Low Voltage to 12v water pump

[tree monkey]

10 minutes ago, catweasel said:

Not too bothered about kippers or celery myself, but Marmite! I love the stuff   A Marmite butty, using white bread with proper butter is one of life's luxuries to me.  My better half hates the stuff

A toasted crumpet with butter marmite and peanut butter, lush

[Kudzucraft]

Yea, I might have been a little rude, but I was just trying to fit in here.

 

Lets talk facts, not opinions.

As I have said repeatedly,  wire size determines what size fuse you need.

No one appears to have been on the boat, so no one knows what the wire size is.

Standards are great but you don't know if they were adhered too.

You don't know if someone has rewired it at some point.

Putting a larger fuse than was in there COULD lead to a fire.

So the Poster needs to determine what the wire size is to know what size breaker should be there

 

But I am just an ignorant American that couldn't possible know anything about British electricity.

 

[Guest]

Just now, tree monkey said:

A toasted crumpet with butter marmite and peanut butter, lush

Never tried both of those together. Always happy to experiment
Always enjoyed some crumpet though.

[WotEver]

7 minutes ago, Kudzucraft said:

wire size determines what size fuse you need.

On a narrowboat (which is long and thin, with correspondingly lengthy cable runs) cables are generally selected for voltage drop, not the smallest that can safely carry the current. This means that the fuse for that feed is not selected for the cable size because the cable used would be able to carry many times the current demanded by that circuit. 2.5mm would be the absolute minimum size for a water pump and I would expect a builder such as Liverpool Boats to have used at least 4mm if not 6mm. That is something which anyone with experience of narrowboats would be aware of, and why we are all confident that uprating the breaker to 15A when it’s feeding a circuit that is wired in cable that can comfortably handle well in excess of 30A will he perfectly safe. 

 

A knee-jerk reaction of NO doesn’t help the OP one iota. 

[Guest]

3 minutes ago, Kudzucraft said:

Yea, I might have been a little rude, but I was just trying to fit in here.

 

Lets talk facts, not opinions.

As I have said repeatedly,  wire size determines what size fuse you need.

No one appears to have been on the boat, so no one knows what the wire size is.

Standards are great but you don't know if they were adhered too.

You don't know if someone has rewired it at some point.

Putting a larger fuse than was in there COULD lead to a fire.

So the Poster needs to determine what the wire size is to know what size breaker should be there

 

But I am just an ignorant American that couldn't possible know anything about British electricity.

 

It is true that the protective device at the panel is intended to protect the cable and not the appliance. 

It is also true that an undersized breaker will cause problems due to nuisance tripping especially on anything involving a motor. I suspect that this has caused the problem for the OP.
To settle any futile arguments, as you allude, the OP would be wise asking somebody at a boatyard or similar sometime, whether the cable used is of sufficient csa for the 15A breaker.
It would need to be ridiculously small csa cable to need less than a 15A breaker,  and I would be very surprised if it was less than 2.5 mm sq for example, unless the pump was right next to the breaker, but one can never be 100% certain.  I feel that if the cables were so small as to need a 6 amp breaker, then other problems might have been encountered such as low pressure, or even refusal of the pump to run.
Owing to the length of most narrowboats, the builder's first consideration is volt drop, which usually demands cables with a csa that far exceed the necessary fuse rating (examples; my water pump is wired in 4.0mm sq cable and protected by a 15A type 2 mcb. I have seen 12V fridges with 16.0 sq mm cables, but again a much smaller breaker than the maximum cable capacity.)

[tree monkey]

1 hour ago, catweasel said:

Never tried both of those together. Always happy to experiment
Always enjoyed some crumpet though.

Always been a muffin man myself, not sure what that's says about me but there you go

[Guest]

1 hour ago, tree monkey said:

Always been a muffin man myself, not sure what that's says about me but there you go

LOL

[Alan de Enfield]

1 hour ago, tree monkey said:

Always been a muffin man myself, not sure what that's says about me but there you go

I was under the impression that Muffin the Mule was a sexual offence ?