circuit breaker position

[dnej]

I would like to add a circuit breaker to my electrics.
I have two batteries, mounted at the stern,going through a 4 position isolation switch, also stern mounted.

The common outlet of the switch,goes to a buss bar, and then distributes to the starter motor.
A line also runs to another buss bar,at the back of the helm firewall, of the cuddy cab.
From that bar,there are leads that go off to two X 4 gang switches,with fuses,and also a addition fuse box,for items not on switches,such as DC outlets,two way radio,AM FM etc.

Where is the best place to add a high current circuit breaker, or is my thinking not necessary, in my situation.
David

[finga]

The best place to put a circuit breaker and any current interruption device is as near as possible to source of the supply.
So if you want to protect the supply cable going to behind the helm the best place is as close as possible to the rear distribution busbar or battery switch.
Personally I'd be getting rid of the rear busbar and put both cables on the common of the battery switch. Less joins or connections as possible is the go with boats. Less hassles later that way.
When you say high current...what value are we talking about Dave??
If you want I could wander on down and have a sticky-beak.
Just give a cooee if you want that
Cheers then
Scott

[dnej]

Finga,
I was thinking of a 70 amp ,tripping within 1 minute, at 90 amps.
The main reason for the buss bar, was to connect the pos from the motor ,to the pos from the isolation switch, as the motor cable was short 30 cm,or so.

A battery type cable ,runs from the switch common,to the bar,and the motor pos,is connected to the same post,on the bar.( Acts like a stud) This bar is in a box,with lid,under cover,and connections are coated with lanolin grease.

So the bar will stay,but I could connect the secondary supply to the switch,if there is room,as they dont give you much thread.
Thanks for the positioning comment.
I suppose the main issue is,if the breaker throws,on a supply line,which item is causing the problem.

I am fine for the moment.Thanks for the offer.I will let you know about the switches,as I am only in the planning stage as yet.
Did you see my entry re looking after that boat?
David

[finga]

Mate, if the busbar is in a sealed box with lanolin smothered then no problems.
The breaker will OK in there as well.
The 70A is probably a bit over board though for auxiliaries. An average house runs off a quick blow 60oddA fuse.
Bung the auxiliary feed cable onto the busbar seeing it's a goodun'. Might as well bung the breaker in there as well if it's big enough. Lanolin spray would be good to drown the breaker with.

If the breaker throws and none of the auxiliary breakers/fuses are gone then the problem would be from the circuit breaker to the distribution point behind the helm.

A lot of problems are created by not having the feed from the battery/s to the auxiliaries fuse panel/s not protected. If there is a fault a fire can occur or short circuit current conditions could blow a battery or two.

I did see the "looking after that boat". Might be a good business for somebody to set up.
Of all the boats in marina section of Raby Bay my brother has seen only about 1/2 moved since he moved there last November.
Good luck with the wiring

[dnej]

Finga, so what about say a 30 amp unit,auto reset type? Does it matter, if I go to the 70 amp,even if not warranted in real terms. After all,it is only a short circuit protection.
In regards to Anderson plugs, installed on M.V tow bar,for use with loading winch,is 50 amp sufficient.I cant get any power drawer details off the winch, and I have rung around to no avail.
David

[finga]

30A auto reset when be pretty good in that box down the back I'd say.
I have some 40's in the auto reset here as well if you want bigger.

Call in and grab my DC ammeter and you can load the winch up and check the current drain and also assess what current drain you have when all the aux. are on in the boat.

Easy to gauge what you need wire size and CB size wise then.