400a main question

[olly]

POCO's often offer a 320a self contained meter socket option, anything higher you typically have to have a CT cabinet.

I cannot find a 300a or 350a disconnect.

I have been told that you can use a 400a cold sequenced disconnect and a 400a main disconnect for the panel board because they are designed to trip at 320a. It sound legit because 80 percent of 400 is 320.

Can any one verify that this is allowable?

 

[augie47]

Common application.
As you can see on this cut-sheet, http://www.milbankworks.com/catalogs/u5890-5895.pdf , the socket is 320 amp continuous rating which would correspond to a 400 amp breaker's continuous rating

 

[kwired]

POCO's often offer a 320a self contained meter socket option, anything higher you typically have to have a CT cabinet.

I cannot find a 300a or 350a disconnect.

I have been told that you can use a 400a cold sequenced disconnect and a 400a main disconnect for the panel board because they are designed to trip at 320a. It sound legit because 80 percent of 400 is 320.

Can any one verify that this is allowable?

320 is rated 320 continuous. Kind of been mentioned already.

320 is also highest plug in type typically found - better say typically or someone will prove me wrong

Though not so common there are bolt in meters with higher capacity ratings, but most POCO do go with CT metering if more then a 320 can handle.

 

[meternerd]

320 is rated 320 continuous. Kind of been mentioned already.

320 is also highest plug in type typically found - better say typically or someone will prove me wrong

Though not so common there are bolt in meters with higher capacity ratings, but most POCO do go with CT metering if more then a 320 can handle.

Nope....you're right. Form 2S Class 320 240V meter is the replacement for the older single phase Form 2K 400A 240V bolt in. We use socket adapters that convert the 400A bolt in to a 320A socket. Still uses a 400A main. Over 400A requires CT's.

 

[ggunn]

... Over 400A requires CT's.

That number varies among AHJ's. Here in Austin anything over 225A requires CT metering.

 

[electrofelon]

POCO's often offer a 320a self contained meter socket option, anything higher you typically have to have a CT cabinet.

I cannot find a 300a or 350a disconnect.

I have been told that you can use a 400a cold sequenced disconnect and a 400a main disconnect for the panel board because they are designed to trip at 320a. It sound legit because 80 percent of 400 is 320.

Can any one verify that this is allowable?

Typically, 320/400 amp services will have 2 200 amp disconnects and two sets of service entrance conductors per NEC 230.40. This is much cheaper and more convenient that having a 400 amp main.

 

[meternerd]

That number varies among AHJ's. Here in Austin anything over 225A requires CT metering.

Same here, but only for commercial. Residential can use CL 320. If it's three phase, (they do make a CL 320 Form 9S 3 P, 4W) we require CT's over 200A. Quite a few homeowners here in the Tahoe area with large 120/240 loads such as hot tubs and huge houses. I kinda think they want the CL 320 service so they can brag to their neighbors how high end their "cabin" is.

 

[kwired]

That number varies among AHJ's. Here in Austin anything over 225A requires CT metering.

AHJ or POCO?

 

[ggunn]

AHJ or POCO?

In Austin they are one and the same; Austin Energy is a municipally owned utility.