I would like to start specifying an inline fuse for Metal Halide fixtures. I found some holders for midget class Bussman fuses but don't know what type of fuse should be used. The current project has Venture ballasts (150w PSMH, 120v) that specifies a 9 amp fuse... would that be a fast acting or time delay? What determines if the fuse will go before the breaker in a short circuit situation? When a ballast fails does it "all of a sudden short out" or does it's current draw gradually increase? Also, if anyone has any preferred holders they could recommend that would be great. Thanks
Ballast Fuse
- Thread starter cbq9911
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Most of the fixture manufacturers have an option to include an inline fuse.
I normally just specifiy those, and let the manufacturer worry about all the details like fuse holders, fuse ratings, and time delays.
I have seen some fixtures where the manufacturer gives options for both fast blow and slow blow fuses. I assume there must be some trade-off between nusiance blowing of fuses, and coordination with circuit breakers.
Steve
I normally just specifiy those, and let the manufacturer worry about all the details like fuse holders, fuse ratings, and time delays.
I have seen some fixtures where the manufacturer gives options for both fast blow and slow blow fuses. I assume there must be some trade-off between nusiance blowing of fuses, and coordination with circuit breakers.
Steve
I purchased some hazardous location fixtures recently and the option for the manufacturer to mount a fuse block with the fuse and prewire the block was $30. I purchased Bussmann GMF 5A time delay fuses and Bussmann HLR-2A fuse holders with 6" wire leads for a total cost of $4.40 per fixture. I can assure you the labor cost to wire nut the fuseholder to the ballast lead was much less than $25.60 each.
The failure mode that the fuse helps with is a short inside the ballast. I'm not sure how many ballasts fail this way, but it does happen and will keep the rest of the lights in the circuit operating when the one fixture failure occurs.
Your ballast should have a current inrush curve that you can overlay with the fuse curve to make sure that the inrush current won't blow the fuse. You can coordinate the luminaire fuse with the branch circuit protection the same way you coordinate any other overcurrent protection device. 5 amps worked for me, but if your ballast manufacturer is recommending 9 amps you may want to stick with that fuse rating.
The failure mode that the fuse helps with is a short inside the ballast. I'm not sure how many ballasts fail this way, but it does happen and will keep the rest of the lights in the circuit operating when the one fixture failure occurs.
Your ballast should have a current inrush curve that you can overlay with the fuse curve to make sure that the inrush current won't blow the fuse. You can coordinate the luminaire fuse with the branch circuit protection the same way you coordinate any other overcurrent protection device. 5 amps worked for me, but if your ballast manufacturer is recommending 9 amps you may want to stick with that fuse rating.
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