# 800 amp 480/277 volt service



## Tom45acp (Sep 6, 2011)

chris29 said:


> What size wire is needed for an 800 amp service? I was thinking parallel 500 kcmil. but looking at an existing 800 amp srevice they used parallel 350 kcmil. Am I missing something?


No, you're not missing anything but the original installer & inspector sure did.

Keep in mind that if you want to use the full 800 amps, you'll need to bump the wire size up to 600kcmil or some other parallel combination that gets you to 800 amps.


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## BBQ (Nov 16, 2010)

chris29 said:


> What size wire is needed for an 800 amp service? I was thinking parallel 500 kcmil. but looking at an existing 800 amp srevice they used parallel 350 kcmil. Am I missing something?


Parallel 500 copper is allowed but really means you have a maximum 760 amp service protected by an 800 amp breaker.

Parallel 600 coppers will generally provide a true 800 amp service. 


Parallel 350 copper ... you got me. At best you have a combined ampacity of 620 amps and 240.6 shows a 700 amp as a standard size overcurrent device. It seems to me the largest breaker or fuse would be 700 amps.

Is there more than one service disconnecting means?


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## chris29 (Mar 28, 2013)

No other disconnecting means, from pole to main breaker parallel 350kcmil THHN,THWN2 cable.


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## NolaTigaBait (Oct 19, 2008)

chris29 said:


> No other disconnecting means, from pole to main breaker parallel 350kcmil THHN,THWN2 cable.


Are those the utilities conductors?


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## chris29 (Mar 28, 2013)

No, they are coming from the weatherheads into panel.


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## BBQ (Nov 16, 2010)

NolaTigaBait said:


> Are those the utilities conductors?


Good thought, seems like the only way it could have passed.


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## danickstr (Mar 21, 2010)

open air?:laughing:


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## chris29 (Mar 28, 2013)

No,they are ran through 2 sets of conduit and weatherhead,outside building in through wall.


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## cdslotz (Jun 10, 2008)

chris29 said:


> No,they are ran through 2 sets of conduit and weatherhead,outside building in through wall.


Then you don't have an 800A service


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## ponyboy (Nov 18, 2012)

cdslotz said:


> Then you don't have an 800A service


The breaker says otherwise lol. Did you check the load?


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## varmit (Apr 19, 2009)

The main breaker could be an 800 amp frame with a lower current chip installed.


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## ponyboy (Nov 18, 2012)

varmit said:


> The main breaker could be an 800 amp frame with a lower current chip installed.


possibly. i think the more logical explanation is that someone either didn't know wtf they were doing or knew exactly what they were doing and got away with it


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## Dash Dingo (Mar 3, 2012)

ponyboy said:


> possibly. i think the more logical explanation is that someone either didn't know wtf they were doing or knew exactly what they were doing and got away with it


I did a 1200 amp service a while back, inspector never opened the door on the gear to take a peek, never looked at the size of the main ground to the water pipe. All that he cared about was that I had a uffer ground and that it was accessible.


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## ponyboy (Nov 18, 2012)

Dash Dingo said:


> I did a 1200 amp service a while back, inspector never opened the door on the gear to take a peek, never looked at the size of the main ground to the water pipe. All that he cared about was that I had a uffer ground and that it was accessible.


i haven't done a service under 1200 in a while and the inspector has never once physically looked at the conductors. he'll just ask i used and that's the end of it.


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## njdvils99 (Mar 18, 2013)

ponyboy said:


> i haven't done a service under 1200 in a while and the inspector has never once physically looked at the conductors. he'll just ask i used and that's the end of it.


Damn, the inspectors out here put on the rubber glove. The bigger it is, the deeper they go. So needless to say we were walking kind of funny after putting in dual 480V 3000A services.

Back to the OP's question, you're not missing anything. Jut make sure you didn't get 500 MCM from using the 90 degree column. You'll need parallel 600's for 800A. What size are the conduits on the outside?


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## mbednarik (Oct 10, 2011)

As long as the calculated load is not more than 620 amps you are fine. I once got dinged on a 200 amp service, I ran 4/0 XHHW AL service conductors, but it was actually labeled 2/0 for about 200ft in the middle of the roll. I showed the inspector a piece of 4/0 and held it next to it, didn't fly. Had to yank out the 4/0 with the 2/0 label and pull in the correctly labeled wire. Supply house exchanged the 200ft of mismarked wire.


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## sbrn33 (Mar 15, 2007)

Dash Dingo said:


> I did a 1200 amp service a while back, inspector never opened the door on the gear to take a peek, never looked at the size of the main ground to the water pipe. All that he cared about was that I had a uffer ground and that it was accessible.


