Max size sub panel

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slick 50

slick 50

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Does anywhere in the NEC regulate how big of a subpanel you can run off of a 200 amp main panel? Also, did they remove the 42 space maximum spaces of a loadcenter rule from NEC? I heard they were.....:smile:

Thanks,
Bob
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
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Yes, the 42 circuit limit lighting and appliance branch circuit panel has been removed in the 2008 NEC and there is no size restriction for a subpanel.
 
Pierre C Belarge

Pierre C Belarge

Senior Member
Location
Westchester County, New York
slick 50 said:
Does anywhere in the NEC regulate how big of a subpanel you can run off of a 200 amp main panel? Also, did they remove the 42 space maximum spaces of a loadcenter rule from NEC? I heard they were.....:smile:

Thanks,
Bob
Click to expand...


1. Size is limited based on the calculations as per Art 220.


2. This is not a 'one size fits all' scenario.
UL and the NEC have very specific requirements in relation to the number of overcurrent devices permitted in a panel/enlosure. One has to be aware of the listing of the product, as the listing of all the panels/enclosures has not been changed. Pay particular attention to the labeling with the equipment.
Also, make sure that there are no local codes to the contrary and make sure that your jurisdiction has adopted the 2008 NEC.
The manufacturers are catching up to speed, but not all have the listed products available for the US, the ones who do have limited numbers of panels and they are not all the same number of overcurrent devices (such as 54, 60, etc...).
 
don_resqcapt19

don_resqcapt19

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Location
Illinois
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retired electrician
slick 50 said:
... Also, did they remove the 42 space maximum spaces of a loadcenter rule from NEC? I heard they were.....:smile:
Thanks,
Bob
Click to expand...
Yes they did, but it does not change the listing of existing panels. You are still required to comply with the panel label the states the maximum number of breakers.
 
C

cpal

Senior Member
Location
MA
slick 50 said:
Does anywhere in the NEC regulate how big of a subpanel you can run off of a 200 amp main panel? Also, did they remove the 42 space maximum spaces of a loadcenter rule from NEC? I heard they were.....:smile:

Thanks,
Bob
Click to expand...

I thought that there was a restriction on the maximum size ocpd ( Maybe 125-150A on a 200A buss) that could be connected to a panel buss. But I,m not sure. I would check the listing or instructions on the panel (load center) will take the ocp size you anticipate.
 
C

cpal

Senior Member
Location
MA
I guess it's not spelled out in UL so I'm really not sure now.



MAXIMUM SIZE FUSEHOLDERS OR CIRCUIT BREAKERS
58. If the ampacity of a branch bus bar or wire is less than the maximum current rating of any fuse
accommodated by a fuseholder it supplies, or if it is less than the current rating of any trip unit of an
interchangeable trip circuit breaker that it supplies, UL requires a clear and permanent marking, plainly
visible when the fuse or trip unit is being replaced. This prevents the use of a fuse or trip unit having more
ampacity than a bus bar or wire.
59. A panelboard with branch-circuit bus bars that permit adding a branch-circuit unit, circuit breaker,
switch, or fuseholder requires markings on the wiring diagram, the branch-circuit bus bars, or some other
location. Markings indicate the ampacity of the bus. This marking is not required if the ampacity of the bus
bar is not less than a) the maximum current rating of any unit to be connected to it; or b) the current rating
of the panelboard.
 
slick 50

slick 50

Senior Member
Location
6 super bowl ring city
cpal said:
I thought that there was a restriction on the maximum size ocpd ( Maybe 125-150A on a 200A buss) that could be connected to a panel buss. But I,m not sure. I would check the listing or instructions on the panel (load center) will take the ocp size you anticipate.
Click to expand...

Basically what I wanted to do is run a 200 sub from the 200 main. It just doesn't seem logical but if it is code compliant, rock and roll:) With the 42 circuit limit removed, I guess I can feed a 200 amp 40 circuit main lug panel with a 100 amp breaker also:confused: THANKS for all your input. This forum is a great tool!
 
acrwc10

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
active1 said:
I don't believe you'll find the words "sub panel" in the NEC
Click to expand...

