Hi everyone.
I am re-wiring my CD-36. The original wiring was really bad. The insulation was cracking off in spots, the area behind the electrical panel was a true rats nest of tangled wires, and many of the wires were under sized. If you read my response to Stuarts message below you can see that I did enough homework to know that the ABYC does not require the use of fuses between the battery and starter motor. That said, it still seems like a good idea. I have a 100 amp breaker protecting my main distribution panel so the fuse just needs to protect the battery cables. I can not seem to get the information that I need on what size fuse should be used with a Perkins 4.108 engine. I imagine that it must be somewhere below 200 amps, since the original battery cables were number 4s. Anyone out there with a CD-36 had fuses installed? Had problems?
Matt
mcawthor@bellatlantic.net
Battery Fuse size for Perkins 4.108
Moderator: Jim Walsh
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Larry DeMers
Re: Battery Fuse size for Perkins 4.108
Matt,
This is not something I would do myself. The inrush current of a normal starter can be enormous..1000 amps for a short period of time, so the fuse needs to be a time-delayed fuse, sized for approximately 150% of the largest load likely to be seen. That said, suppose you are trying to boogie out of an anchorage at oh-darn-early in the AM, you need the engine to start and on this occasion, the alternator acts up, dragging the rotor a bit, or the engine takes a bit of coaxing to get going, pulling more current than you normally do. Pop goes the fuse, and now you cannot start that beast.
I would put in a catestrophic failure protection for hte wire..not the starter, making the fuse 750A or better, depending on wire gauge.
ABYC standards do _suggest_ (they cannot require it, legally) a fuseable link for every battery, **mounted within 7 inches of the battery**. This will protect all cabling going off battery. Generally the size is in the many 100's of amps.
Cheers,
Larry DeMers
s/v DeLaMer
CD30
demers@sgi.com
This is not something I would do myself. The inrush current of a normal starter can be enormous..1000 amps for a short period of time, so the fuse needs to be a time-delayed fuse, sized for approximately 150% of the largest load likely to be seen. That said, suppose you are trying to boogie out of an anchorage at oh-darn-early in the AM, you need the engine to start and on this occasion, the alternator acts up, dragging the rotor a bit, or the engine takes a bit of coaxing to get going, pulling more current than you normally do. Pop goes the fuse, and now you cannot start that beast.
I would put in a catestrophic failure protection for hte wire..not the starter, making the fuse 750A or better, depending on wire gauge.
ABYC standards do _suggest_ (they cannot require it, legally) a fuseable link for every battery, **mounted within 7 inches of the battery**. This will protect all cabling going off battery. Generally the size is in the many 100's of amps.
Cheers,
Larry DeMers
s/v DeLaMer
CD30
matt cawthorne wrote: Hi everyone.
I am re-wiring my CD-36. The original wiring was really bad. The insulation was cracking off in spots, the area behind the electrical panel was a true rats nest of tangled wires, and many of the wires were under sized. If you read my response to Stuarts message below you can see that I did enough homework to know that the ABYC does not require the use of fuses between the battery and starter motor. That said, it still seems like a good idea. I have a 100 amp breaker protecting my main distribution panel so the fuse just needs to protect the battery cables. I can not seem to get the information that I need on what size fuse should be used with a Perkins 4.108 engine. I imagine that it must be somewhere below 200 amps, since the original battery cables were number 4s. Anyone out there with a CD-36 had fuses installed? Had problems?
Matt
demers@sgi.com
-
matt cawthorne
Re: Battery Fuse size for Perkins 4.108
Larry,
Thanks for the feedback. What I meant by not requiring fuses between the engine and starter is that a boat meets ABYC standards if there is no fuse between the battery and starter. Also a boat meets ABYC standards if the positive feeder has a fuse within 72 inches of the battery. The 7 inch dimension is for wires leaving the selector switch. That wire can be 40 inches if it is everywhere inclosed, like behind an electrical distribution panel. That said, we had a small electrical fire on a Pearson that I once rented. As Wayne mentioned below, fire is a very scary thing on a boat. After having seen how much heat can come off of a small wire, I would hate to see what would happen to the battery cable shorted across the paralleled batteries.
Now, the battery cables that came on the boat were number 4's. They were rated at 160 amps, and lasted for 15 years with no overloads. The battery switch on the boat is only rated for 360 amps (intermittent). I have switched to number 2 battery cables, rated at 210 amps. I was thinking something like a 200 amp, Class T fuse might do the trick, but that type of fuse lasts 10 seconds at 600 amps before buring out. That could mean 1200 amps to the battery switch for 10 seconds in the event of a short. That seems like too much.
I had the idea after reading some other posts that perhaps a battery switch could be mounted to bypass the fuse for use in emergency conditions. Hmmmm......More thinking to do.
Matt
mcawthor@bellatlantic.net
Thanks for the feedback. What I meant by not requiring fuses between the engine and starter is that a boat meets ABYC standards if there is no fuse between the battery and starter. Also a boat meets ABYC standards if the positive feeder has a fuse within 72 inches of the battery. The 7 inch dimension is for wires leaving the selector switch. That wire can be 40 inches if it is everywhere inclosed, like behind an electrical distribution panel. That said, we had a small electrical fire on a Pearson that I once rented. As Wayne mentioned below, fire is a very scary thing on a boat. After having seen how much heat can come off of a small wire, I would hate to see what would happen to the battery cable shorted across the paralleled batteries.
Now, the battery cables that came on the boat were number 4's. They were rated at 160 amps, and lasted for 15 years with no overloads. The battery switch on the boat is only rated for 360 amps (intermittent). I have switched to number 2 battery cables, rated at 210 amps. I was thinking something like a 200 amp, Class T fuse might do the trick, but that type of fuse lasts 10 seconds at 600 amps before buring out. That could mean 1200 amps to the battery switch for 10 seconds in the event of a short. That seems like too much.
I had the idea after reading some other posts that perhaps a battery switch could be mounted to bypass the fuse for use in emergency conditions. Hmmmm......More thinking to do.
Matt
mcawthor@bellatlantic.net