I wasn't sure whether to ask this here or on https://electronics.stackexchange.com/ but this seemed the more appropriate place, please migrate it if not.
I'm in the UK and I've got a wall mounted connection unit (see picture below) with a 5 amp fuse in that leads to a socket outside and a lamp post in the garden.
The outside socket is used for plugging in a catering van to charge the battery, but also to use the sockets inside and power the 12v lighting when it's parked on the drive.
Now the fuse blows sometimes if you plug two things into the sockets in the van, but today I found it had blown sometime between last night and this morning (it was fine last night). When I went to change the fuse it blew the new one straight away. I had to unplug the van and remove the bulb from the outside lamppost before I could put a fresh fuse in and not have it blow.
I can still charge the van (which is the main use for the socket outside) but it would be nice not to have to worry about it.
So my question is, can I put a 13 amp fuse in the unit instead of a 5 amp one? Will this cause any problems (like short circuiting the houses fuse box instead of merely blowing the fuse in the unit) or be dangerous?
Best Answer
In general, NO. Replacing a fuse with a higher-amp fuse is a very bad idea and can lead to fires.
Fuses (and circuit breakers) are rated such that they blow or trip before any part of the circuit gets to a dangerous current. You rate the fuse or breaker based on the lowest current rating of all the devices and wires in the circuit .
In your case, the manufacturer of the connection unit determined (somehow) that the "weakest link" in that circuit can only draw 5A before it exceeds its limits. Putting in a 13A fuse would thus allow that weakest link to draw almost 3 times what it may be designed to, which leads to increased heat and then fires.
There is a reason your fuse is tripping and you need to figure out what that reason is. Perhaps there is a problem with your lamp post, the bulb, one of the sockets, or the van charger. Fix the underlying problem, and you won't have any more blown fuses.