Electrical schematic

[BODs SR2]

Need an electrical schematic diagram for my boat. Very basic. Does anyone have an opinion on using separate battery isolators or a 1 2 both switch. Also does the starter motor solenoid circuit need fusing. Thanks. 

[nicknorman]

You need a 1 2 both switch only if that is the means of splitting the charging of one alternator to engine and domestic batteries. Otherwise I’d go for separate isolators as it removes the possibility of human error.

Better to have a split charge relay or VSR or two alternators and 2 isolators.

No, starter motor solenoid circuits are not fused, they just have to go through an isolator.

Edited January 5, 2018 by nicknorman

[BODs SR2]

Great, thanks. 

[reg]

If I can piggy back on this thread. I have twin alternators Is it a good idea to mega fuse these? At the moment I have isolator switches between alternator and batteries but can't for the life of me think why they are needed? 

I'm thinking of switching out the isolater switches for mega fuses, does this make sense? 

[Jen-in-Wellies]

10 minutes ago, reg said:

If I can piggy back on this thread. I have twin alternators Is it a good idea to mega fuse these? At the moment I have isolator switches between alternator and batteries but can't for the life of me think why they are needed? 

I'm thinking of switching out the isolater switches for mega fuses, does this make sense? 

Battery isolators are a boat safety scheme requirement, as is appropriate fusing. Take a look at the requirements before changing this.

Jen

[nicknorman]

27 minutes ago, reg said:

If I can piggy back on this thread. I have twin alternators Is it a good idea to mega fuse these? At the moment I have isolator switches between alternator and batteries but can't for the life of me think why they are needed? 

I'm thinking of switching out the isolater switches for mega fuses, does this make sense? 

No best to leave them as is. The isolators are a BSS requirement and useful to isolate all the wiring when work is done in the vicinity. Fuses are a bad idea because they can blow due to old age, and if a fuse blows when the alternator is working hard it’s likely to take out the alternator.

[reg]

Thanks 

Would of been a Double greenie if I could. 

Edited April 23, 2018 by reg

[cuthound]

I wouldn't fuse the alternator for the reasons Nick says, and you would still need the isolators to meet the BSS requirements as Jen pointed out.

When I worked in the critical power industry, fuses were preferred to circuit breakers, because of the closer protection they provide (they blow instantaneously at about twice rated current whereas circuit breakers trip at three to five times rated current). They were however changed routinely every five years to eliminate age related failures.