Can "too many" LED fixtures on a circuit trip the breaker?

R

Ragin Cajun

Senior Member
Location
Upstate S.C.
Some years back I recall incidents where LED's tripped the circuit breaker if there were "too many" on a circuit.
Is this still true?
Low many LED's can we really put on a circuit?
Is there any "standard", rule of thumb, or any way of knowing?
I know that supposedly LED have a big "inrush".
In the "old" days we could load up a circuit with fluorescent fixtures to 75% without any issues.
How much can we "safely" load up a circuit with LED fixtures? I would like to take advantage of loading up several circuits instead of having to spread them out over many circuits.

Thanks
RC
 
Most modern LED fixtures have a driver. If you know the driver current you can calculate how many can be on a circuit.
 
I believe the op’s question is if high inrush is still a problem with LED drivers? Depends on the breaker, Square D QO and QOB is more sensitive to inrush than say, GE (now ABB).
 
Here's some specs from the HALO RL4, just the first fixture listed in the catalog I downloaded from them:

Input Voltage: 120V
Input Current: 0.069A
Input Watts: 8W
Inrush: 2.3A
THD <= 20%
PF >= 0.90

Looking some of the other fixtures, that's a particularly poor Inrush / Input Current ratio; for example RSQ6 says

Input Current: 82 mA
Input Watts: 9.8W
Inrush(A): 0.69 @ 14 ms.

Anyway, if you just look at the Input Current of 69 mA, even if you consider them a continuous load, you could put 173 RL4 on a 15A circuit. But with an inrush of 2.3A, presumably that would not work, if they are all switched together (which can happen even if they are controlled in smaller groups, say after a power failure when all the fixtures were previously on).

So to rephrase the OP, if you have an Inrush current figure on your LED fixtures, how do you determine the inrush limit on the number of fixtures you can put on a given rating branch circuit? Is there a rule of thumb like "inrush should not exceed 5x the breaker rating"?

Cheers, Wayne
 
Tungsten incandescent lamps also have a high inrush current, and our entire electrical system was designed around them. LEDs are probably OK as long as the continuous current is accounted for properly.
 
Incandescent lamps have roughly 10x inrush.

@wwhitney posted specs for two different fixtures, with 33x and 8x inrush.

So I think the answer for the OP is that it depends on the specific fixtures.

For a multi volt fixture, I'd expect higher inrush and lower operating current at higher voltage
 
CoolWill said:
Tungsten incandescent lamps also have a high inrush current, and our entire electrical system was designed around them. LEDs are probably OK as long as the continuous current is accounted for properly.
Click to expand...
We had a Target cosmetics rollout, that the display lights were cheap led, and were high inrush. Target used Square D QOB breakers in a lot of the stores. We were only able to load the circuits to four to five amps per circuit due to inrush.
 
The Qwick Open feature of QO 1 pole 15A and 20A is 10X for 1 cycle. For other breaker it is roughly 10X for 3 cycles.
 
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It entirely depends on the topology of LED ballasts in question.

Many A19 screw-in bulbs these days often have a 10 ohm resistor in series at the input, however CFLs and older screw-in lamps as well as some LED ballasts have a very high inrush. The theoretical inrush in absolute worst case (at the terminal of 10,000kVA transformer and turned on at peak crossing) of such bulbs would be 17A per lamp.

Some CFLs actually even came with a warning like not to exceed 12 or 20 per 15A circuit in order to prevent a magnetic trip.

This is something you can check using the "fast peak" function on many Fluke meters. Power up, power off wait a 5-10 seconds and repeat a few times. Some will only draw an amp or two. Some will draw as much as 30A. High inrush is undesirable especially in frequently cycled applications as it's very destructive to contacts.
 
