Disconnecting Means

[blvengineers]

Guys I think I have misunderstood the code as it relates to disconnecting means. I have a 2000A 480Y/277, 3 phase 4 wire distribution system. I have individual distribution cabinets placed throughout the facility. Is it legal to make the downstream distribution panels main lug only? Does the code not require disconnecting means if not within 25 feet line of site. I really need to get this answered before my bid date. Also, this may cause a coordination problem with the source breaker in the MSDB and the main breaker in the HDP panel.

 

[Dennis Alwon]

These articles may help. You can have up to 6 disconnects. Thus a main distribution panel can be main lug but the max number of discos must be six. More than 6 then a main disconnect is required.

230.70 General.
Means shall be provided to disconnect all conductors in a building or other structure from the service-entrance conductors.
(A) Location. The service disconnecting means shall be installed in accordance with 230.70(A)(1), (A)(2), and (A)(3).
(1) Readily Accessible Location. The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors.

230.71 Maximum Number of Disconnects.
(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception No. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be not more than six sets of disconnects per service grouped in any one location.
For the purpose of this section, disconnecting means installed as part of listed equipment and used solely for the following shall not be considered a service disconnecting means:
(1) Power monitoring equipment
(2) Surge-protective device(s)
(3) Control circuit of the ground-fault protection system
(4) Power-operable service disconnecting means

 

[walkerj]

Dennis' statements are correct, but I believe you were asking about the downstream panels.
A disco is not required at the remote panelboards.
The breakers serving the panels will do just fine

 

[charlie b]

I am not certain I understand the question. This part has me confused:

I have a 2000A 480Y/277, 3 phase 4 wire distribution system. I have individual distribution cabinets placed throughout the facility.

Are you talking about the disconnecting means for removing power from a building? Or do you have that covered in your (single) main service panel, and are you talking about distribution and branch panels downstream from the main?

Once you hit the first overcurrent device (either outside or inside the building), the "six throw rule" and the "grouped together rule" no longer apply. You do need a breaker in the main panel, to protect the next panel downstream and to protect its feeder as well. But you do not need a main breaker in the downstream panel, as others have already said.

 

[Cold Fusion]

I have a 2000A 480Y/277, 3 phase 4 wire distribution system.

Is it legal to make the downstream distribution panels main lug only?

I really need to get this answered before my bid date.

The code issues have been excellently answered. However I have a curiosity question. Keep in mind, my work is all industrial.

I'm really curious as to why you would be asking. Normally, I'm working with the owners to figure out what they want/need. Code minimums usually don't have much bearing on the decision. None of my customers would be interested in shaving a few bucks just because the code said they could. If they wanted/needed a main CB for maintenance, convenience, or even just because they think they want one - it would go in.

So, I'm wondering, is this a design-build and the owners want as cheap as they can get? I'm absolutely not against taking money from customers that want cheapest they can get. If that was what they speced - that's what they would get. They got the money - they get to make all of the decisions. However, it would be surprising for industrial.

cf

 

[Cavie]

Guys I think I have misunderstood the code as it relates to disconnecting means. I have a 2000A 480Y/277, 3 phase 4 wire distribution system. I have individual distribution cabinets placed throughout the facility. Is it legal to make the downstream distribution panels main lug only? Does the code not require disconnecting means if not within 25 feet line of site. I really need to get this answered before my bid date. Also, this may cause a coordination problem with the source breaker in the MSDB and the main breaker in the HDP panel.

Sub panels need not have main breakers. These are not concidered Disconects. the equipment wired to these panels would require disconects if not within sight of the sub-panel.

 

[Keri_WW]

I've always made my panels MCB if they were in a different room than the panel feeding it. I learned this from my first mentor when I began learning how to design. I've noticed lately that its pretty mixed as to whether or not a designer will add a MCB or just go MLO (especially with the guys in my office). If it is not code required, under what circumstances would you want to use a MCB?

I never really questioned why when I was taught that, just figured it would be a good idea to have it so that you could drop off the entire panel from that one location.