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Old 14-01-2011, 09:55   #1
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Fuses vs Circuit Breakers

Building a battery switch panel that will incorporate circut protection for several items.

Main large draw items will be windlass (50A), 800W inverter (100A), stereo amps (TBD), house panel feed (?A) and a couple lower draw full time 12v accessories; bilge pump, mercathodes.

What is the deciding factor for what type of breaker is to be used?
I'd prefer to use the standard type of breaker: http://bluesea.com/category/3/10/pro...ne/overview/23
over these types: 185-Series Thermal Circuit Breaker Panel Mount - Blue Sea Systems

Cost is not a factor here. Both types are availabe in the amp ratings I need, which leads me to believe either are just as capable for the applications. Unless I'm overlooking something. Fuses are my least desireable choice.

Thanks
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Old 14-01-2011, 11:18   #2
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magnetic Hydraulic types are in general preferred over thermal breakers. Hence the first type is better. Note that these Bluesea ones are just rebadged Carling breakers, available from any electronics distribution at a lot less cost.

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Old 14-01-2011, 17:46   #3
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Thanks!

Yes, I noticed the Carling name on the breakers Certification sheet.... on the Blue Seas site itself.
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Old 14-01-2011, 18:18   #4
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Since price is not a concern then get breakers.
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Old 14-01-2011, 18:34   #5
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http://www.littelfuse.com/data/en/Te...Tech_Topic.pdf

A fuse is more reliable. lower cost, faster to operate (hence greater protection to the load device) By all means put a circuit breaker in when you will need a switch because it can provide that function, but for a windlass 20+ feet from the battery?
Fuse it also. Same for the inverter (unless it is already fused internally).

Not all change is progress, circuit breakers have some great convenience advantages but put fuses on those two items.
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Old 14-01-2011, 18:41   #6
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Crikey that was a fast response,

How is it faster? It takes less time to activate. Check a few numbers I*2t, when there is a fault and it needs to blow to protect the equipment the fuse blows faster.

Did you mean why is it faster?
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Old 14-01-2011, 19:45   #7
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Quote:
Originally Posted by David M View Post
Since price is not a concern then get breakers.

I didn't want the price to be a factor for this discussion. Although those breakers do add up fast. However, I'm only looking at 6-7 of them. I'm going to base my design off the Blue Seas battery switch panels, with a couple changes tailored to my needs. Been reading alot in the tech section of the BS site as far as ratings, ignition protection and what nots. Very informative, yet mind boggleing for the novice. It helps to get replies here that point me in the right direction for my researching.



I do have situation I'm not sure about:
I have the 50A thermo breaker that came with my Lewar windlass. I installed it at the helm for convienence so that it can be reset in an instant if need be. Approx 15' of wire from windlass to that breaker. (My boat is only 32' OAL) I need to install a breaker, or fuse, on the panel I'm making that will be located in the engine compartment to protect the wire between the battery and the helm breaker. This one will have a higher rating (wire dependent). To gain access this new panel in the bilge requires a little more effort, hence the use of 2 breakers. Am I on the right track in my thinking here, or should I remove the helm breaker altoghter?

cuthbert, thanks for the link. As stated, in the research stage right now. BlueSeas came out with a new 150 SafteyHub that would be perfect as far as fuse sizing and spaces capabilties.
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Old 14-01-2011, 20:39   #8
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Extra breaker is redundant and unneccessary, but something needs to fill that hole in the helm station, I'd leave it if it hasn't added greatly to the wire length, if it has leave the breaker as a hole filler and reroute the wire. Wire length is the biggest enemy of low voltage d/c. As for the speed of fuses vs breakers, it depends on choices there are fast blow, slow blow, time delay etc. apples and oranges. I have rewired 2 boats with blue sea panels, and am quite satisfied. Good luck
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Old 14-01-2011, 22:25   #9
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Extra breaker is redundant and unneccessary,
Not really correct. OP was correct in his assumption that he needs to protect the conductor from the battery to the Lewmar CB. The most strict requirement is that a conductor must be protected within 7" of its attachment to power. 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

Hope this helps.
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Old 15-01-2011, 15:39   #10
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Obviosly you misunderstood my English Charlie J, I said the one on the helm station would be redundant and unneccessary, not the one at the source. Sorry for your confusion. We here in the Western US quite often fail in communications with the rest of America, again, my appologies.
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Old 16-01-2011, 06:43   #11
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Originally Posted by capnorv
Obviosly you misunderstood my English Charlie J, I said the one on the helm station would be redundant and unneccessary, not the one at the source. Sorry for your confusion. We here in the Western US quite often fail in communications with the rest of America, again, my appologies.
Circuit breakers are a far better solution then fuses. Don't fuse things like windlasses use high power breakers. The last thing you be is to be scrabbling around for fuses when you may need the windlasses. Fuses are old hat.

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Old 16-01-2011, 07:20   #12
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capnorv-I lived on the Left Coast from sometime and understand the dialect pretty well. You did not answer the OP's question regarding the unprotected conductor from the engine room panel to the thermal breaker supplied by Lewmar. But you did say that
Quote:
Extra breaker is redundant and unneccessary
not clearly indicating which breaker you consider redundant.
goboatingnow-In general I agree that circuit breakers
Quote:
Circuit breakers are a far better solution then fuses.
However, in this particular case, I was trying to reinforce the OP's statement
Quote:
to protect the wire between the battery and the helm breaker. This one will have a higher rating (wire dependent). To gain access this new panel in the bilge requires a little more effort, hence the use of 2 breakers.
and provide him with an alternative, simple and cost effective solution to protecting the conductor that he asked about.

Hope that this clarifies Post #9.
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Old 16-01-2011, 08:01   #13
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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)

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Old 16-01-2011, 09:22   #14
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capnorv-I lived on the Left Coast from sometime and understand the dialect pretty well. You did not answer the OP's question regarding the unprotected conductor from the engine room panel to the thermal breaker supplied by Lewmar. But you did say that not clearly indicating which breaker you consider redundant.
goboatingnow-In general I agree that circuit breakers However, in this particular case, I was trying to reinforce the OP's statement and provide him with an alternative, simple and cost effective solution to protecting the conductor that he asked about.

Hope that this clarifies Post #9.
Charlie
Still having a problem following the conversation in it's entirity hey Charlie. Two breakers are not needed in series on one line, ihe one he is adding will protect entire circuit, hence one currently installed becomes redundant, and length of wire run is still the enemy of high amperage/low voltage wire runs, something I hope you can agree with, probably not.
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Old 16-01-2011, 09:57   #15
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Still having a problem following the conversation in it's entirity hey Charlie.
Not at all.

Quote:
...something I hope you can agree with, probably not.
I would suggest that you look at some of my other posts and contributions to CF before attempting to characterize my technical capabilities.

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