service conductors size

[ohmhead]

I have a 2500amp main service disconnect the wire size called out by engineer states 6 x 600 mcm alu which is 2040amps whats the rule on breakers can the rating be adjusted if engineer agrees to lowering ampacity . Can we lower the rating of the breaker by code ?

 

[infinity]

What is the calculated load of the service? If it's 2000 amps or less and you use a 2000 amp main then you should be good.

 

[augie47]

A look at 240.6(B) & (C) {'11 Code} on adjustable trip breakers might be worth the read.

 

[ohmhead]

Thanks the engineer lowered the ampacaty to 2000 amps the demand load was 1575amps so the 2500 amp trip unit was adjusted thanks for the input .

 

[infinity]

Thanks the engineer lowered the ampacaty to 2000 amps the demand load was 1575amps so the 2500 amp trip unit was adjusted thanks for the input .

Sounds like a good solution unless the customer was paying for 2500 amps.

 

[ohmhead]

What is the calculated load of the service? If it's 2000 amps or less and you use a 2000 amp main then you should be good.

The calculated load is 1700 amps but the engineer states on dawning's 2500 amps on main breaker of gear .

 

[infinity]

The calculated load is 1700 amps but the engineer states on dawning's 2500 amps on main breaker of gear .

So code wise a 2000 amp OCPD would work but if they want the full 2500 amps then you need to make a change to the conductors. 6 sets of 600 kcmil copper would work or 7 sets of 750 kcmil Al.

 

[iwire]

The calculated load is 1700 amps but the engineer states on dawning's 2500 amps on main breaker of gear .

Wait, there are engineered drawings?

What size conductors do they show?

 

[infinity]

Wait, there are engineered drawings?

What size conductors do they show?

According to the OP "6 x 600 mcm alu which is 2040amps".