As some of you know from chat, I had to troubleshoot a string of pole lights that tripped the breaker due to one shorted ballast. Lots of shoe leather.

I have heard some people put fuses in the pole bases. Sounds good to me. Does anyone have any suggestions as to what type/class of fuse? Fast acting or time delay? And how to size? The current set up is 480 volt 1000w HPS fixtures. They are fed by a 20 amp double pole breaker.

Also I notice that bussmann makes "breakaway" holders for pole lights, at least that what their catalog says. Not sure what "breakaway" means exactly does anyone know?

My concern is of course coordination. This will not help if the breaker trips before the fuse.

1k HPS ballast is 2.3 amps, & I can't remember if operating or starting current is higher.

Some locations have midget fuses in in-line fuse holders at the base; one set of poles has a fuse block (finger safe, Bussman) in the base.

My guess 3 amp, time delay.

A good place to get great info is Bussman.com; drop an e-mail to one of the fuseoligists.

John

I think I would start with FRN 5s. That is over double the running amps so nuisance popping shouldn't be a problem but one shorted ballast would still not overcome the breaker (16a per 20 design load)

BTW they also make indicating fuses/holders to really make troubleshooting easy.

I would guess that 'breakaway' refers to something that would unplug when the pole is knocked over.

I think the Bussman in-line fuseholders I've been using are called "HEG." They use fuses such as KTK (fast acting) and FNQ (time delay).

I strongly recommend using time-delay type fuses, especially with HID lights.

The one drawback to the fuseholders is that it is difficult to get a good crimp. If the fixtures are not already wired with stranded wire, I suggest re-wiring them - or at least make pigtails.

Many lighting companies install inline fuses for customers as part of the service. A 1000w 480vac fixture only needs a 4 or 5 amp fuse. The installation of fuse really helps the troubleshooting, if all the lights are parallel then fuses that control each pole blows when that light has a problem.