Ballast Inrush

[paul]

Anyone ever have problems with it?

I've got 53 fixtures on a circuit. All are the same and draw .23 amps at 277V. City requires that the circuit be fused at 20amps even though it's on a breaker. LCP controls 38 fixtures and wall switches and occupancy sensors control the other 15. The setup intermittently blows the 20amp fuse when the relay kicks on the 38 fixtures. When installing a 30amp fuse the system holds. I called the ballast manufacturer and they said that my inrush is 20-50X the operating current. That puts me at 175-450amps of inrush, depending on where the sine wave is when the 38 lights the are switched on.

Any thoughts on how to fix this problem?

 

[barbeer]

What type of luminaires are you dealing with? HID, Flour......

 

[paul]

2X4 flourescent trouffers. (2) T5 lamps per fixture. Ballast information is located at http://ultballastspecs.unvlt.com/ballastpdf/B228PUNV-C.pdf

 

[LarryFine]

I called the ballast manufacturer and they said that my inrush is 20-50X the operating current. That puts me at 175-450amps of inrush, depending on where the sine wave is when the 38 lights the are switched on.

Any thoughts on how to fix this problem?

I'd start by calling the manufacturer back and asking if they have an inrush current vs time curve available, and compare that to available fuse curves, if you want to do that much research.

You might also look into splitting up the load. Maybe leave 25 or so of the 38 fixtures on the existing controller, plus an added relay for the rest on a new circuit along with the 15 others.

 

[paul]

Right now, it's looking like option #2. At 450amps, it's way past the trip curve I have for the fuses. I'm not sure what the city is wanting by having these circuits on a fuse. If they are looking to help for a short circuit or ground fault protection than a 30AF would work just fine.

As of now, I'm looking at adding another fuse and ltg. another relay. Then splitting up the circuit before I hit the fuses. Bad thing is that this is a 20 story building and this floor is the first of the build-outs with the remaining 19 floors having the same setup. The EC doing the rest of the building is going to have fun.

 

[paul]

Here's the trip curve for the fuse. Bussman LP-CC-20

 

[keepitsimplestupid]

Say you broke it up into 3 parts or whatever the inrush current of the breaker can handle. So after the first part, put a time delay relay and a lighting contactor for the second 2/3 of the string. Make that delay as long as it takes the inrush to subside, then do the same thing again for the last third.

So the lights would come one say 1/3 of them at a time and a 0.5 second apart. www.ssac.com probably has suitable delay modules.

 

[paul]

I got an email back from the fixture company. They said, "Too many fixtures on a circuit for that size & type of fuse." So with that, I'm going to get another fuse holder and Wattstopper relay and split it in half, similar to the way Larry mentioned above.

Thanks for the input.

 

[weressl]

Anyone ever have problems with it?

I've got 53 fixtures on a circuit. All are the same and draw .23 amps at 277V. City requires that the circuit be fused at 20amps even though it's on a breaker. LCP controls 38 fixtures and wall switches and occupancy sensors control the other 15. The setup intermittently blows the 20amp fuse when the relay kicks on the 38 fixtures. When installing a 30amp fuse the system holds. I called the ballast manufacturer and they said that my inrush is 20-50X the operating current. That puts me at 175-450amps of inrush, depending on where the sine wave is when the 38 lights the are switched on.

Any thoughts on how to fix this problem?

Use a fuse with different T/C characteristics.

 

[cschmid]

I am curious here of what type of fixture because I was taught you added the ballast current to the bulb wattage to get the fixture draw..so lets say you have to 2 bulb 40 watt flourescent bulb fixture equal .29 + .23 = .52 x 53 = 27.56 you can correct me if I am wrong but that is to large of a load for a 20 amp circuit..

 

[LarryFine]

I am curious here of what type of fixture because I was taught you added the ballast current to the bulb wattage to get the fixture draw..so lets say you have to 2 bulb 40 watt flourescent bulb fixture equal .29 + .23 = .52 x 53 = 27.56 you can correct me if I am wrong but that is to large of a load for a 20 amp circuit..

Sorry, Charlie. The ballast label is supposed to show total current, including lamps.