400A Meter Main Questions

[CFD925]

Hello All,

I have a question concerning the 2020 NEC Changes in 230.70, 230.71, specifically 230.71(B): Prior to 2020 NEC, a 400A meter Main allowed 2 x 200A Main Breakers in the same cavity/enclosure. According to the 2020 NEC, a change was made which required each 200A Breaker be separated either using a 400A Meter Socket and a 200A disconnect on each side or vertically with a partition. I have a guy that is arguing his "Old Style" 400A Meter Main with the dead front attachment is code compliant. Sorry, I can't insert the pictures like I wanted.

When the dead front removed, there are two 200A breakers in the same cavity/enclosure. There is a dead front attachment (like a "T" bar) from Square D and it does make the two switches into one switch, I get that. However, it does not provide any safety from arc flash or electrocution if the dead front is removed. In my mind and research, safety was/is the point of the code change. Square D is also saying the dead front attachment meets code. I don't see it!

I have found only one thread on here so far with info on this topic. 2020 NEC Changes to 230.71 Service Equipment Disconnecting Means Maximum Number of Disconnects | The Building Code Forum I've inserted this link of a Mike Holt interview which gives support to my point/question.

I will continue to research. Our plan reviewer and I have the same opinion. He's a 40 yr Master Electrician.

I'd like to hear from all of you concerning this matter.

Thank you for reading and anticipated reply!

Have a great weekend!

 

[Joe.B]

I agree with your interpretation. This was a significant change in the electrical code, and one that can slip under the radar pretty easily. As is usual, experienced installers, even the very best, make the assumption that the way they have been doing is still "code compliant" because they are unaware of the change. Whenever I get these kinds of arguments, I ask them to pull out their code book and show me.

"Oh, what's that? You don't have a current code book? Or any code book? Okay, let me get mine."

That usually does the trick.

 

[wwhitney]

What's the make and model number of the meter main?

Is this a new install? For existing equipment, the 2023 NEC adds an exception to 230.71(B):

Exception to (2), (3), (4), (5), and (6): Existing service equipment, installed in compliance with previous editions of this Code that permitted multiple service disconnecting means in a single enclosure, section, or compartment, shall be permitted to contain a maximum of six service disconnecting means.

Cheers, Wayne

 

[CFD925]

Thanks for the replies!

It's a new house. Square D RC816D400SL. The Dead Front attachment is CDK400.

 

[wwhitney]

This question came up on another forum:

2020 NEC Compliant 400A Common Disconnect Kit

Good morning, my AHJ has received a request if this "common disconnect accessory kit" would be accepted to meet the requirements of the 2020 NEC 230.71B. Would you consider this to be a 2. Panelboards with a main service disconnecting means in each panelboard enclosure You could operate each...

forums.mikeholt.com

Seems like the question is whether the kit turns two separate disconnecting means into one single disconnecting means. 230.90(A) includes the text "Single-pole circuit breakers, grouped in accordance with 230.71(B), shall be considered as one protective device." So the idea that handle ties can turn multiple devices into a single device is present in Article 230. [The reference to 230.71(B) appears to me to be left over from the 2017 NEC's version of 230.71(B).]

Cheers, Wayne

 

[CFD925]

Wayne,

I see that side of the equation. Maybe this issue should have been addressed under NEC 230.70 Disconnects.

However, the kit is mounted to the face of the dead front. When removing the dead front, you still have two disconnecting means in the same cavity/enclosure which defeats the safety reasoning behind the 2020 code change (when this all started). The wording "separate enclosures" in 2020 and 2023 NEC 230.71(B)(1) makes me think of this 400A meter main by Siemans MK0402L1400SC or a 400A Meter socket with two separate 200A disconnects, one on each side. Both have two separate enclosures, 1 for each disconnecting means.

All in all, with the dead front removed from the Square D RC816D400SL, there still can be accidental arc flash and/or electrocution whether or not the kit is installed.

At the end of the day, I just want everyone safe and be able to go home!

 

[wwhitney]

However, the kit is mounted to the face of the dead front. When removing the dead front, you still have two disconnecting means in the same cavity/enclosure which defeats the safety reasoning behind the 2020 code change (when this all started).

Well, that raises the question of what the safety reasoning is. If you have a single disconnecting means in a single enclosure, then obviously there's still a risk if you remove the dead front while that disconnecting means is "on". So I presume you are supposed to turn off the disconnecting means before you ever take off the dead front. And then if you do, and the line side lugs on the disconnecting means are guarded, that's about as safe as you can make it without getting the POCO to kill the line side conductors.

But for the case of multiple disconnecting means in one enclosure, there is the additional risk that the user will turn off only the disconnecting means they are working on, then remove the dead front, and thereby be exposed to the live load side lugs of the other disconnecting means and any wires connected to them. So avoiding that possibility is my understanding of the point of 2020 NEC 230.71(B).

However, in the case in the OP, the CDK400 ensures that if you shut off one of the two breakers before removing the dead front, you must shutoff both. So I'm not seeing any increase in risk with that over a single breaker in one enclosure. In both cases you could remove the dead front before turning off the disconnect, and in both cases you could turn on a breaker after the deadfront is removed. Obviously you shouldn't do either of those.

In other words, what sequence of steps/interactions would be safe for a single breaker as a service disconnect, but would not be safe for a RC816D400SL + CDK400?

Cheers, Wayne

 

[CFD925]

Thanks again for providing additional insight Wayne! Well explained!! I'm getting it now.

My Dad always said I was hardheaded. Sometimes it shows more than others

Thanks again!!!

 

[ICE]

The 400 amp service panel with the pair of 200 amp breakers and a handle tie in order to meet the code is perhaps a suitable solution however, the common scenario that comes to mind is that of an ADU and a primary dwelling fed from the 400 amp service point. If there is a handle tie for the 200 amp breakers that serve the ADU and the primary dwelling.... well I suppose that you can see the conundrum this presents.