Circuit breaker size

[Mile2885]

I tried the search and didn't find my answer so I'm turning to the pros.  I'm in the process of adding the Blueseas add a battery kit with ACR.  I'd like to add the circuit breakers instead of fuses and am wondering if I'd be better off going with the Blueseas 120A Series 285 breakers or the 100A breakers.  I'm using size 4AWG from Greg's for  the battery cables.  Bluesea's directions say for the ACR  and 4 AWG to go with a 110A fuses.  Charging system is off of the Honda BF135 and the 9.9 kicker also  has a charging plug.  Thanks in advance. 

[DevMah]

I believe you alt output is 40A correct me if I am wrong.

Depends on the ACR.... and Output of the Alternator.

Mini ACR 7601 min wire size AWG 8 charging up to 50 A is a 60-65A fuse.
resource http://assets.bluesea.com/files/resources/instructions/980014350.pdf

The 7610 larger SI ACR min wire size AWG 6 charging up to 60 A is a 75-90A fuse
resource http://assets.bluesea.com/files/resources/instructions/990170140.pdf

Depends on current (A) and length of wire to determine the conductor size.

So with the mini 60-65 Amp breaker and with the larger Si ACR 75-90A breaker. (using the above wire sizes)

I realize you confusion reading this resource http://assets.bluesea.com/files/resources/application_briefs/app_brief_selecting_fuse.pdf
But if you read carefully is dose ask charging amps then states a min wire size.

Dev

[Mile2885]

Thanks for the info.  I'm running the standard size, not mini should mentioned that earlier. 

[TJ Arima]

Going thru the same thing as you. Going 4AWG from my battery to ACR. Manual says minimum is 6awg. I have 40a alternator output from my 140 Suzi.

[Mile2885]

Ya,  I spoke with Greg (at least I think it was Greg) at Greg's wire.  He said anything over that will be way overkill. I took his word for it.  Now I'm trying to cleanly cram everything in place.

[Mile2885]

So to be clear before I order, I should  be between 75-90A?  I think you're correct on the charging output.

[T-Rex]

Size your fuse to protect the wire !!
Its that simple.

[DevMah]

As I don't know the wire size you decided to use... did you use the min or go thicker?
If you know your condutor size just go to the link.

Pick the correct wire size using the Max Amps defined from Blue seas  then the total length of conductor run (see link below)

Example:90A draw, up to 6' at a 3% voltage drop and draw  will require a AWG 4  marine grade conductor.

Now with the Awg 4 you will be able to determine the fusing. (for the above example outside engine room 150A ,125A for inside engine room)

Please follow this link:
http://assets.bluesea.com/files/resources/reference/20010.pdf

FYI
Usually branch circuits are designed  using max operation Amps and length of conductor (taking into consideration voltage drop). Once the conductor is sized the appropriate fusing can be chosen. In some cases the branch circuit fuse can be way below specified . For example your bilge pump may have a 5A fuse protecting the device off the branch as there is no secondary fuse at the component itself but has a wiring circuit capable of 10A. This is common practice for manufactures as they minimize the wire sizes to save cost on wiring and inventory.

The general term "Size your fuse to protect the wire" dose not always hold true. I would rather say "Size the fuse to protect the circiut".

In TJ"s case many of his circuits going from the Helm fuse panel may have devices that do not have secondary fusing at the end device. As he is going with a larger conductor that can  handle more current than the device itself, his fusing will have to be set as per the device manufactures recommendation.(possibly lower than the wire capacity)

Dev

[T-Rex]

I have no idea why Branch circuits were brought up (and i don't think we need a confusing explanation as to why)

As i said... Size the fuse or circuit breaker to protect the wire...

Honda BF135  -   (40 A charging circuit)


Blue Seas ACR model 7601 (up to 65 A) (perfect for this job)


8 or 6 awg wire is plenty for this particular install.



50-60 A fuse or breaker is perfect, above alternator max current and well below max wire rating.  :biggrin:

One more thing to consider...
The ACR has internal protection but i would fuse it to meet the ABYC Ampere Interupt Rating according to the CCA of your particular battery.

"The interrupt rating of a fuse or circuit breaker is the maximum short circuit current that an overcurrent protection device can safely interrupt under test conditions. The interrupt capacity is the highest current the device can safely interrupt at the rated voltage.

In extreme cases a fuse carrying an excessively high current can vaporize and the metal can be deposited on the base of the fuse block in a way that permits it to continue to carry current. Similarly with circuit breakers, if the level of fault current goes above a certain level the circuit breaker can become inoperable while still conducting current. Fuses and circuit breakers all have an interrupt rating as a measure of their ability to cope with these circumstances. For any given device the interrupt capacity may be different for AC and DC current and for different voltages.

For boats, the ABYC standards specify the interrupt capacity requirements.

For DC Systems of 12 or 24 volts the primary circuit protection (Main fuse or breaker next to the battery) is required to have an Interrupt capacity of 3000 Amps for battery banks from 650 CCA (cold cranking amps) up to 1100 CCA capacity and 5000 Amps interrupt capacity for larger battery banks."





Quote from another site:

"I called Blue Sea tech service yesterday to ask about my above question. The nice fellow I talked to said he needed to talk to one of their EE. He called me back and informed me that the fuses are there only to protect the 2 wires going from the ACR to the 2 batteries. In that I have a 60 Amp alternator on the Honda 225 he suggested to use a fuse (or circuit breaker) around 70 Amps."

