When is a 30A fuse not a 30A fuse?

[JumbleDuck]

Yes Len, totally agree with that. Fuse from distribution board chosen to suit cable size, then subsequent fuses (which I would always fit) chosen primarily for the individual or group of equipment they are feeding.

My boat is wired for incandescent lights inside which, since the lights on each side are in parallel, means it was designed for 6A/4A/2A. Now I have LED bulbs everywhere, so the currents should be a fraction of what they were. Fusing each light fitting isn't practical, and I certainly don't want any LED bulb drawing 10A without something noticing.

 

[rogerthebodger]

My boat is wired for incandescent lights inside which, since the lights on each side are in parallel, means it was designed for 6A/4A/2A. Now I have LED bulbs everywhere, so the currents should be a fraction of what they were. Fusing each light fitting isn't practical, and I certainly don't want any LED bulb drawing 10A without something noticing.

What is being said here is correct about fusing to device load current loading but as JumbleDuck with LED lighting it's just not practical. I have doing on for 50 separate LED lights and I separated then into 3 zones each with their own circuit breaker but this breaker is/must be rated for the total load that is much greater the the current rating for each LED light and is own wiring.

What do the experts say we should do in the case.

 

[DickieT]

My boat is wired for incandescent lights inside which, since the lights on each side are in parallel, means it was designed for 6A/4A/2A. Now I have LED bulbs everywhere, so the currents should be a fraction of what they were. Fusing each light fitting isn't practical, and I certainly don't want any LED bulb drawing 10A without something noticing.

Much as I do not like add on in line fuses, I would simply add an in line fuse after any, now, over current rated breakers to bring the fuse rating down to an acceptable level. ATO blade fuses are available down to 1A or if you want to go really low olde worlde 1.25" cartridge fuses are available down to 60mA or so ! However in practice I would not go lower than say half an amp, mechanical rigidity might become a problem. Good in line sealed holders are available for ATO fuses. I would not consider individual fuses per light, group them. Personally I would add say a 1A in line fuse. It will go pop before any damage is done if a LED goes short.

 

[Len Ingalls]

My boat is wired for incandescent lights inside which, since the lights on each side are in parallel, means it was designed for 6A/4A/2A. Now I have LED bulbs everywhere, so the currents should be a fraction of what they were. Fusing each light fitting isn't practical, and I certainly don't want any LED bulb drawing 10A without something noticing.

Then,you have a good PRACTICAL reason to reduce the fuse size at the panel/switch in this case. Nothing wrong or unsafe to fuse a distribution cable at lower than the cable's maximum rated ampacity.

 

[nigelmercier]

... the fuse is there for overload protection of the cable AND the device it is supplying...

Exactly. See numerous other threads where the "cable protection" myth has been corrected.

 

[Martin_J]

Just an update to say thanks for all the input last year.

In the end I did go for the Midi fuses from Furneaux Riddall and they have been in and working for the past year. Solar and wind inputs both still working although I was surprised that the solar did produce more power than the wind.

Thanks.