made for?


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## joebanana (Dec 21, 2010)

Math123 said:


> LOL
> when I read that the first time I assumed he meant he had to pull it with a bucket truck for an access issue, that obviously doesn't make sense considering the access requirements of the equipment, although I hate bucket work as is (it wobbles too much for the trucks I've been in) that's a mini life pro tip (actually pros would probably use a wire puller). I actually won't ever suggest it because it could break or someone could get hurt but if horrible accidents weren't a factor or safety wasn't a concern of mine I'd SOOO do that. And I thought I was slick for thinking of lifting material to a roof in a bucket truck and guiding it from down there. Any other awesome uses for equipment that it isn't listed or made for?


 I've used a scissor lift, and chains for setting wall mounted xfmrs.
The problem with (ab)using a bucket truck for unknown loads is, if you blow a seal, or hose, someone has to clean it up.


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## Math123 (Jun 16, 2018)

joebanana said:


> Math123 said:
> 
> 
> > LOL
> ...


I hate the navegation in this forum. Anyways, that's an awesome use, incredibly dangerous and irresponsible, I could see it tipping the equipment and possible taking someone with it who happens to get crushed by the lift or transformer when they fall out. But also it reminded me of how mechanics use chains to lift engines, practical tip I guess is, you can lift anything that your heart desires if you REALLY need to / want to. I'm a safety nerd, I don't want to become a case study lol, also I've traumatized myself into a healthy respect for safety rules by watching too many videos on YouTube of arc flashes, crushing and falling accidents and electrocution accidents from using aluminum or working live on high voltage and dropping the ball somewhere. Also if I die my wife is in trouble poor thing. Also I was wrong they're not running 6 sets of 4/0, but that misunderstanding definitely helped me gain valuable knowledge on many things. The pool of knowledge here is great. You guys are awesome.


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## glen1971 (Oct 10, 2012)

Math123 said:


> I hate the navegation in this forum. Anyways, that's an awesome use, incredibly dangerous and irresponsible, I could see it tipping the equipment and possible taking someone with it who happens to get crushed by the lift or transformer when they fall out. But also it reminded me of how mechanics use chains to lift engines, practical tip I guess is, you can lift anything that your heart desires if you REALLY need to / want to. I'm a safety nerd, I don't want to become a case study lol, also I've traumatized myself into a healthy respect for safety rules by watching too many videos on YouTube of arc flashes, crushing and falling accidents and electrocution accidents from using aluminum or working live on high voltage and dropping the ball somewhere. Also if I die my wife is in trouble poor thing. Also I was wrong *they're not running 6 sets of 4/0,* but that misunderstanding definitely helped me gain valuable knowledge on many things. The pool of knowledge here is great. You guys are awesome.


What is the final verdict on wire size and quantity?


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## Math123 (Jun 16, 2018)

Honestly I have no idea why this site is so glitchy in mobile, maybe it's an incentive to download the tap talk app or something. I can't even quote the message I waned to reply to. (I'm. Probably the issue tbh) 

As far as the wire is concerned, I don't know. I do know we are doing a temp lower amperage service for the meantime. That the POCO needs to upgrade the transformer before we can upgrade the current service to 1200amps, that we're actually using copper for the upgrade, that I need to learn my derating better, and most importantly that just because I see a wire it doesn't mean we're using it for that specific project. I made too many assumptions for the knowledge and experience I have. Maybe that's the most important thing lol. My ignorance is only surpassed by my ignorance, but knowing that keeps me trying to learn. 


Also to whomever said I needed 1200amps worth of conductor, is that bc I looked at the 90° chart for derating and I'm supposed to use the 75°? If so could I if I was the crappies lowest line electrician around use this 

"Separate Connector Provisions. Conductors terminating on independent pressure connectors on a bus, are permitted to be sized to the temperature rating of the connector. For example, if 90°*C pressure connectors are located on busbars, feeder conductors have a THHN insulation can be sized to the 90°*C temperature column of Table 310.16."

To run the lowest size possible wire for the long runs? 

I mean it feels like bad craftsmanship to try to use the minimum I can possibly get away with to meet the minimum requirements NEC sets, but if it's allowed it probably isn't as much of a danger as it seems right?


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## Math123 (Jun 16, 2018)

Cow said:


> Math123 said:
> 
> 
> > Ok so previously we've set up a 1200amp service using 3 750kcmil runs in 3 4" PVC (forgot which schedule but let's assume 40).
> ...



I might be mistaken (it was a long time ago and wire sizing was (still is but also was) way above my league to calculate and decide. If I remember correctly they did 165 feet (maybe 265) of the 750s hit a bladed disconnect (non fused? I don't remember seeing fuses I left before we finished ) then used copper from the monster disconnect to the main.


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## joebanana (Dec 21, 2010)

Math123 said:


> I hate the navegation in this forum. Anyways, that's an awesome use, incredibly dangerous and irresponsible, I could see it tipping the equipment and possible taking someone with it who happens to get crushed by the lift or transformer when they fall out. But also it reminded me of how mechanics use chains to lift engines, practical tip I guess is, you can lift anything that your heart desires if you REALLY need to / want to. I'm a safety nerd, I don't want to become a case study lol, also I've traumatized myself into a healthy respect for safety rules by watching too many videos on YouTube of arc flashes, crushing and falling accidents and electrocution accidents from using aluminum or working live on high voltage and dropping the ball somewhere. Also if I die my wife is in trouble poor thing. Also I was wrong they're not running 6 sets of 4/0, but that misunderstanding definitely helped me gain valuable knowledge on many things. The pool of knowledge here is great. You guys are awesome.


 It was a big lift, biggest one they rent. And safety was priority. Nobody under or around the load. 

I've done high voltage switching, including writing switching procedures for single banking sub-stations, industrial Co-generation, power distribution, and sub-station maintenance. NOTHING is ever done hot, except tripping out the OCB's, but that's done from the switch room. Dropping your balls is not an option.
Been doing this stuff for over 40 yrs. without a "lost time" injury, or OSHA recordable. I Have gotten sunburned though.
People who are unsafe don't last long in this trade.


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## varmit (Apr 19, 2009)

I do not know who sized these conductors for this service, but they are wrong. On any circuit with overcurrent protection rated over 800 amps, the conductors must be rated at or above the rating of the overcurrent device. See NEC 240.4 (C). 

In this case there would be two options using aluminum wire: 

Option 1: (3) 900 kcmil XHHW with neutral (min 250 kcmil) per 3 raceways. 
This would equal 1275 amps total for three runs at 75 C.

Option 2: (6) 350 kcmil XHHW with neutral ( min one 250 kcmil) per three 
raceways.This would equal 1200 amps at 75 C including derating for the 
more than three current carrying conductors. While code compliant, this 
would be a challenge to pull. 

As someone else mentioned, There may not be enough lug space in the service equipment for six lugs or wires of this size.


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