100% Rated Light Track Panelboard

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eeRyanC

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Location
Seattle, WA, USA
Hello,

I am an electrical designer working mainly on big box retail projects. As anyone who has worked with energy codes and big box retail knows, light track is one of the greatest challenges for energy code compliance - especially for stores that desire a grid-work of track through-out the space. Integral current limiters and remote current limiting panels help to make compliance possible, but due to the large amount of track I'm working with (roughly 5000' per floor), I'd prefer to use the branch circuit breakers (roughly 250' track per 1P/20A/120V circuit) as the current limiting device, therefore simplifying the system and reducing the number of home-runs. This method of track load compliance works great with all the major energy codes (Title 24, IECC), and for electrical service load calcs [due to 2011 NEC exception to 220.43(B)].

The only issue is that no-one seems to make a 100% rated panelboard with 100% rated 1P/20A branch breakers. I'd prefer 100% rated breakers to the typical 80% rated breakers since I don't have any control how many track heads my client is going to install on the track. I'd like to avoid a panel full of over-heating 80% rated breakers loaded at 90%. Any ideas?

I've considered installing a current limiting sub-panel with 16A breakers, but that is added cost, and if you check the fine print, those 16A breakers are really 80% rated as well so that's not a great solution. A fused branch panelboard may be 100% rated, but it would be a nightmare operationally speaking.

Thanks!
Ryan
 

eeRyanC

Member
Location
Seattle, WA, USA
Rob,

Thanks for the quick reply. As far as I'm aware, all available 15A panelboard breakers are still 80% rated and as such won't help in this case. For example, say I have 750' of track. No matter whether I break it out to (3) 20A circuits or (4) 15A circuits, breakers may still end up loaded at 90% of their rated load and over-heat.

Ryan
 

eeRyanC

Member
Location
Seattle, WA, USA
Thanks Jim. I hadn't taken the time to investigate 100% rated fused switches within an enclosure, but I'm not surprised that it would be similarly unavailable.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Interesting question. I would wonder how much heat will be generated at the panel if the breakers were loaded above 80% but all of the load conductors were over sized?
 
T

T.M.Haja Sahib

Guest
Looks like I'm stuck with using standard 80% rated breakers. Thanks anyway.

Ryan
Yes.Up to UL listed breakers of size 225A,the 80% rating holds............

So is it possible for you to consider a panel with breakers of above 225A capacity to serve your current purpose of 100% rated breakers ?
 
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eeRyanC

Member
Location
Seattle, WA, USA
Yes.Up to UL listed breakers of size 225A,the 80% rating holds............

So is it possible for you to consider a panel with breakers of above 225A capacity to serve your current purpose of 100% rated breakers ?
Good question. If energy codes permitted it, I'd serve my track panels on separate feeders back to a single 100% rated main breaker (and use that VA value for my installed energy). Unfortunately, the energy codes specifically allow you to use the branch circuit breaker but have no language that would allow use of an upstream main breaker for your installed energy.
 

eeRyanC

Member
Location
Seattle, WA, USA
Interesting question. I would wonder how much heat will be generated at the panel if the breakers were loaded above 80% but all of the load conductors were over sized?
I overlooked this post on my last read. I thought the same thing. I'll be over-sizing all the conductors anyway to minimize voltage drop (I want to get us much punch at the track-heads as possible).
 
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