Overcurrent protection

[Panhandler]

All,

I would like to install overcurrent protection for the two house banks. 4awg wire was used with a temperature rating of 105c, but the wiring for the banks is bundled. It is my understanding from reading Nigel Calder that an 80amp breaker of fuse would be appropriate on each circuit as they run in the engine space, but then multiply by .7 because they are bundled so ~56 or rounded up to 60a. Calder states that the fuse or breaker should not be right with the batteries due to fumes and corrosion. However, it seems to me that the easiest way would be to put a fuse right on the battery terminal and then run the cable from it. What is the correct way to handle this?

Thanks for the help! This forum has already been an incredible wealth of information!

What about these MRBF Terminal Fuse Blocks combined with 60a fuses? http://www.defender.com/product3.jsp?path=-1|328|2290021|2290030&id=983740

 

[Bacchus]

All,

What about these MRBF Terminal Fuse Blocks combined with 60a fuses? Blue Sea Systems Single MRBF Terminal Fuse Block

I think they are the way to go... I believe ABYC states overcurrent protection should be w/in 7 inches from batt'y and for large cables i think they are easier than inline (no addn'l crimps req'd)

HopCar here on TF should be able to supply them if interested.

 

[kchace]

All,

I would like to install overcurrent protection for the two house banks. 4awg wire was used with a temperature rating of 105c, but the wiring for the banks is bundled. It is my understanding from reading Nigel Calder that an 80amp breaker of fuse would be appropriate on each circuit as they run in the engine space, but then multiply by .7 because they are bundled so ~56 or rounded up to 60a. Calder states that the fuse or breaker should not be right with the batteries due to fumes and corrosion. However, it seems to me that the easiest way would be to put a fuse right on the battery terminal and then run the cable from it. What is the correct way to handle this?

Thanks for the help! This forum has already been an incredible wealth of information!

What about these MRBF Terminal Fuse Blocks combined with 60a fuses? Blue Sea Systems Single MRBF Terminal Fuse Block

The *conductors* running through engine spaces should be derated, and derated further if they are bundled, but regardless of what the wires can "carry" it is prudent to limit the fuses to the max expected circuit current. If after doing the "derating" math the max conductor current is not sufficient, then you will need to upsize the conductors or not bundle them or don't run them through engine spaces.

I have swapped all my battery fusing over to those "Terminal fuses" They are ignition protected, don't require extra wiring, available in 30-300A sizes and take up the least amount of space. BTW - they are made by Buss and available at Delcity for a fraction of the cost from Blue Sea Systems.

Marine Rated Battery Fuse Block

Ken

 

[Panhandler]

Thank you both. Looks like the way to go.

 

[Phil Fill]

Your boat might already have them as they been recommended back in the 1970. The eagle is 1978 and has them. 600 amp for the start and 60 for the house and 30 for the inverter about a foot from the battery. Had an insurance audit and the first thing check where the battery fuses. We did not have one on the inverter. Another was AC breaker between the shore power boat plug and the main planel selector switch which the Eagle did not have, and most older boats do not. Not having is the cause of many boat fires. He found 19 problem items which we had 60 days to correct bring up to code.

 

[Panhandler]

Your boat might already have them as they been recommended back in the 1970. The eagle is 1978 and has them. 600 amp for the start and 60 for the house and 30 for the inverter about a foot from the battery. Had an insurance audit and the first thing check where the battery fuses. We did not have one on the inverter. Another was AC breaker between the shore power boat plug and the main planel selector switch which the Eagle did not have, and most older boats do not. Not having is the cause of many boat fires. He found 19 problem items which we had 60 days to correct bring up to code.

Thanks, Phil. Purchase survey indicated no overcurrent protection but she does have an AC breaker between shore power and the main panel. It's an odd combination of recent upgrades and old holdovers! I'll take a more serious look at the wiring when we get her back to our dock in Pensacola from Melbourne. It seems as if some simplification may be in order, particularly in terms of isolating batter banks. The big Cat has two 8D starting batteries, the gen has two big starting batteries, and then there are two house banks...all charged by one charger.... Love your boat, btw!

 

[Phil Fill]

Thanks, Phil. Purchase survey indicated no overcurrent protection but she does have an AC breaker between shore power and the main panel. It's an odd combination of recent upgrades and old holdovers! I'll take a more serious look at the wiring when we get her back to our dock in Pensacola from Melbourne. It seems as if some simplification may be in order, particularly in terms of isolating batter banks. The big Cat has two 8D starting batteries, the gen has two big starting batteries, and then there are two house banks...all charged by one charger.... Love your boat, btw!

We stayed at Orange beach two weeks ago. We are looking at different areas for the winter. Puget sound on the boat in the summer and winter south. Make sure you added the AC breaker, shore and gen set. Make sure they are double throw.

 

[Panhandler]

We stayed at Orange beach two weeks ago. We are looking at different areas for the winter. Puget sound on the boat in the summer and winter south. Make sure you added the AC breaker, shore and gen set. Make sure they are double throw.

Thanks, I'll double check. We'll rent you some cheap dock space in Pensacola!