Fuse sizes

[KREW2]

I have just had a Quantum radar, and an Element 9 plotter installed. It has been working, but last Friday it did not power up. I checked the inline fuse and it had blown.
The recommended fuse is a 3 amp, but the electrician had put in a 2 amp.
My question is how crucial is fuse size? In this case the difference is 33% or 50% however you want to look at it.
With this discrepancy should I expect the fuse to blow, or is there possibly something more sinister.

 

[KREW2]

Just rechecked the spec. It should have been a 5 amp fuse not a 3 amp.
He probably mistook a 5 for a 2.

 

[jac]

The fuse is to protect the cable carrying the power - nothing else.

The device attached will have a certain power requirement so as a minimum the fuse must be large enough to carry that load but the cable should be even larger.

If it was a supplied cable then you're right the electrician maybe need to go to specsavers!

 

[Commercial Dave]

The cable should be sized according to the current draw requirement of the device, and the fuse should be sized according to the cable. The sole purpose of the fuse is to protect the cable from overcurrent faults.

I would check that the radar has been connected with sufficient cable. If it is advising a 5A fuse then I'd hope it has been wired with at least 0.75mm² cable. If the cable is more than a few metres long then ideally it should be at least 1mm². If the electrician has put in something much smaller and you replace the 2A fuse with a 5A one you may end up with a fire.

 

[KREW2]

The cable should be sized according to the current draw requirement of the device, and the fuse should be sized according to the cable. The sole purpose of the fuse is to protect the cable from overcurrent faults.

I would check that the radar has been connected with sufficient cable. If it is advising a 5A fuse then I'd hope it has been wired with at least 0.75mm² cable. If the cable is more than a few metres long then ideally it should be at least 1mm². If the electrician has put in something much smaller and you replace the 2A fuse with a 5A one you may end up with a fire.

Thanks but I think the rest is all fine. The radar is wireless and the power lead supplied and comes from the plotter.
I spoke to the electrician, they are a bonafide Raymarine agent, and installer.
When I told him he had only put a 2 amp inline fuse he was very apologetic, and as has been suggested maybe he should get his eyes checked as he must have mistaken the 2 for a 5.
Odd really as all spade fuses are colour coded, maybe he is colour blind as well. Still better that way than a 5 for a 2.