I just installed a circuit of 14 105W CFLs, with only 11 actually screwed in. These bulbs draw .91 amps each. The breaker is a new 15 amp Square D using 12 gauge solid wiring in conduit. My amp meter shows a 9 amp draw with these 11 lights on. However there is a noticeable hum coming from the breaker. I've read other threads about this, but haven't found one that actually fixed the problem. Most comments in these threads said the circuit was overloaded, but like I said, I'm only at 9 amps. I'm going to try another new breaker tomorrow just to eliminate a bad breaker, but I'm not really anticipating any change. None of the other breakers hum in the box. So, what can I do? It will destroy the breaker eventually right?
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CFL and Circuit Breaker Hum
- Thread starter bfr57
- Start date
rockwithjason
Well-known member
Its probably harmonics from the cfl ballasts. A new breaker wont solve it and the hum will probably not damage anything.
ddawg16
Well-known member
The issue with CFL's is the duty cycle of the current. Unlike an incandescent bulb, the current load is not smooth....more like a big spike.
While your amp meter might be showing 9A...I'm willing to bet your peak current on each cycle is much greater than that. Your breaker is not tripping due to the 'averaging' it does with the loading. I'm guessing you are right on the ragged edge of it wanting to trip.
Basically, you are over loaded.
While your amp meter might be showing 9A...I'm willing to bet your peak current on each cycle is much greater than that. Your breaker is not tripping due to the 'averaging' it does with the loading. I'm guessing you are right on the ragged edge of it wanting to trip.
Basically, you are over loaded.
Redwolf947
Well-known member
Since you ran 12awg wire why not use a 20A breaker?
2Big2Ride
Well-known member
My 105W CFL bulbs are marked 1600mA on each bulb. I went with 9 bulbs on one 20A circuit and 6 bulbs, plus two ceiling fans on another 20A circuit. The circuit with 6 bulbs is quiet. The circuit with 9 bulbs buzzes ever so slightly with 6 bulbs on or all 9 bulbs on (2 switches). The 6 bulb circuit run is the furthest from the panel, the 9 bulb circuit is in the same area as the panel - don't know if that makes any difference. If your bulbs are like mine, 11 bulbs is too much for the circuit. ...assuming I correctly understand mA, A, and 80% of a 20A circuit.
wyliesdiesels
Well-known member
Oops, sorry, I used 14 for the lights and 12 for outlets........
So youve overloaded the circuit. Lighting is considered a continous load. And a circuit should not be ran at more than 80% for continous loads. For a 15a circuit that means no more than 12a and u have 14 bulbs running close to 1a each....