Switchgear and panelboard section 408

hhsting

Senior Member
NEC 2017 408 part II says switchgear and switchboard and 408 part III is about panelboard.

Part III 408.36 exception allows MLO panelboard does not have to have individual protection for panelboard if its service equipment multiple disconnects 230.71.


Also note part III 408.36 first paragraph says if panelboard is not service equipment then overcurrent protection shall be provided not greater than rating of Panelboard


Where is all the above for switchboard and switchgear 408 part III?

Questions:

1. Does this mean that switchgear that is NOT service equipment can be provided by breaker higher than its rating? For example MLO switchgear NOT service equipment is 1000A bus but up stream breaker can be 1200A trip? If no then I don’t see it in 408 part II?

2. Does this mean that switchgear that IS service equipment is exempt or not like panelboard is for 408 part III 408.36? If it is then where is it in 408 part III or is it somewhere else in NEC 2017?
 
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hhsting

Senior Member
NEC 2017 408 part II says switchgear and switchboard and 408 part III is about panelboard.

Part III 408.36 exception allows MLO panelboard does not have to have individual protection for panelboard if its service equipment multiple disconnects 230.71.


Also note part III 408.36 first paragraph says if panelboard is not service equipment then overcurrent protection shall be provided not greater than rating of Panelboard


Where is all the above for switchboard and switchgear 408 part III?

Questions:

1. Does this mean that switchgear that is NOT service equipment can be provided by breaker higher than its rating? For example MLO switchgear NOT service equipment is 1000A bus but up stream breaker can be 1200A trip? If no then I don’t see it in 408 part II?

2. Does this mean that switchgear that IS service equipment is exempt or not like panelboard is for 408 part III 408.36? If it is then where is it in 408 part III or is it somewhere else in NEC 2017?

Any input?


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brantmacga

Señor Member
Location
Georgia
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Electrical Monke
408.30 says the panelboard must have a rating at least equal to the supply feeder or calculated load.


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augie47

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Tennessee
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State Electrical Inspector (Retired)
I think the point raised is that in Part III of Art 408, 408.;30 allows for a 6 disconnect MLO service panelboard but there is no corresponding wording in Part II for switchboards yet prior to 2020 it was common for switchboards.
 

don_resqcapt19

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Location
Illinois
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retired electrician
There is no specific requirement for overcurrent protection for switchboards or switchgear. The only limitations on the number of service disconnects in a switchboard or in switchgear are those found in Article 230.
 

augie47

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Tennessee
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State Electrical Inspector (Retired)
Makes sense ! When "he" first asked the question in another thread I was thinking about the exception for panelboards allowing the "six disconnect" rule and noted there was no such exception for switchboards but, as you point out, there is no switchboard exception needed as there is no requirement for a main with a switchboard as there is with a panelboard.
 

hhsting

Senior Member
There is no specific requirement for overcurrent protection for switchboards or switchgear. The only limitations on the number of service disconnects in a switchboard or in switchgear are those found in Article 230.

Really? So let me understand if you have following situation:


MLO 1000A switchgear fed from 1200A trip breaker located in same building with 1200A feeder cables then this would be okay? I would not meed to change the breaker to 1000A or lower trip?
 

don_resqcapt19

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Illinois
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retired electrician
Really? So let me understand if you have following situation:


MLO 1000A switchgear fed from 1200A trip breaker located in same building with 1200A feeder cables then this would be okay? I would not meed to change the breaker to 1000A or lower trip?
is this service equipment?
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
Conductors, including those in switchboards, need to be protected at there ampacity.
If you want code references look in110, 240, and 408.
 

hhsting

Senior Member
It must still be protected by limiting it's loading.

I dont see how MLO Service Switchboard and their line side bus from 6 main service breakers inside the service switchboard considered service entrance conductor or service conductor? Those buses are not feeders either so where is it you are getting this from?


Also i dont see anything in Part II NEC 408 stating what you are saying for switchboard?
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
Is your switchboard UL Listed as service equipment?
Then you need to install and protect it per article 110. UL has specific procedures for addressing the line side components in a service entrance switchboard.

Do you agree the bussing inside of a switchboard is a conductor?
If it is connected directly to the utility how can they be anything other than service conductors, just like the line side bussing in a meter main. Have you read the definitions in article 100?
 

hhsting

Senior Member
Where there are multiple service OCPDs, the only protection for the line side service conductors is the load calculation. There is no limit on the sum of the ratings of the multiple service OCPDs.

Code says that for service entrance conductors, their is exception for that for service MLO panelboard 408 part III bit nothing for service switchboard MLO?

Where is what you are saying in code for service switchboard bus MLO?
 

hhsting

Senior Member
Is your switchboard UL Listed as service equipment?
Then you need to install and protect it per article 110. UL has specific procedures for addressing the line side components in a service entrance switchboard.

Do you agree the bussing inside of a switchboard is a conductor?
If it is connected directly to the utility how can they be anything other than service conductors, just like the line side bussing in a meter main. Have you read the definitions in article 100?

Yes switchboard is UL listed. Definition of service is that provided by utility.


Is the service switchboard internal bus provided by utility? Nope utility conductors terminate on the bus lug but bus itself is not service conductor
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
Code says that for service entrance conductors, their is exception for that for service MLO panelboard 408 part III bit nothing for service switchboard MLO?
You don't have a panelboard, therefore these parts of 408 are not applicable to your installation. Please stop referring to them.
 

jim dungar

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Location
Wisconsin
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Retired Electrical Engineer - Power Systems
Yes switchboard is UL listed. Definition of service is that provided by utility.


Is the service switchboard internal bus provided by utility? Nope utility conductors terminate on the bus lug but bus itself is not service conductor
Who says the utility provides the service conductors? In my experience the conductors between the metering point and the service entrance equipment is provided by the owner/electrician.
 
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