Does it have to be accessible?


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## cdslotz (Jun 10, 2008)

240.4 states that 800A or above breaker, the conductors it protects shall be greater than or equal to 800A. 
Around here they require (2) runs of 600 cu.


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## BBQ (Nov 16, 2010)

ponyboy said:


> i haven't done a service under 1200 in a while and the inspector has never once physically looked at the conductors. he'll just ask i used and that's the end of it.


When do you do a service?


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## BBQ (Nov 16, 2010)

mbednarik said:


> As long as the calculated load is not more than 620 amps you are fine.


No that is not correct,the next standard size breakers after 620 is 700, not 800.


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## BBQ (Nov 16, 2010)

njdvils99 said:


> Back to the OP's question, you're not missing anything. Jut make sure you didn't get 500 MCM from using the 90 degree column. You'll need parallel 600's for 800A. What size are the conduits on the outside?


Parallel 500s are allowed to be protected with an 800.


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## BBQ (Nov 16, 2010)

cdslotz said:


> 240.4 states that 800A or above breaker, the conductors it protects shall be greater than or equal to 800A.
> Around here they require (2) runs of 600 cu.


Damn it, I was thinking more than 800, not 800 and above.


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## HARRY304E (Sep 15, 2010)

BBQ said:


> When do you do a service?


I usually start just after sunrise....:laughing:


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## wildleg (Apr 12, 2009)

cdslotz said:


> 240.4 states that 800A or above breaker, the conductors it protects shall be greater than or equal to 800A.
> Around here they require (2) runs of 600 cu.


wrong


240.4
.
.
.
(B) Overcurrent Devices Rated 800 Amperes or Less.
The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following condi- tions are met:
(1) The conductors being protected are not part of a branch circuit supplying more than one receptacle for cord- and-plug-connected portable loads.
(2) The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rat- ing (but that shall be permitted to have other trip or rating adjustments).
(3) The next higher standard rating selected does not ex- ceed 800 amperes.

(C) Overcurrent Devices Rated over 800 Amperes. Where the overcurrent device is rated over 800 amperes, the am- pacity of the conductors it protects shall be equal to or greater than the rating of the overcurrent device defined in
240.6.


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## BBQ (Nov 16, 2010)

wildleg said:


> 240.4
> .
> .
> .
> ...


Thanks, hard to look up code on my IPad, the PDF reader sucks.


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## ponyboy (Nov 18, 2012)

BBQ said:


> When do you do a service?


i add services to existing facilities i contract with. not many though, i did six 3000 amp and a couple 2000 amp last year between six buildings


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## cdslotz (Jun 10, 2008)

wildleg said:


> wrong
> 
> 
> 240.4
> ...


Yes, after re-reading this you are correct. I only see designed riser diagrams, and I never see (2) runs of 500 for 800A anymore.

Side note, 800A is always the hardest size to convert to AL. To keep it with (2) runs you have to use 900kcmil


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## chris29 (Mar 28, 2013)

So is it more practical to run the 2 runs of 600's in parallel = 840 Amps or run 4 runs of 250's in parallel = 816 Amps. Which would be easier to pull through the conduit? probably be about 60 ft pulls.


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## ponyboy (Nov 18, 2012)

chris29 said:


> So is it more practical to run the 2 runs of 600's in parallel = 840 Amps or run 4 runs of 250's in parallel = 816 Amps. Which would be easier to pull through the conduit? probably be about 60 ft pulls.


It's more practical to pull 500s if you don't need the true 800 amps. Have you done a load calc?


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## Rob DeJonge (Apr 1, 2021)

Parallel 500's by code is the correct size for 800A. 240.4 says up to 800A you can go up to the next standard OCP. I see some statements on here about "true 800A" needing 600s. This isn't true. The amperage is determined by the load. The code says you need a certain size due to insulation degradation caused by heat which is caused by resistance. You can get 800A on #12's until it bursts into flames. One consideration which may require 600s is the distance the feed is running. Generally you don't want to exceed 3% voltage drop. One other trick one is for 4 wire wye systems where you feed non-linear loads like VFDs. In this case you must count the neutral as a current carrying conductor which makes it 4 so you must de-rate to 80% column. This means you must use 600s for the 800A feed.


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## MotoGP1199 (Aug 11, 2014)

@Rob DeJonge 

This thread is from 2013. With the sites new format it is easy to get sucked into old threads by looking at the recommended reading at the bottom.


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