# 800 amp 2X or 3X



## telsa (May 22, 2015)

3 1/2" is a size I just won't run.

2 x 750 kCMIL > 3 x 400 kCMIL.


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## RePhase277 (Feb 5, 2008)

The man hours running the extra conduit and terminating 4 more conductors would be more costly than the increased wire size, especially for aluminum, no?


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## Southeast Power (Jan 18, 2009)

RePhase277 said:


> The man hours running the extra conduit and terminating 4 more conductors would be more costly than the increased wire size, especially for aluminum, no?


The run is over 200' the difference between 3-1/2 and 3" is only about 20 per C.
It's about $1,2000 to drop a run of conduit and add about 300 for the cable up-side.
I'm not 100% on the labor.


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## Southeast Power (Jan 18, 2009)

RePhase277 said:


> The man hours running the extra conduit and terminating 4 more conductors would be more costly than the increased wire size, especially for aluminum, no?


Agreed but 750s are not friendly.


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## Cow (Jan 16, 2008)

I never liked 3.5". I always assumed only an engineer would spec that size since every supply house around here doesn't carry it.

So my answer is two 4" and 750's.

We've been buying our wire all on one spool but not quadplexed. We just had our new Maxis feeder brought out to our site, I haven't even used it yet. I have no doubt it'll process some 750's without any trouble. So I can't see handling 750's as too difficult unless you're feeding or pulling in some weird hard to access spot that requires a lot of manpower to get the cable where it needs to go.

Every time I use 750 AL instead of 500 CU, I know myself and the rest of the crew appreciate it at the end of the day!!!


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## MechanicalDVR (Dec 29, 2007)

Suncoast Power said:


> Agreed but 750s are not friendly.


Beat them into submission!


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## telsa (May 22, 2015)

Suncoast Power said:


> Agreed but 750s are not friendly.


No kidding, even in aluminum.


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## B-Nabs (Jun 4, 2014)

Yeah I'd be looking to run 3 x 400s myself.


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## ponyboy (Nov 18, 2012)

3" all day. 750 is just silly to work with even if it's aluminum. 3.5" is an odd size as well, any time I could've used it I went with 4" bc the fittings are easier to get. 


Sent from my iPhone using Tapatalk


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## chicken steve (Mar 22, 2011)

I'm curious as to why not dual 500's Sun dude , is 200' ft a VD issue....? ~CS~


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## RePhase277 (Feb 5, 2008)

chicken steve said:


> I'm curious as to why not dual 500's Sun dude , is 200' ft a VD issue....? ~CS~


Because 500 cu x 2 doesn't add up to 800 amps


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## Southeast Power (Jan 18, 2009)

chicken steve said:


> I'm curious as to why not dual 500's Sun dude , is 200' ft a VD issue....? ~CS~


It's aluminum.
I try to avoid larger copper if at all possible. 
I pulled my gizzard out playing around with some 500 cu 10 years ago and since then, if I have control of the design, it's going to be Aluminum.


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## Southeast Power (Jan 18, 2009)

RePhase277 said:


> Because 500 cu x 2 doesn't add up to 800 amps


380 + 380= 760. 

I've done that a few weeks ago. It works.


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## RePhase277 (Feb 5, 2008)

Suncoast Power said:


> 380 + 380= 760.
> 
> I've done that a few weeks ago. It works.


And 760 < 800. We got away with it for years. Then the inspectors went to a continuing education class and came back ready to fail every 400 amp feeder fed with 500 cu.


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## Southeast Power (Jan 18, 2009)

ponyboy said:


> 3" all day. 750 is just silly to work with even if it's aluminum. 3.5" is an odd size as well, any time I could've used it I went with 4" bc the fittings are easier to get.
> 
> 
> Sent from my iPhone using Tapatalk


That 750 al is just about the size of 600 copper and has a thicker insulation. I remember tha last time I worked with it, they, contrary to my specific ordering instructions, shipped the gear with 500 or 600 lugs. That put me in the lollipop business. To make it look nice, I lollipoped all 270 terminations in the gear.
I think I have a pic here somewhere.
Yes, you have to have a 3lb hammer for the make up.


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## chicken steve (Mar 22, 2011)

Suncoast Power said:


> 380 + 380= 760.
> 
> I've done that a few weeks ago. It works.


so why can't it work now?

>>>


> 240.4 Protection of Conductors.(B) Overcurrent Devices Rated *800 * Amperes or Less.


~CS~


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## chicken steve (Mar 22, 2011)

RePhase277 said:


> And 760 < 800. We got away with it for years. Then the inspectors went to a continuing education class and came back ready to fail every 400 amp feeder fed with 500 cu.


:no::no:
Methinks i'd fail them on being an inspector.....~CS~


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## Southeast Power (Jan 18, 2009)

RePhase277 said:


> And 760 < 800. We got away with it for years. Then the inspectors went to a continuing education class and came back ready to fail every 400 amp feeder fed with 500 cu.


I would tell them too bad. Either we follow the adopted code or we toss the whole thing.
Did they somehow produce a 380 amp fuse at that CE class?


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## RePhase277 (Feb 5, 2008)

chicken steve said:


> so why can't it work now?
> 
> >>>
> 
> ...


It can work, but you must calculate the load. If it is calculated to be less than 760 amps, you could use parallel 500 cu. If it is 761 amps or more, 500 won't cut it.


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## Southeast Power (Jan 18, 2009)

RePhase277 said:


> It can work, but you must calculate the load. If it is calculated to be less than 760 amps, you could use parallel 500 cu. If it is 761 amps or more, 500 won't cut it.


Yes, it does go by the load for sure but, usually you don't see a design that tight.


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## Cow (Jan 16, 2008)

Suncoast Power said:


> Yes, it does go by the load for sure but, usually you don't see a design that tight.


I agree. 2x500 CU is very common over here, I've done several 800 amp services in the last few years this way. Only one of them needed 2 x 600 CU for the full 800 amps.

More and more though, I'm using 2x750 AL just because it's much cheaper and easier.


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## TRurak (Apr 10, 2016)

Can you fit all that in one 4"?


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## TRurak (Apr 10, 2016)

I've also done four 3/0 copper in one 4". Easier to bend at termination points but I'm sure it is more expensive.


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## glen1971 (Oct 10, 2012)

TRurak said:


> Can you fit all that in one 4"?


Get all what in a 4"? 12 - 400's or 8 - 750's would be a 6" (Assuming a neutral from the quadplex reference).. Without the neutral it's at least a 5".. No derating was factored into that either... The labour would kill you on that one, is my guess.. And your guys would be borderline disgruntled, having to fight that much into one conduit for a day...



TRurak said:


> I've also done four 3/0 copper in one 4". Easier to bend at termination points but I'm sure it is more expensive.


Depending on insulation type, that's about a 2" or 2 1/2" conduit.. In a 4" conduit that should pull like butter! IMO...


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## chicken steve (Mar 22, 2011)

pg 70-756 , Chapter 9* notes* might be a consideration for pulling quadriplex..... not sure how 53% vs 40% would change the run....>>>



> (9) A multiconductor cable, optical fiber cable, or flexible
> cord of two or more conductors *shall be treated as a
> single conductor for calculating percentage conduit fill *
> area. For cables that have elliptical cross sections, the
> ...




~CS~


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## TRurak (Apr 10, 2016)

I didn't read that first post correctly, didn't see the aluminium. I meant four 3/0 per phase, not four total!


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