I'm planning to eventually buy some inline fuses for use in all of my magnetically ballasted fixtures.

What is the best fuse rating for 2xF40 full power ballasts, as well as 1xF40 and 2xF32?
Where I can buy good quality inline fuses/holders in bulk?
Can I use automotive ones with the 2 prong fuses?

Would also like to get some ballast quick connectors as well, like the ones that came with some of my Lithonia turrets. A little plug thing that goes on the ballast leads and allows to safely and quickly "unplug" a ballast from the line.

I've tried to search for these items but cant seem to find anything that's not questionable quality or comes in larger quantities for the price. Would like 100 of both connecters and inline fuses.

I'm not in any hurry so i have plenty of time to take in leads or suggestions.

Thanks!

I don't know about specific ratings or sources for fuses and fuseholders, but automotive fuses / fuseholders are NOT suitable for mains voltage.

Overall I think this is a good idea, I would look on Ebay for a bunch of assorted size fuses.

An electronic components distributor such as Digikey or Mouser will have what you're looking for and will generally offer price breaks if ordered in large quantities.

I generally use 1/4" glass fuses but the 5x20 fuses work as well.

Automotive fuses aren't suitable for use on AC circuits, they're typically rated for DC only with a maximum voltage of 32v or 48v.

Most of my fixtures are fused at 1A.

Agree with recommendation of going to a reputable electronic distributor. I am not 100% sure about American practice, but fuse time rating is important, too. With fast blowing fuses you are at risk the fuse will blow at transients when power is turned on, so slow-blow ones probably are a way to go. Ceramic fuses are slightly more expensive but are of better quality and do not annoyingly crack when they blow.

You need to calculate fuse value for each luminaire taking power and power factor into account and then adding some safety factor of say, 1.5X. 1A rating may appear too low with larger fixtures at 120V and inefficient magnetic ballasts.

In 230V world we never fuse individual fixtures, but with mostly single choke ballasts the risk of dangerous short is very low.

And do not ever attempt to use automotive fuses. They may fail to interrupt the arc with the consequences!

1A seems to work well enough for typical 2x F40T12 HPF rapid start ballasts with have a rated draw of 0.73A to 0.80A depending on model. It's around 1.25x the current rating.

For the lower wattage fixtures, I generally fuse at 1A as well for simplicity but you can also buy fuses rated for 500mA, 600mA, or 750mA. I generally only fuse fixtures with 40w preheat ballasts, rapid/trigger start ballasts. I generally don't fuse fixtures with choke ballasts or electronic ballasts.

For the higher power fixtures such as 8ft fixtures and HO/VHO fixtures you'll have to size them based on the current rating on the ballast for that given lamp type using what RRK suggested.'

As for the orange ballast plugs, they are known as ballast or luminaire disconnects and you can get small quantities from Home Depot.

I also like using the inline Wago connectors for ballast quick connects. You can also order them from Digikey or Mouser in large quantities for cheaper as well.

I saved the link for the ballast connector, thanks RRK!

I love using the wago connectors for all my fluorescent. It makes ballast swaps and setups really quick and no wire damage like from twisting.

I checked mouser and they seem to be very expensive, like $50 or more for a single unit, and their search isn't all that helpful.

Noted, do not use automotive fuses.

Just want to get something in bulk for a realistic price thats similar to the one pictured or better

Had to severely crop attached photo, because apparently 2Kb is all thats allowed, which is very hard to accommodate in 2025 when every phone takes multi MB pictures by default.

I've had a look at digikey and found what looks to be suitable for my needs, ill paste the links.

Fuseholder: https://www.digikey.ca/en/products/detail/littelfuse-inc/01500332H/3425489

Fuse 1a slow blow: https://www.digikey.ca/en/products/detail/bel-fuse-inc/3SB-1-R/1009830

Fuse 1.5a slow blow: https://www.digikey.ca/en/products/detail/eaton-electronics-division/BK-MDL-1-1-2-R/954317


I intend to use the 1A on single lamp F40 ballasts. The 1.5A for 2 lamp ballasts.

Looks like you found some decent choices, the fuseholder datasheet even listed protection of lighting ballasts as one application. The nice thing about buying from Digikey is that they'll offer price breaks so if you need a lot, it's often better to buy large lot. They will also sell individually too.

