Fuse? Identification

[Diep]

New to us GB 42 with largely intact original wiring layout. Saw something I didn't understand and ran out of time to trace it out. I am assuming I am looking at a pair of fuses here.



I was initially concerned by the smaller conductors in contact with the fusible links which seems like a bad idea. It looks like I could break them out of the loom and easily re-route them.
Now that I am looking at the photo I am thinking more about the smaller conductors. This fuse certainly would not be protective of that wiring so I don't know if that is a bad idea to be feeding them off this fuse block.

I'm not at the boat but have the original wiring schematics. I thought this was DC but 3 and 4 look like the AC plug circuits. This element is not depicted in the schematic. Those circuits are already breaker protected. Blue/Black is original AC wiring scheme but red for AC + is unusual. It is strange that the blue/black wire color changes across the fuse. Obviously I need to keep digging to confirm what this is.

Main questions:
* Is this a fuse? What type? (I didn't see it in Calder)
* Should wires be moved out of contact
* Should this be updated to a newer style fuse and/or covered? (No, put it on a list, yes you're about to die)

Other thoughts?

 

[3rdOrderEffect]

Looks like current sense shunts to me.

 

[Diep]

Thank you 3OE!

Now that I know what I am looking at I can see these appears to be shunts on the P and S main engine alternators, feeding the ammeters at the helms.

 

[Duvie]

If I am not mistaken, those feeds to the ammeters should be fused! There is higher current there available than those small wires can support.

 

[Diep]

Interesting point. I can trace them and see if there is a fuse in the runs to the meters. I am guessing not as it isn't indicated on the schematic. Unless the meter itself provides protection a short on the sensing wires could see the full output of the alternator. If a fuse is added I wonder if it would spoil the meter calibration.

 

[Nick F]

Interesting point. I can trace them and see if there is a fuse in the runs to the meters. I am guessing not as it isn't indicated on the schematic. Unless the meter itself provides protection a short on the sensing wires could see the full output of the alternator. If a fuse is added I wonder if it would spoil the meter calibration.

1 the protection (fuse) should always be at the start of the thinner wire (because the wire is only protected downstream of the fuse). That is, there should be fuses immediately next the shunts in the thin wires going to the meter. There are "inline" fuses available. Personally I like the style in the link below.

Note: assuming the shunt is in the positive ("hot") line then fuses are needed in both wires.

2 the presence of fuses will have no effect whatsoever on the meter reading (the current going to the meter is very low).

Waterproof In-Line ATO/ATC Fuse holder - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

 

[Diep]

Great, we will look to add some fuses to the lines. While at it I suppose it would also be recommended to provide a shield of some sort to prevent accidental contact with the terminals or shunts.

 

[CharlieJ]

If I am not mistaken, those feeds to the ammeters should be fused! There is higher current there available than those small wires can support.

Not really. Your concept is spot on but the “higher current/wire size” comment is not. The sense wires carry milli or micro amps. They only sense voltage but they absolutely require fusing.1A inline glass fuses would be sufficient.

 

[Duvie]

Not really. Your concept is spot on but the “higher current/wire size” comment is not. The sense wires carry milli or micro amps. They only sense voltage but they absolutely require fusing.1A inline glass fuses would be sufficient.

Charlie, I probably wrote that poorly. My comment was to suggest that there is high current available from the Alternator wires at the shunt so the smaller wires need protection. As you mentioned current to the meters is very small but if a fault were to occur current would most likely be higher than the meter wires could handle.

 

[Papas]

While working on a significant electronics upgrade, I discovered that there were a # of places where GB had a higher AWG, unfused wire connected directly to significant current/amp sources (e.g. a 16 AWG windlass control switch wire connected directly to the 2/0 battery source post on the windlass breaker switch.). In my case, the 16G wire was completed toasted (see orange wire in below pic, and that was the least point of damage) along with damage to several other cables. This apparently occurred while under the "care" of one of the prior 3 owners, whoever it was, they were very lucky it didn't start a fire given the extent of damaged wires/cables. I just feel lucky to have found it prior to attempting to use the windlass!

Point is, I'd recommend all GB owners take a close look at high load items to confirm associated meters, control switches, etc. being feed from high amp sources, are properly fused!

 

[WillieC2]

Stellar crimp to boot.

 

[Rearmount]

I don't know where that is on your boat but that should be covered to prevent accidental high current discharge.

 

[Delta Riverat]

Yes, those are shunts, not fuses. I don't see any problems with the wiring and no need for fuses either.

 

[DDW]

If I am not mistaken, those feeds to the ammeters should be fused! There is higher current there available than those small wires can support.

Not really. Your concept is spot on but the “higher current/wire size” comment is not. The sense wires carry milli or micro amps. They only sense voltage but they absolutely require fusing.1A inline glass fuses would be sufficient.

Actually, Duvie is exactly right. It isn't the amount of current that a wire carries in normal operation, but the amount it might have to carry if there is a fault, that requires protection. If they were connected to something capable of only supplying milliamps, then no fuse would be required. But "there is higher current there available". Doesn't matter what the load normally uses.

 

[Diep]

Yep, agree. If the wiring shorted out somewhere along the route, the alts could melt those wires down.

Not super likely but the wire runs between the shunts and the meters are exposed and something could happen.

Adding fuses is on the list but hasn't happened yet. In the planning stages for an electrical upgrade and will make this and other safety improvements then.