Sizing fuses for ballasts

[mark32]

I'd like to start installing inline fuses when I replace caps and ballasts on HID fixtures. How does one figure the fuse size?

 

[jdsmith]

The ballast manufacturer should provide an inrush current curve. The key is that the trip curve of the fuse be lower than the trip curve of the branch circuit so the fuse blows and you achieve what you were trying to achieve for the $10/fixture expenditure. The application I was looking at was 165W induction lamps fed from a 20A, 120v branch circuit. A class CC time delay fuse of about 3 amps works for me in that the inrush wouldn't blow it and it would always blow before the breaker would trip. I haven't looked at ballast inrush, but I would guess something similar would work for you.

 

[iwire]

I'd like to start installing inline fuses when I replace caps and ballasts on HID fixtures. How does one figure the fuse size?

Go to http://www.advancetransformer.com/

I have found the info there, I did it by looking up specific ballast sizes and looking at the spec sheets.

For example a 1000 watt MH running at 480 volts takes a 5 amp class CC fuse.


By the way, if the fixture is wired line to line install a fuse in each line so a ballast short does not drop out the entire circuit.

 

[mark32]

Thanks guys for the tips and the link. I'm glad to have found such info on the Advanced site, wonder why they don't give you these specs along with the ballast?