Question about fuses

[Dougal]

Hi People

Couple of questions for the not quite so technically challenged as I....

We’re looking to make our boat as safe as we can, being as 3rd party only insurance is our only option.

I’ve seen fuses for sale, as being “suitable for alternators”. My understanding of alternators is that if fused, and said fuse blew, then goodbye alternator – is that not so????

We have a rather old and inefficient electric windlass that obviously should be fused in some way. The previous owner has fitted a domestic (230v) 100amp fuse breaker. Is this ok, or should we replace with a 12volt unit, or even a good old fashioned fuse? If I fit a fuse, what type should it be – there seems to be a myriad of different types, including quick or slow blow?

The whole ******* boat needs rewiring as much of it was obviously done with std automotive wire, and is now brittle. Ho, hum..... busy times ahead.

 

[VicMallows]

I have never heard a fuse described as 'SUITABLE FOR ALTERNATORS' and cannot imagine what they are trying to suggest.

It is not normal to have a fuse between between a 12v (or 24v) alternator and the battery, largely for the reason you suggest. Untimately you can argue there is some potential risk under certain fault conditions, but the fuse would need to be of such capacity that the trade-off is not worth it.

Without a full spec it is impossible to say, but generally any breaker intended for use on 230v mains will be designed for AC and will not be up to breaking a similar DC current. (the contacts will probably fuse together).

Vic

 

[pvb]

Fuses protect the wire - not the equipment. The biggest risk on a boat is that a wire connected to a battery shorts out, causing a huge current in the wire, and potentially starting a fire. To prevent this, wires should be fused as close to the battery as possible. Where thinner wires are used to feed individual bits of equipment, these should be appropriately fused, and this is typically done with a fused switch panel.

The main wire from alternator to battery should be fused. Yes, if the fuse were to blow it could damage the alternator, but a correctly-sized fuse shouldn't blow unless there's a fault somewhere. Without a fuse, a fault could cause a fire.

I use Mega Fuses on my boat. They are high quality, substantial fuses, with a slow-blow characteristic. I have one (200A) in the positive lead next to the starter battery, and a smaller one (100A I think) in the main positive lead next to the domestic bank. They are widely available from decent chandlers or online.

 

[Anonymous]

If your windlass breaker is working fine, then don't change it. There are differences in the contact material between ac and dc but for circuits that are seldom broken by the breaker itself there is no arcing and no wear. All of my Nauticat installed dc breakers are standard 230V ac breakers, no problem for most of the kit. However, the windlass is protected by a fuse, not a breaker. As I said, change it if and when it gives trouble unless the money is burning a hole in your pocket?

 

[Dougal]

"money is burning a hole in your pocket? "

Ha, ha.... I wish. Thanks for the feedback guys. Can anyone either reccommend or not, a company called Merlin Marine? They supply a good range of marine electrical equipment.