Surprise it is in the second line of 409.2 (3) :D Now the subpanel people have there foot in the door who knows whats next.
 
A

active1

Senior Member
Location
Las Vegas
electricmanscott said:
There are many terms we use that are not in the NEC. :wink:
Click to expand...

Just saying there's no hierahy in panelboards. It's either service equipment or not.

Not tring to bust on anyone. The point is by using trade slang it can lead to misunderstandings by people learning.

slick 50 said:
Does anywhere in the NEC regulate how big of a subpanel you can run off of a 200 amp main panel? Also, did they remove the 42 space maximum spaces of a loadcenter rule from NEC? I heard they were.....:smile:

In the question it has some trade slang such as loadcenter, subpanel, and asks what the max panel you can feed off a 200a service panel. By just saying "no" a person might have the idea that there are special situations for load centers, sub panels, or a amprage limit as it pretains to the question.

The reality is there is no amprage limit except for as said calculated load, equipment ratings, and OCP. There is no special case for a load center as that's a marketing term, it's just a panel board. The 42 circuit breaker limit (other than main) in 2005 applied to all lighting and appliance branch circuit panel boards in any 1 cabinet. (408.35).
Click to expand...
 
A

active1

Senior Member
Location
Las Vegas
slick 50 said:
One more thing, if we can install a 200 amp branch breaker in a 200 amp main panel, does it need secured with a screw or bolt?:confused:

Basically what I wanted to do is run a 200 sub from the 200 main. It just doesn't seem logical but if it is code compliant, rock and roll With the 42 circuit limit removed, I guess I can feed a 200 amp 40 circuit main lug panel with a 100 amp breaker also
Click to expand...

You could just use a panelboard that uses feed thru lugs. The service panel main circuit breaker would then protect the feeder and 2nd panel.

If your looking at the residential plug in circuit breaker panels I don't think you'll find anything that will work. I think basic plug in CB panels have a branch CB of 100-125 limit (or at least limited by nothing made bigger than that size for the panel). A few have feed thru kits that clamp on where the breaker would snap into, but a limited by the manufacture to about 100a.

I want to say even many of the bottom end bolt-in panel boards don't have a 200a branch circuit breaker available. They could have a feed thru breaker or feed thru lug.

I would say you have 3 reasonable ways to do this:

1. A 225a bolt-in panel board with a 200a main & feed thru lugs. May be too costly if tis is a resi job.

2. Install two 200a main panels. Then you may need a way to connect two sets of service conductors to the meter. If existing this could be a lot of work. Also you have the question is the 200a meter adiquate for the load, do you need a larger service, will a single 200a disconect be required by AHJ.

3. By far the easiest and most cost effective. Use a 100a panel fed from the 200 amp service. Put the larger loads in the service panel and the lighter loads in the 100a panel. 100a panels are available in 30 space.

But back to basics you need to do the load calcs. If you really need two 200a panels than maybe the service is too small. If you just need the breaker spaces than add as many panels as needed as long as the load calcs are good.

Also a main lug panel can be feed with any size circuit breaker available as long as it dose not exceed the panelboards buss rating, and the feeder conductors.

I once gained an account because a different contractor pulled out a new 225a panelboard and breakers that was installed when units were sub devided. They told the landloard the 225 main lug panel was too big for the new 100a feed. They sold him another 225a main lug panel and breakers and told him it was a 100a panel. The landlord was not happly when I showed him the label on the panel door.
 
N

norcal

Senior Member
cpal said:
What edition NEC are you looking at??
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Here is a copy & paste from the 2008 NEC.

409.2 Definitions.
Control Circuit. The circuit of a control apparatus or system
that carries the electric signals directing the performance
of the controller but does not carry the main power
current.
Industrial Control Panel. An assembly of two or more
components consisting of one of the following:
(1) Power circuit components only, such as motor controllers,
overload relays, fused disconnect switches, and
circuit breakers
(2) Control circuit components only, such as pushbuttons,
pilot lights, selector switches, timers, switches, control
relays
(3) A combination of power and control circuit
components
These components, with associated wiring and terminals,
are mounted on or contained within an enclosure or
mounted on a subpanel. The industrial control panel does
not include the controlled equipment
 
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