Overcurrent protection over 800 amp for services

[dm9289]

For a commercial apartment building with a calculated load of 1135 amps.

if you had 90c terminals could you use 3 sets of 4- 600kcm aluminum in different 4" pipes (3 hots and neutral).

600kcm@380 amps x 3 =1155. Plus use the next size up breaker at 1200amps.

In my mind I thought for this situation you were not permitted to use next size up breaker, help please?

 

[jap]

Who told you, you could use the next size up above 800 amps?

JAP>

 

[dm9289]

Who told you, you could use the next size up above 800 amps?

JAP>

No one I do not think you can per 240.4C but I did not know if that applied to UG service entrance conductors

 

[jap]

The rule is based on the rating of the overcurrent device, not conductors.

JAP>

 

[jim dungar]

No one I do not think you can per 240.4C but I did not know if that applied to UG service entrance conductors

Service conductor sizing is determined by the POCO not the NEC.
Are these really service entrance conductors? Anything after the service point is subject to the NEC.

 

[dm9289]

Service conductor sizing is determined by the POCO not the NEC.
Are these really service entrance conductors? Anything after the service point is subject to the NEC.

Underground goes from transformer to connection doghouse POCO UG. These cables exit the connection point and terminate in the 1200 amp panel.

 

[augie47]

Misconception could have arisen from the fact that if you were dealing with a situation other than a 1200 main OCP device (like the "six circuit rule" prior to 2020)_ you could have used the 1155 rated conductors.

 

[infinity]

3 sets of 600 kcmil Al is equal to 1020 amps (340*3=1020) since you would use the 75° C ampacity.

 

[dm9289]

It will have 90c terminations

 

[jap]

3 sets of 600 kcmil Al is equal to 1020 amps (340*3=1020) since you would use the 75° C ampacity.

He mentioned IF using 90 d terminals.

JAP>

 

[augie47]

ooops... missed that. Thanks infinity
I don't think he would have a gear with 90° terminations..... lugs maybe but not terminations.

 

[infinity]

It will have 90c terminations

He mentioned IF using 90 d terminals.

JAP>

That is irrelevant because whatever it's connect to will only be rated for 75° C.

 

[jap]

That is irrelevant because whatever it's connect to will only be rated for 75° C.

The spades on a padmount transformer? and who knows what on the other end?

JAP>

 

[infinity]

and who knows what on the other end?

The OP says it is feeding a commercial apartment building. Are you saying that a 1200 amp service in an apartment building could possibly have service equipment rated at 90° C? I can answer that, no.

 

[dm9289]

The spades on a padmount transformer? and who knows what on the other end?

JAP>

1200 amp main disconnect

 

[dm9289]

The OP says it is feeding a commercial apartment building. Are you saying that a 1200 amp service in an apartment building could possibly have service equipment rated at 90° C? I can answer that, no.

Thank you some lug changes were suggested, but waiting on the cut sheet on the main disconnect enclosure. I strongly suspect equipment will be 75c also.
But in principle can you use next size up on breaker for main disconnect
Example incoming cable 1155 amps
Main breaker 1200
I thought that might be 240.4C issue but was unsure for services

 

[infinity]

Thank you some lug changes were suggested, but waiting on the cut sheet on the main disconnect enclosure. I strongly suspect equipment will be 75c also.
But in principle can you use next size up on breaker for main disconnect
Example incoming cable 1155 amps
Main breaker 1200
I thought that might be 240.4C issue but was unsure for services

No the next size up rule ends at 800 amps. You'll need a minimum of 1200 amps worth of conductors for a 1200 OCPD.

 

[don_resqcapt19]

Thank you some lug changes were suggested, but waiting on the cut sheet on the main disconnect enclosure. I strongly suspect equipment will be 75c also.
But in principle can you use next size up on breaker for main disconnect
Example incoming cable 1155 amps
Main breaker 1200
I thought that might be 240.4C issue but was unsure for services

Changing the termination lugs does not change the temperature rating of the equipment. Very often the lugs on 75°C are rated at 90 or even 105 because they are standard lugs.

 

[jap]

The OP says it is feeding a commercial apartment building. Are you saying that a 1200 amp service in an apartment building could possibly have service equipment rated at 90° C? I can answer that, no.

Is a crimpon lug bolted to a transformer spade or bussbar a 75d connection?

JAP>

 

[infinity]

Is a crimpon lug bolted to a transformer spade or bussbar a 75d connection?

JAP>

I doubt it but maybe it is, I don't know. Regardless that point is moot since in this installation the equipment on the other end is only rated for 75° C.