Tap feeding MLO Panelboard

[Ranger1]

I'm laying out a 600A 3 phase service. Due to the lack of availability of a 600A MDP, I'm considering a 600A 3 phase fused Service disconnect inside a building and then Tapping off to a 400A MLO. The fused disconnect would be fed via a trough so taps could be installed in the trough to feed the 400A MLO. The tap would be less than 10'. This is not my first choice but a 600A MDP is not available nor is the Main Breaker kit for the 400A Panelboard. In the future, a 200A MLO or MB panelboard could be installed if needed, using the same tap method.
Would the 400A and 200A Panelboards have to have main breakers?
I'm new to this forum and I don't see this specific topic mentioned prior. Thanks

 

[infinity]

Yes a main would be required. One code section:

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.

Exception No. 1: Individual protection shall not be required for a panelboard protected by two main circuit breakers or two sets of fuses in other
than service equipment, having a combined rating not greater than that of the panelboard. A panelboard constructed or wired under this exception shall not contain more than 42 overcurrent devices. For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively.

 

[don_resqcapt19]

While the language in 240.21(B)(1) can be read as permitting the proposed installation, the rule in 408.36 requires the panel to have overcurrent protection within or on the line side of the panelboard.

 

[hillbilly1]

What I’m having to do is using four 200 amp fusible disconnects tapped off a 800 amp disconnect, because 800 amp mb panelboards have a ten month lead time, same with the 200 amp mb panelboards. MLO I can get off the shelf easily. Had to go back and have the engineer redraw it for the inspection department.

 

[Ranger1]

Yes a main would be required. One code section:

Thank you for the prompt and clear response. I am not surprised by the answer but needed confirmation. These "supply chain issues" are creating a lot of problems for us. I hate to piece this together to make it all work without a MDP but it looks like I have no choice. Hopefully I'll have enough wall space. I ordered the MDP 4 months ago and just got an estimated delivery of August 1. The customer needs AC in the shop and more car chargers so I can't wait that long. Thanks again!

 

[infinity]

Thank you for the prompt and clear response. I am not surprised by the answer but needed confirmation. These "supply chain issues" are creating a lot of problems for us. I hate to piece this together to make it all work without a MDP but it looks like I have no choice. Hopefully I'll have enough wall space. I ordered the MDP 4 months ago and just got an estimated delivery of August 1. The customer needs AC in the shop and more car chargers so I can't wait that long. Thanks again!

You could use a 400 amp fused disconnect to feed the MLO panel from the feeder tap.

 

[Ranger1]

You could use a 400 amp fused disconnect to feed the MLO panel from the feeder tap.

I'm looking into that or an enclosed breaker. It's extremely disappointing to go from a nice clean job with a 600A MDP and then to a 600A FDS, a 400A FDS and a 400A Panelboard via taps. Down the road this will also require a 200A FDS and a 200A Panelboard via more taps. It just makes a mess of the job...