Overloaded lighting circuits...Why no phone call?

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Dark Sparky

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A warehouse facility was designed (on paper) using an incorrect lighting fixture wattage, that was only ~40% of the actual fixtures' wattage. This was 3 years ago and to the designer's knowledge, no issues have been reported by the facility Owner. For context, this is LED high-bay, 277V dry warehouse lighting. Also aside, there are no lighting controls/switches - they use the breakers at the panel to switch these lights.

The worst-case circuit - designed to be a 20A breaker - is 6832 VA, so vs. an 80% load of 4432 VA, it's 154% of the breaker's capacity. (Even vs. 100% of a 20A breaker, 5540VA, it's ~23% over.)

Thoughts on why this design issue (built 3 years ago) may not have been reported as causing any issues? Of course it's possible that the electrical contractor installed 30A breakers, or split the circuits if they noticed the potential issue. Obviously as responsible designer/EE, one has a moral/safety obligation to notify the Owner. But this is a bit gray when no issues are (apparently?) occurring. So this is both a moral and engineering question. Any relevant insight or suggestions are welcome.
 
Forgot - what's the worst-case that can happen electrically / safety-wise? Apparently the breakers aren't tripping, so they may be running very hot. There could be an issue if they electrical contractor installed larger (say 30A) breakers, but didn't upsize the wire.
 
The trip curves have a fairly large band of operation and are based on the breaker being in a 40°C ambient. If the ambient is lower, the amount of current required to trip the breaker goes up. A load that is 25% greater than the breaker rating is within the "never trip" part of the trip curve band on many breakers.
You need to look at the trip curve for your breaker and the actual ambient temperature that the breaker is operating in.
 
I agree with Retirede.

Do a site visit and see how the actual system is wired.
 
retirede said:
It sounds like you’re not certain it’s wired the way it was designed.
Verification of current state would be step 1.
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Agree. In addition to the "current state" of the wiring, measurements of the actual current draw in the various circuits would be helpful. ;)
 
don_resqcapt19 said:
The trip curves have a fairly large band of operation and are based on the breaker being in a 40°C ambient. If the ambient is lower, the amount of current required to trip the breaker goes up. A load that is 25% greater than the breaker rating is within the "never trip" part of the trip curve band on many breakers.
You need to look at the trip curve for your breaker and the actual ambient temperature that the breaker is operating in.
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Good advice, sir. I will see if we have trip curves...
 
ptonsparky said:
We haven't dealt with LED circuit overloads but did deal with HID circuits at full load back when. They often would last several years before the breakers started tripping.
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That's good to know. I suppose it should make me feel safe to know that we design to such safe standards (NEC) that frequently things are underloaded and less trigger-happy than we expect.
 
So bottom line - without knowing anything (I'll try, but may not happen) about what's actually installed - what should I do?

Let's assume (yes, I know what that means) that it was installed as-designed, overloaded on 20A breakers. Assume it's not tripping because the lights don't draw quite as much wattage as the manufacturer says. Also assume that the breaker's trip curves and cooler-than-max-temp-rating scenario mean that it's close to, but not tripping. In this likely scenario, do we have any safety concerns at all? Or simply the "inconvenience" that someday the breakers may start tripping?
 
jonathankpa said:
Good advice, sir. I will see if we have trip curves...
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Note that just because the breaker actually does carry the load, that does not make the installation code compliant.
I am just trying to point out that breakers do not have exact trip points and they may often carry loads greater than their rating forever.

The 80% rule is to avoid nuisance trips where the breakers are in a high ambient location and there are a number of heavily loaded breakers next to each other in the panel. In the breaker testing all breakers must carry their rated current forever in a 40°C ambient, but those tests are in open air and not in a panel where there is additional heat from other breakers.

I see no real safety concern here, assuming that the conductor size is matched to the breaker, as the current flow will not exceed the conductor's 90°C ampacity based on the numbers you have provided. The conductors and raceways will feel hot to the touch, but not hot enough to cause damage.

However there is a long term operational cost as the customer is paying for the electricity to heat the wires.
 
retirede said:
OK, I have to ask...being “states away”, how’d you get involved?
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If I were a contractor or electrician, that would be unusual to work out of state. But as an electrical engineer, I've designed many jobs that are states away. We simply have a long-distance relationship that means we designed this project in another state, and also have our professional engineering licenses in that state.
 
Terminator5047 said:
Or maybe they have lighting sensors and only certain zones are on at anytime thus limiting current. Chances are they pulled #10s for home runs and noticed and put it on 30s
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I understand that this project was built by a top notch elec sub. I think it's highly likely that you are correct, Terminator5047.
 
jonathankpa said:
If I were a contractor or electrician, that would be unusual to work out of state. But as an electrical engineer, I've designed many jobs that are states away. We simply have a long-distance relationship that means we designed this project in another state, and also have our professional engineering licenses in that state.
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Makes sense...thanks for satisfying my trivial curiosity!
 
Are there occupancy sensors on individual luminaires or groups of luminaires by any chance? If so maybe it never sees the full load for long enough to be a problem.
 
kwired said:
Are there occupancy sensors on individual luminaires or groups of luminaires by any chance? If so maybe it never sees the full load for long enough to be a problem.
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As far as we know, there are no controls and they simply use the panel's breakers to flip the lights on and off. But good point.
 
Terminator5047 said:
Or maybe they have lighting sensors and only certain zones are on at anytime thus limiting current. Chances are they pulled #10s for home runs and noticed and put it on 30s
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Can you put these luminaires on a 30 amp circuit? (see 210.23, in particular part (B))
 
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