Fuses vs Circuit Breakers

[capnorv]

Your technical abilities are not what I question, only your hostility. I resign from this thread. Try to have a nice Sunday.

[US1Fountain]

Originally Posted by goboatingnow

My recommendation would be to use one main breaker near the source. But if you like the idea of the helm breaker then assuming the wire sizing is OK then use a higher rated breaker to protect the run to the helm however in an overload either one or both could randomly go. ( so the handiness of the helm one could be moot)

Dave

I'm not understanding what would create a 2 breaker trip situation.
If the windlass has a high draw (jammed or anchor hung up), I'm assuming it would trip the helm breaker, as it would be the lowest rating, leaving the higher rated engine compartment breaker intact for the wiring protection. Correct? Is there any harm in leaving the helm CB in? It's not but a 5 min procedure to remove it if recommended to go w/o.

Thanks for the responses all,
Jerry

[goboatingnow]

It depends usually the first breaker may not trip if it's rated high enough. But then you don't want it too high or in practice it's not protecting anything. Some of the windlass overload currents are very high and hence one or the other or both could trip. What you really want is a remote resettable breaker. Carling make them, a little on the pricy side !

Dave

[CharlieJ]

As I previously posted:

I have found that the simplest and most elegant way to meet this requirement is to install a Blue Sea Marine Rated Battery Fuse (MRBF) fuseholder and fuse on the B+ terminal of the battery or on the B+ bus bar. Here is the link for the fuses Terminal Fuses (MRBF - Marine Rated Battery Fuse) - Blue Sea Systems and for the fuseholders: Terminal Fuse Block, 1 Terminal Stud - PN 5191 - Blue Sea Systems

If you coordinate the protection between the MRBF and the Lewmar breaker, you will have a trouble free system.

Charlie

[US1Fountain]

A couple follow up questions pertaining to the battery to helm circut breaker wire protection.

I'm going to leave the 50A breaker at the helm for the windlass overload, quick reset abilty.
The size of the wire used is 4ga, to meet distance/load/voltage drop. (actually 6ga would have met the requirements at the end of the scale, so I went up to 4ga for even a less voltage drop) Blue Seas recommends a 100A fuse max. will protect that sized wire considering the number of conductors bundled and inside engine compartment specs, which is higher than the 50A CB.

question 1:
Will a 60-70A fuse at the battery have any effect (loss) of voltage/amp in the wire, vs. using a 100A, other than the obvious of a more protected wire? I'd prefer to use the lowest rated fuse as poosible, but not too low that it will blow before the CB will trip. The current draw of the windlass is spec'd at 35A.


question 2)

Would 4 or 6 power wires ran together, but openly (no wire loom usage, nor twisted) and supported by wire cushion clamps and wire ties constitute a bundled description? I'm not gathering a clear description of what is considered 'bundled'.

Thanks.
Jerry

[CharlieJ]

Q1:

Will a 60-70A fuse at the battery have any effect (loss) of voltage/amp in the wire, vs. using a 100A, other than the obvious of a more protected wire?

A1: No.

Q2:

Would 4 or 6 power wires ran together, but openly (no wire loom usage, nor twisted) and supported by wire cushion clamps and wire ties constitute a bundled description?

A2: Yes.

Now that you have the short answers, here is a bit of discussion.

Q1/A1 Elaboration: The ampacity for AWG 4 in machinery spaces in a bundle of up to three current carrying conductors is 95 amps. The National Electrical Code (NEC) is used for the basis of the ABYC Standards. Both of these were utilized by Blue Sea Systems in developing their fuse selector. We are permitted, for a variety of reasons, to use a larger over current protection device (OCPD; fuse or circuit breaker) if the ampacity of the conductor is less than a commonly available OCPD. That said, I would install either:
> an MRBF (75A p/n 5180)
> an ANL fuse (80A p/n5124)
> or a MIDI fuse (70A p/n 5254)
with their associated fuse holder as the first OCPD off the battery or bus bar. All of these have an AIC >/= 5000A and are appropriate for this service.

Q2/A2 Elaboration: The NEC and the ABYC provide tables for derating conductor ampacity based on the temperature of the environment and bundling. The ampacity rating of the cable is limited by the capability of the insulation to remain solid and insulate the conductor. Conductors marked as "Boat Cable-BC5W2-UL 1426" have a temperature rating for a single conductor in free space of 105C. Bundling of conductors inhibits the ability of the conductors to release the heat naturally generated when a current is passing through them. The NEC utilizes derating factors based on environmental temperature and how many current carrying conductors are bundled. For DC circuits, the ABYC has only two tables for derating based on temperature and number of conductors bundled while the NEC's derating factors have a much finer granularity. The ABYC is currently (no pun intended) working on improving on the derating factors published in the E-11 Standard.

Hope this long winded explanation helps.

Charlie

[goboatingnow]

I would countenance against having a fuse of anytype on a windless. Better simply not utilise the helm one and put in a proper sized CB near the power feed takeoff point , Scrabbling around looking for a fuse when the windlass is stalled out ( usually in conditions that need it to work) is not something to be countenanced.

Dave