Add-A-Circuit/ Fuse question

I'm installing PIAA 510's in my fog locations and some Wal-Mart Burners in the cubby's for bed lights. I picked up two add-a-fuses to tap into two slots that are only powered when the ignition is on. They will be for the power to the new switches and their illumination. Here's my question:
I know the fuse in the first slot on the add-a-fuse will be the original size as the location I'm tapping into, but what size fuse should be used for the power to the switches and the illumination of those switches??

 

By power to the switches, are you talking about the power circuit to activate the relay? If so, a 2A fuse should be more than enough. It's what I have used to activate two relays.

 

Yes. it's to power the circuit to activate the relays. I knew it would be a small amp fuse as it's just powering the relay and illuminating the switch LED, but I didn't think it would be as low as that. So, If I have 5A fuses lying around, then I guess I'm good to go....

 

I'd go below 5A if you can, just to be safe. 3A fuses are pretty easy to come by. 2A is a little harder, but I found a stash of them so that's what I use.

 

+1

The important thing to remember is that the primary job of the fuse is not to protect the items connected to power. The job of the fuse is to protect the wiring from the power source to the accessory.
If the wiring is rated for 10a, then use an 8a fuse. Never use a fuse that is more than 80% of the design spec for the circuit.
Installing a larger fuse because one blows is stupid and asking for a fire.

But given adequate wiring size, always use the smallest fuse that will support the item being powered. Again, the 80% rule applies... if the item draws 4 amps, then do not use a fuse smaller than 5a.

So actual load < 80% of fuse rating
Fuse rating < 80% of wire gauge limit

4amps would be about 55 watts to give an idea. A motorcycle headlight circuit is normally a 10a fuse.

Capacities:

24 = 3.5a = 2.8a fuse = 2.24a load continuous
22 = 7a = 5.6a fuse = 4.48a load
20 = 11a = 8.8a fuse = 7.04a load
18 = 16a = 12.8a fuse = 10.24a load continuous
16 = 22a = 17.6a fuse = 14.08a load continuous
14 = 32a = 25.6a fuse = 20.48a load continuous
12 = 41a = 32.8a fuse = 26.24a load continuous
10 = 55a = 44a fuse = 35.2a load continuous
8 = 73a = 58.4a fuse = 46.72a load continuous
6 = 101a = 80.8a fuse = 64.64a load continuous
4 = 135a = 108a fuse = 86.4a load continuous

 

I found the 2A fuses sold loose at the local hardware store - everything works perfectly.