Blue Sea circuit breaker vs Mega fuse, etc.

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syvictoria

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Hi. Aside from the difference in cost, would a good quality circuit breaker such as the Blue Sea 285 series one:

https://www.bluesea.com/products/7087/285-Series_Circuit_Breaker_-_Panel_Mount_100A

be suitable for use as over-current protection at a 12V domestic battery bank? The cabling is 35mm2/2 AWG. There are LOTS of threads on here about main fuses, but less so about main CBs.

I understand that there is a risk of CB contacts welding themselves together at very high currents, but this Blue Sea CB has an interrupt capacity of 3000A @ 48V.

Thanks!
 
I use circuit breakers on all commercial work as fuses are generally "not allowed" because people do all kinds of silly things if they blow :rolleyes:

Ref pleasure boats, a lot of our more prestigious work, I will also specify with breakers as cost allows due to the fact of them being more useable and "professional". Nothing wrong with MEGA fuses instead but more work should a fault or over-current incident appear. Good to keep spares onboard or better still, cable tie a spare near each fuse holder securely.
 
syvictoria said:
Hi. Aside from the difference in cost, would a good quality circuit breaker such as the Blue Sea 285 series one:

https://www.bluesea.com/products/7087/285-Series_Circuit_Breaker_-_Panel_Mount_100A

be suitable for use as over-current protection at a 12V domestic battery bank? The cabling is 35mm2/2 AWG. There are LOTS of threads on here about main fuses, but less so about main CBs.

I understand that there is a risk of CB contacts welding themselves together at very high currents, but this Blue Sea CB has an interrupt capacity of 3000A @ 48V.

Thanks!
Click to expand...

In passing on Ebay, only different mounting, https://www.ebay.co.uk/itm/30-150A-AMP-Circuit-Breaker-Car-Marine-Stereo-Audio-Inline-Replace-Fuse-12V-42V/392201885011?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D58656%26meid%3D0043655b14a64076a30d0a7ea30c10bb%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D401771811869%26itm%3D392201885011&_trksid=p2047675.c100005.m1851

I wonder sometimes were the difference lies.

Brian
 
The relatively low interrupt capacity of 3000A is the issue. Main battery fuses are usually double (or more) this number.

It is important because in the event of a short circuit (which the issue you are trying to interrupt with the main fuse or circuit breaker) if the batteries and wiring are capable of delivering more than 3000A, even for a fraction of a second the circuit breaker can be welded closed and will not interrupt the short circuit even if the current subsequently drops well below this number.

There are formula that indicate if an interrupt capacity of 3000A is sufficient. This depends mainly on the battery bank size and composition (A larger battery bank can deliver a larger current. ) together with main battery cable size. You don’t indicate your battery bank size and I would need to look up the relevant tables, which unfortunately given my poor internet connection is difficult. However, while 3000A sounds very high it is the low for anything but a very small marine battery bank. Even a single battery can very briefly deliver 1000A-2000A in the wrong circumstances with a dead short.

Most marine battery banks require main fuse protection with an IC of around 6000-10000A. An IC of 3000A may be just OK for a small battery bank but the more common ANL or even better a class T fuse with its higher IC is generally needed for most marine installations.

Fuses or circuit breakers with a lower IC rating are fine on a secondary circuit providing the main battery feed has circuit protection with an adequate IC rating.

The circuit breaker you have indicated is mainly used for secondary circuits in marine installations. A primary fuse would normally be fitted providing the required IC capacity. With a small battery bank the indicated circuit breaker may be just acceptable as primary device but it will be marginal at best.
 
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those breakers are rebranded. available much cheaper on ebay/amazon at about £10 (no difference). i used those on my boats wiring system and they are excellent
 
UK-WOOZY said:
those breakers are rebranded. available much cheaper on ebay/amazon at about £10 (no difference). i used those on my boats wiring system and they are excellent
Click to expand...

They are indeed rebranded, they are made by Cooper Bussman. Can you post a link of the Cooper Bussman ones for £10 please ?
 
noelex said:
The relatively low interrupt capacity of 3000A is the issue. Main battery fuses are usually double (or more) this number.
Click to expand...

Thank you for this thoughtful reply. I for one certainly didn't appreciate the extremely high if momentary current my batteries could deliver. I shall now go and check that there is a primary fuse
 
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