Which fuse for pond pump?

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My pump stopped working today and I can't figure out the issue so I've ordered another (All Pond Solutions Aqua Eco).
I removed the power cable from my outside junction box today so I could wire it to a household plug and try it on the mains. It worked until I turned it off again...
Anyway, I noticed that in my junction box where I only have the pump and the UV wired in (other two sockets wires to old equipment), that the pump was wired to the 5amp socket/fuse and the UV to the 3.15amp. In their manuals they both say they should be fused at 3amps.
My question is, am I ok to wire up the new pump when it comes to the 5amp, even though it says 3 in the manual? The last one was running for around 2 years on the 5, so does it make all that much difference? I can't actually find any junction boxes that have 2x3amps....
Any help is greatly appreciated.
From left to right in image, pump, UV, not in use, not in use.
 

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The fuse is to protect the cable. Cable so small that it needs a 3a fuse is not allowed. As is often the case the manual is not really correct.
 
My question is, am I ok to wire up the new pump when it comes to the 5amp, even though it says 3 in the manual? The last one was running for around 2 years on the 5, so does it make all that much difference? I can't actually find any junction boxes that have 2x3amps....
Unlikely it would make any difference.

However the 5A fuse could easily be changed to a 3A one, all of the fuses in that unit are the same physical size.
 
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Unlikely it would make any difference.

However the 5A fuse could easily be changed to a 3A one, all of the fuses in that unit are the same physical size.

Well 3A in that size not available, the nearest would be 3.15A. But the board is labelled 5A. Perhaps the designers of the PCB know about motor start up surge. Perhaps the person that wrote the manual thought he knew better even though he did not know that fuses in that size come in 3.15A not 3A.
 
I can't read the spec on the fuse, and fuses of that size come in different flavours, fast blow, slow blow, semi-conductor not simply 2.5A 3.15A and 5A. It could be simply to protect cable, but unlikely as all those cables would take well over the fuse size, so there are two reasons, one is to protect what it supplies and the other is to maintain supply to other items if one item goes faulty, so fuse blowing in the junction box stops main supply fuse blowing.

Fuses do degrade over time, and normally you would replace one like for like when they blow, but if that one blows, then clearly a fault. However replacing a fast blow fuse for a standard BS1362 found in a 13A plug may not offer the same protection. We see bathroom extractor fans fitted with a 1A BS1362 fuse and the fuse wire inside is thicker than the windings for the fan, so if the fan stalls the fan still burns out, the fuse does not protect it.

We have all had the box of fuses
FF03040-40.jpg
and got the one which "looks" right, and we have all latter realised there was a little more involved, however 3.15 is close enough to 3 not to worry, and if the manufacturer says 5 amp then fit 5 amp, you have the data sheet not us.
 

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