Meter/ Load center Tap conductors

[Johnhall30]

Can tap conductors feeding a dwelling unit meter/load center terminate into two overcurrent protection devices, or does this load center need to have a main breaker?

Alternatively, I could upsize the tap conductors and frame size to 200A where the total combined load of the breakers does not exceed 200A.

 

[electrofelon]

For a 25 foot tap (240.21(B)(2)) the tap conductors need to terminate on a single OCPD. For the 10 foot tap rule ((B)(1)) the wording isnt the best, despite being changed recently, but IMO you still have to terminate on a single OCPD.

 

[Johnhall30]

For a 25 foot tap (240.21(B)(2)) the tap conductors need to terminate on a single OCPD. For the 10 foot tap rule ((B)(1)) the wording isnt the best, despite being changed recently, but IMO you still have to terminate on a single OCPD.

Yes the wording in 240.21(B)(1) doesnt specifically state you need to terminate in a single OCPD. After more research I believe 408.36 requires make this case require a single OCPD.

408.36 Overcurrent Protection.
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.

 

[electrofelon]

Yes the wording in 240.21(B)(1) doesnt specifically state you need to terminate in a single OCPD. After more research I believe 408.36 requires make this case require a single OCPD.

408.36 Overcurrent Protection.
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.

IMO you dont need 408.36 to require a single OCPD for the tap, but yes it certainly comes into play for panelboards depending on the bus rating and the size of the OCPD protecting the feeder (you could have a tap supplying things other than panelboards such as switchboards that dont have that protection requirement).

Note there is an exception for the panelboard protection requirement for MLO service panels, but you have a feeder not a service.

 

[kwired]

240.21(B)(1)(1):

The ampacity of the tap conductors is


Not less than the combined calculated loads on the circuits supplied by the tap conductors, and


Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors.

Seems to me with the "(s)" that was a change in 2014, they intend to allow more than one overcurrent device, but pay attention to required conductor ampacity

408.36 has nothing to do with required ampacity of the tap conductor.

This only applies if this is a tap from a "feeder"

If these are service conductors the so called tap only needs to have ampacity equal or greater than calculated load connected to it when there are multiple service disconnects supplied by it.

 

[electrofelon]

Yes the wording in 240.21(B)(1) doesnt specifically state you need to terminate in a single OCPD. After more research I believe 408.36 requires make this case require a single OCPD.

408.36 Overcurrent Protection.
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.

240.21(B)(1)(1):



Seems to me with the "(s)" that was a change in 2014, they intend to allow more than one overcurrent device, but pay attention to required conductor ampacity

408.36 has nothing to do with required ampacity of the tap conductor.

This only applies if this is a tap from a "feeder"

If these are service conductors the so called tap only needs to have ampacity equal or greater than calculated load connected to it when there are multiple service disconnects supplied by it.

Thinking about it some more, and I agree you could land a 10 foot tap on a MLO panel if the ampacity of the tap is greater than or equal to the bus rating of the panel. The panelboard would be the "device" in the tap rule. But then 408.36 would get you so you would have to increase the bus rating (or decrease the feeder breaker setting) until is isnt a tap anymore.

 

[Johnhall30]

Thinking about it some more, and I agree you could land a 10 foot tap on a MLO panel if the ampacity of the tap is greater than or equal to the bus rating of the panel. The panelboard would be the "device" in the tap rule. But then 408.36 would get you so you would have to increase the bus rating (or decrease the feeder breaker setting) until is isnt a tap anymore.

Although it doesn't specifically say you have to land the 10' tap conductors into a single set of OCPD, it seems bad practice because the tap conductors aren't fully protected from overloading.

I would just backfeed a breaker into the MLO section of the load center and have it secured on per the NEC