400a Main breaker fed with 350mcm

[Mustang125]

See attached image. This is showing a 400a main breaker panel fed with 350mcm, wouldn't this need to be 600mcm by code?
See the attached image showing 350mcm feeding a 400a main breaker panel. This seems like it would need 600mcm by code, wouldn't it?

 

[infinity]

Yes the conductors are too small. Is the 400 amp "existing main disconnect" the service disconnect with overcurrent protection?

 

[petersonra]

Can probably be a 500 but where they came up with 350 escapes me. I would just ask them about it.

 

[Mustang125]

The existing main disconnect is a 400a fused disconnect

Yes the conductors are too small. Is the 400 amp "existing main disconnect" the service disconnect with overcurrent protection?

 

[Mustang125]

id prefer to use 500mcm, it always escapes me when can I

The existing main disconnect is a 400a fused disconnect

legally use 500mcm for a 400a service when 500mcm is only rated at 380 75degree?

 

[infinity]

The existing main disconnect is a 400a fused disconnect

So then it looks like the tap rules will apply to the new conductors feeding the nonfused disco from the wireway. Assuming the exiting conductors are 600 they would need to be 600 kcmil since the next size up rule cannot be used.

 

[ptonsparky]

Who owns the disconnect? POCO would change things.
We would never see a customer owned disconnect ahead of the meter here.

 

[ptonsparky]

What size fuses are in the disconnect?

 

[Mustang125]

I agree. Not exactly sure. We do see disconnects ahead if its 480v service "hot sequence" and no disconnect before "cold sequence" on 208v. But this is a very old install

Who owns the disconnect? POCO would change things.
We would never see a customer owned disconnect ahead of the meter here.

 

[Mustang125]

The existing main disconnect has 400a fuses in it.

What size fuses are in the disconnect?

 

[Mustang125]

the existing conductors leaving the main disconnect into the wireway where everything is tapping off are 500mcm copper

So then it looks like the tap rules will apply to the new conductors feeding the confused disco from the wireway. Assuming the exiting conductors are 600 they would need to be 600 kcmil since the next size up rule cannot be used.

 

[electrofelon]

id prefer to use 500mcm, it always escapes me when can I


legally use 500mcm for a 400a service when 500mcm is only rated at 380 75degree?

Fine due to the next size up rule.

 

[ptonsparky]

POCO may have supplied and own the secondary conductors. Not your problem. Still wouldn't hurt to ask questions because that new 400 you're putting in lowered the demand. Right?

 

[kwired]

Fine due to the next size up rule.

Plus load calculation can not be over 380.

 

[infinity]

the existing conductors leaving the main disconnect into the wireway where everything is tapping off are 500mcm copper

Then 500 kcmil should have been used instead of the 350's and you don't need the non-fused disconnect after the wireway.

 

[kwired]

POCO may have supplied and own the secondary conductors. Not your problem. Still wouldn't hurt to ask questions because that new 400 you're putting in lowered the demand. Right?

I believe he said those are 500's the 350's are feeding the equipment on the right of the diagram

 

[kwired]

Then 500 kcmil should have been used instead of the 350's and you don't need the non-fused disconnect after the wireway.

The disconnect after the wireway would allow you to disconnect the far right equipment without shutting the entire service down.

 

[infinity]

The disconnect after the wireway would allow you to disconnect the far right equipment without shutting the entire service down.

The new panels have a main so the disconnect is redundant and not required. It could be used as you've suggested to completely de-energized the new panels ahead of the main CB.

 

[ptonsparky]

the existing conductors leaving the main disconnect into the wireway where everything is tapping off are 500mcm copper

I believe he said those are 500's the 350's are feeding the equipment on the right of the diagram

I get 350s to the left of the equipment.

 

[kwired]

I get 350s to the left of the equipment.

Post 11, OP says they are 500 up to the gutter.