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Thanks for the replies!
JMHO, such high inrush values indicate a terrible design.
Depending on the magnitude of the LED inrush, we could need many more circuits for a given area with LED's vs , say fluorescent fixtures?
Seems we have gone backwards in needing more circuits, thus more breakers, more wiring, etc.
Why weren't the LED drivers designed to minimize the inrush. Looks like the cheap road was taken!
I don't have any fancy inrush reading meters, so if looks like I need to depend on the vendor's data, it you can trust that!
RC
 
hillbilly1 said:
I believe the op’s question is if high inrush is still a problem with LED drivers? Depends on the breaker, Square D QO and QOB is more sensitive to inrush than say, GE (now ABB).
Click to expand...
QO has lower magnetic trip for standard 15 and 20 amp single pole breakers. They do have 15 and 20 amp breakers with a -HM suffix (for high magnetic) that have same magnetic trip as 15 and 20 amp two and three pole breakers. I mostly have used them for when there is a motor load that won't start without tripping the breaker.

I have no idea what the magnetic trip is for GFCI, AFCI or dual function QO 15 and 20 amp single pole breakers. Have not really had issues with those so maybe they don't have the lower magnetic trip setting?

I think they also have the lower magnetic trip on standard 15 and 20 amp single pole breakers in the Homeline series as well as a -HM breaker for when you do have the need for a higher magnetic trip setting. Almost never need that in a dwelling so have not had to use those as often but seem to recall they do have them. I seldom use Homeline for anything but dwellings.
 
kwired said:
QO has lower magnetic trip for standard 15 and 20 amp single pole breakers. They do have 15 and 20 amp breakers with a -HM suffix (for high magnetic) that have same magnetic trip as 15 and 20 amp two and three pole breakers. I mostly have used them for when there is a motor load that won't start without tripping the breaker.

I have no idea what the magnetic trip is for GFCI, AFCI or dual function QO 15 and 20 amp single pole breakers. Have not really had issues with those so maybe they don't have the lower magnetic trip setting?

I think they also have the lower magnetic trip on standard 15 and 20 amp single pole breakers in the Homeline series as well as a -HM breaker for when you do have the need for a higher magnetic trip setting. Almost never need that in a dwelling so have not had to use those as often but seem to recall they do have them. I seldom use Homeline for anything but dwellings.
Click to expand...
I’ve only had to use the HM breaker on a hydraulic pump. For some reason it would run on an extension cord, but not on the receptacle below panel. Apparently the extension cord reduced the startup current, or acted as a choke.
 
hillbilly1 said:
We had a Target cosmetics rollout, that the display lights were cheap led, and were high inrush. Target used Square D QOB breakers in a lot of the stores. We were only able to load the circuits to four to five amps per circuit due to inrush.
Click to expand...
That's crazy. I guess it's the capacitance in the drivers that has such an inrush?
 
Unfortunately, the fixtures I am using don't list inrush current. @#$%&* Just great!
Thanks for the info on the SquareD high inrush breakers.
I haven't had the inrush problem - YET. But the two apartment buildings I am working on now may be an issue.

RC
 
Just thinking out loud here, should we not be obeying the NEC codes as to how many lamps we can put on a circuit breaker and wire size and VA rating per lamp?
 
a.bisnath said:
Just thinking out loud here, should we not be obeying the NEC codes as to how many lamps we can put on a circuit breaker and wire size and VA rating per lamp?
Click to expand...

The issue is that the lamp VA rating is quite low, but the inrush VA might be quite high. This leads to a seemingly properly sized circuit that will trip the breaker if all the lamps on the circuit start at the same time.

I wonder if some sort of time delay relay could work to divide the circuits. Flip the breaker and half the lights turn on immediately, half in a second.

Jonathan
 
Flicker Index said:
It entirely depends on the topology of LED ballasts in question.

Many A19 screw-in bulbs these days often have a 10 ohm resistor in series at the input, however CFLs and older screw-in lamps as well as some LED ballasts have a very high inrush. The theoretical inrush in absolute worst case (at the terminal of 10,000kVA transformer and turned on at peak crossing) of such bulbs would be 17A per lamp.

Some CFLs actually even came with a warning like not to exceed 12 or 20 per 15A circuit in order to prevent a magnetic trip.

This is something you can check using the "fast peak" function on many Fluke meters. Power up, power off wait a 5-10 seconds and repeat a few times. Some will only draw an amp or two. Some will draw as much as 30A. High inrush is undesirable especially in frequently cycled applications as it's very destructive to contacts.
Click to expand...
But most homes use inverse time breakers with possible trip delay. Would the inrush cutrent time often exceed this delay?
 
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