For sure, and yeah I noticed they had good discounts for the quantity, and itll be a breeze to set up in fixtures with the wagos.

I’ve never seen any fluorescent ballast with a fuse inside the fixture. I’d suggest mounting them so that they are easily accessible, because one overvoltage or undervoltage condition and the fuse may pop even though there’s nothing actually wrong with the ballasts. I don’t think I’ve ever ran across any fixture with fuses aside from reset starters of course. might be a nice idea for preventing the room from being filled with smoke if you’re running very old ballasts and one suddenly gives up. magnetically ballasted fixtures rarely fail though. However I wouldn’t be worried with newer ballasts , I’ve never had one fail. The worst thing that has happened is the ballast went open circuit.


Here in Europe there are no fluorescent fixtures that are fused individually, they usually all hang off of C10 breakers, sometimes C16 if it’s a larger installation. 15 fixtures per 10 amp breaker is usually not a problem. Three phase load splitting is also very common and always makes me happy to see it



Buy proper fuses and fuse holders from real electronics suppliers. 5x25mm fuses should do fine for your application, I’d try a T1A, if that blows try a 1.5. Don’t bother with fast blow, they’ll almost surely blow immediately if your fixture has a phase compensation capacitor as the current flowing in and out of the capacitor will be quite high before the tubes strike up and it starts doing its job. Yes I know it sounds weird but that’s how it works hard to explain over text!

For the fuses use only the ceramic ones. The glass ones have breaking capability at 250V only 20A, not suitable for mains circuits at all. When the fault currents happen to be above that and below the short circuit tripping point of the upstream breaker, this fuse could become fire safety problem on its own.
The ceramic ones have breaking capability 1.5kA, which is really bare minimum for a fuse behind main breaker (the ranges of the breaker short circuit trigger and the fault currents this fuse is able to break safely do overlap in a sufficient manner).

And because of their tolerance and required margin (to not blow on good ballasts), I doubt the fuse will be able to prevent severe ballast overheating if the ballast really fails that way.

Thank you for mentioning that you’re right, only use the ceramic ones for mains voltage. Even those are a little on the weak side but generally okay as long as you have a proper breaker or fuse before the load, which I’m sure you do if your building has been wired properly

Buy proper fuses and fuse holders from real electronics suppliers.

I thought digikey was a real electronics supplier? Joseph_125 pointed out for me it even listed ballast protection in its datasheet.

For the fuses use only the ceramic ones. The glass ones have breaking capability at 250V only 20A, not suitable for mains circuits at all.

I selected the 250v 1.5A and 1A rated fuses, which are glass slow blow type.



My goal isn't to compensate for the mains breaker or wiring. I want to add an inline fuse to each ballast individually. The majority of my ballasts are Philips/Advance from around the Kool koil era, which are good performers but can fail by internal shorting.

Years ago, an older gentleman who's house i was checking up on daily by request while he was on holiday, one of his shop fixtures ballast failed, and the ballast was cycling its thermal protection every 10 seconds, causing other lights to dim everytime it reconmected. It also made a noisy buzzing each cycle. It had popped all 4 filaments in the 2 F40s. I shut it off and made note for him, and upon his return, I sold him a replacement ballast and installed it for him. The bad ballast was a Philips Kool koil. Had it been fused individually, it would have disconnected as soon as it began pulling abnormal current. Thankfully its inbuilt protection stopped it from being a smoke show.

He never turned off his lights so these had some serious hours.

Id like to have all my future fixtures equipped with individual fuses so if anything should go wrong in one, it will cut off before it can risk any serious damage or smoke.

My plan is to use 1A fuses for single lamp, and 1.5A for two lamp. On HPF ballasts only. I think if the caps fail and it becomes LPF, it will also pop the fuse.

DigiKey is pretty trustworthy for electronic components and is a authorized distributor for the parts they list. Just make sure you're buying from them and not a DigiKey Marketplace seller.

Individual fusing of fluorescent fixtures was a option available from the factory for most fluorescent fixtures here. Either internally mounted or mounted in a externally accessible panel mounted fuseholder. Some building owners specified individual fusing for their fluorescent luminaires.

The same was a option available for most HID luminaires as well, even cobraheads.   

Interesting! And smart, honestly! Prevents a potential fire should something go wrong

Maybe not such a bad idea to implement on my 1944 vintage fixture in my workshop!