30A breaker feeding a 100A sub-panel?

I was visiting my brother's house during some basement remodeling, and noticed that the electrical contractor had added a 100A loadcenter to feed the new basement lights, etc.
The new 100A loadcenter is fed via a 30A double-pole breaker in in one of the home's original two loadcenters. This struck me as being odd. After consideration, it would seem that (as long as wires are properly sized) it is not unsafe electrically but what does the electrical code specifiy?
Also, I would anticipate nuisance tripping of the 30A breaker feeding the sub-panel, since there are several 15A and 20A breakers in the sub-panel and even if a few are run near max it would exceed the 30A breaker rating.
Thoughts, anyone?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
He had a 100 amp panel but not a 30.
--
Joseph Meehan

Dia \'s Muire duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

probably not a issue unless all loads are on all the time.
take a look at most main panels, 100 amp main with at least 20 or perhaps more 20 amp breaker slots.
what his mains capacity?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Not a problem at all. The "100a" just refers to the maximum you could use it for. The 30a breaker protects the feeder and that is all that matters.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
volts is adequate for the circuits being supplied, it'll be fine. BTW you don't add up the amperage of the circuit breakers in the sub panel to determine the necessary feeder size for the panel

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
DesignGuy wrote:

A panel can run under it's rating but not over it's rating.
--
Blattus Slafaly ? 3 :) 7/8

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.