[TJ Arima]

Good info TRex. Thank you

[DevMah]

T-Rex

My appoligies if i mis-understood your comment... but you had no mention of the device itself.

Size your fuse to protect the wire !!
Its that simple.

You had written the above not wire... (... signify s etc)

This was brought up in my first post with the recommended wire sizes and fusing, however we have two different installations. (TJ and Mile) TJ mentioned above that he was going to AWG 4 and Mile Awg 6 (correct me if I'm wrong). I wanted to clarify this to them using a branch circuit example as I don't know the confirmed length or AWG they chose. I don't like to assume things like run length and size.

Thanks for repeating the sizing in my first post with the min wire (I believe they are both using the larger ACR 7610 not the smaller one you posted 7601 the fusing will be larger as you have referenced  the incorrect model). Sometimes going to a thicker wire has more issues.

I sometime go into detail for  others reading this post so they can grasp what im saying. Not everyone catches on quickly..

Just like you It is difficult for me to sometime bring the technical grammar down to laymen's terms... Not every one can understand what we are saying unfortunately its up to the ones ability to interpret. As I mis-interpreted your comment due to grammar error.
Many times I explain things too technical and would seem to contradict. I have to learn not to be so long winded.
My apologies and anyone has questions PM me and I can call you and explain things over the phone.


Dev.

[DevMah]

My Apologies again to answer both installations

Mile I believe this  below holds true for you as long as your wire lengths are in accordance.

The 7610 larger SI ACR min wire size AWG 6 charging up to 60 A is a 75-90A fuse
resource http://assets.bluesea.com/files/resources/instructions/990170140.pdf

TJ I believe this holds true for you also but please confirm this with the manufactures rep.

I assume you both have less than 60A charging and less than 6' total wire length. (battery to battery)

Dev

[Mile2885]

Thanks all! This is very helpful!

[Markshoreline]

Dev I appreciate your layman oriented, dumbed down explanations because they make me think I can understand the electrical world a bit! Thank you.

[TJ Arima]

Dev, I too appreciate your help and expertise. Let me clarify my intentions. I made necessary changes to mine too maybe Mile can relate.

Both batteries to ACR- 1 foot, 2 AWG.
Start battery to batt switch -1.5 feet 2 AWG
House battery to batt switch- 1.5 feet 2 AWG
Battery switch (start battery side) to motor- factory Suzi Cable
Battery switch (house battery side) to Safety Hub 150- 1 foot 6 AWG
Safety Hub 150 to 12 slot fuse panel behind Helm- 16 feet 6 AWG 50a MiDI from one of Hub 150 slots
12 slot fuse panel behind Helm to Switched fuse panel on the Helm- 1.5 feet 6 AWG

This is POS side. Neg side will mirror these lengths. Between ACR and both Batts- 75a MBRF Fuse. No fuse between ACR and Hub 150 due to short length of cable.



Thank you

[DevMah]

TJ

Sounds awesome you are well on your way


Just wanted to awnser  Miles question on the circuit breaker. I personally  perfer the MBRF fuse for the ACR
As a fuse gives you a thermal break in the circuit. Dont get me wrong you can use a breaker but just know they could respond silghty slower.

As mentioned above that fuses and breakers sometimes melt and make contact. I have only personally seen this with cheap knock off  fuses and breakers. You pay for what you get, there is a reason why Buss, Blue Seas charge a premium, its beacause of high quality control and rigorous testing.

That being said my own Arima has the MBRF fuses and im sure im in the same boat as other users.

Please post some pictures as you go... many time a picture is worth a thousand words.

Best wishes

Dev

[T-Rex]

No fuse between ACR and Hub 150 due to short length of cable.

There shouldn't be a direct connection between the ACR & Hub 150

[T-Rex]

Unless your talking the ground ?
If that's the case throw an inline fuse in, its only a small wire so a fuse wont cost you much.

[DevMah]

I think he meant battery B+ and the hub.

[DevMah]

TJ

Please clarify this.

The ACR only has 3 connections
One at each battery B+ (2 connections fused )
And a fused connection form the ACR B-  connector to your Battery  (B-) bus bar. This size is specified by Blue Seas. This fused B- connection is the protection for the ACR itself.

Dev

[TJ Arima]

Yup my bad. No direct connection between ACR and Hub. I meant battery switch and Hub. I stand corrected. Thank for catching that TRex. Don't want to give out wrong info as I'm still learning

[Mile2885]

Done, had some extra starboard and apparently too much time on my hands.  Went with the MBRF on the battery instead of breaker.  Also changed location of switch.  Much easier to reach and see now. I like being able to reach over the side and turn battery on or off when on the trailer.    I have enough room on starboard to add my extra switch to isolate(turn off the ACR) if needed.  On the flip side,  it's like stuffing 10lbs of S$%! in a 5 LB sack with those batteries.  I'll be posting the old switch (new- used once- 9001e) and hole saw that's been used once on the classifieds. 

[TJ Arima]

Very nice, I like how you set that up. Great job!

[Mile2885]

Thanks.  Feels good to get it done finally. Tried to take advantage of some of the unused space. I also added a buss for the negative end off the system. It's nice not having all kinds of random things connected to the battery. I'll probably add a safety hub at some point  but I'll probably wait until the checking account stops smoking.