Circuit Breakers

[pfuller Lurker Find all posts View Profile Close pfuller]

I plan on putting a 50Amp circuit breaker(manual reset) near the crank battery before the run of 6 B&S to the rear to an andersen plug (which will be used to charge a van battery).

Will the smaller plastic circuit breakers do the job? e.g. handle the current and not result in voltage loss.

http://www.ebay.com.au/itm/NARVA-50-...QAAOSwLVZVrGI0

Or should i get the heavy duty ones, like this:

http://www.ebay.com.au/itm/NARVA-HIG...cAAOSwPcJVSA4z

[Guest Close Guest]

I use the first one with no issue

[Brodad Junior Member Find all posts View Profile Close Brodad]

The lowest available second type ones are 60 amp, and both are auto reset

[seenthelight Junior Member Find all posts View Profile Close seenthelight]

I run 2 of the http://www.ebay.com.au/itm/NARVA-50-...QAAOSwLVZVrGI0 ..
One close the the battery in the car and one close the battery in the camper.

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

Both will work - however be aware the auto reset type will do exactly that. Even if the short remains it will reset and send power to the short, heat up the bi metal strip (takes about 1/2 second). Keep doing this and you could have a fire and a flat battery.

My electrical engineer (son) tells me always use a reset able circuit breaker or fuse.

When i had our trusty 80 series i had a reset able breaker on the power lead to rear and one one the battery on the trailer. The cable shorted to chassis on a sharp edge that i didn't see and resulted in the breakers both clicking away for several hours = result of melted plug between car and trailer and flat battery on trailer. The lead was so hot i burnt my fingers. That was the last time i used auto reset breaker. Must have been that close to catching on fire it wasn't funny.

Rusty.

[Brodad Junior Member Find all posts View Profile Close Brodad]

Whats wrong with using fuses?

[craigm Addicted PP Member Find all posts View Profile Close craigm]

I run the reset-able circuit breakers to the 2 feeds i have running down the back to my power box in the rear and Aux power (Solar panel input or inverter out as req'd) I also use them at the batteries between my dual battery system. Why I prefer reset-able? So I can isolate power quickly and easily. I only have the power energised to the rear when I have gear in the back so reset-able breakers are have the go for me...

Under the Bonnet

[pfuller Lurker Find all posts View Profile Close pfuller]

Thanks for the replies.

Using the bigger manual reset circuit breakers as an isolator switch is a good benefit of that type.

By the looks, the smaller plastic ones only have a small inset button to reset them after they have tripped.

Either way, my main concern is voltage drop through them. Has anyone tested voltage drop through the smaller one?

[Mr ok Lurker Find all posts View Profile Close Mr ok]

I midi fuse may be a simple option. I believe fuses trip faster than circuit breakers, which i prefer given the potential high fault current. A blown fuse or circuit breaker trip signifies a problem and it shouldn't blow if the circuit is in good condition. As suggested by Rusty, auto resetting circuit breakers can keep tripping and resetting and you may not even notice a problem until it is too late. Best to use a trip device that needs attending to with the amount of current the cables can carry.

Your concern with volt drop is going to me more of a problem from using 6 B&S to try to charge a battery in a towed trailer. The length of the circuit is going to be 15 to 20 meters. At 30A of current you will see 0.6v to 0.8v drop depending on length. The voltage may not be good enough if you are alternator charging the battery in the van.

With my setup, I was able to get 3B&S (25mm2) into the 50A plug terminals so i ran one cable in conduit from the positive terminal of the battery to the plug. I also drilled and tapped the chassis at the rear to keep the (-) cable run short and use the chassis common ground. Just like Craig, i don't like having the large cable energised at all times at the rear of the car (next to the fuel tank) so i installed a cheap 200a relay and control it with an OEM looking "Camper Power" switch in the dash. The plug at the rear also has a weather proof cover with an LED indicator so i can see if the plug is energised.

[pfuller Lurker Find all posts View Profile Close pfuller]

Thanks for the Reply Mr OK.

I 'm just trying to think, what are the benefits of having a switch in the cabin to kill power to the cable run?

If the wires short, the circuit breaker/fuse would kick in. In fact, am i right in saying that unless there was a short, that no circuit would be created anyway??? (If nothing was plugged into the andersen plug?)

[Mr ok Lurker Find all posts View Profile Close Mr ok]

I just think it is better to turn off a 50A circuit when not needed. I used an OEM looking camper switch in the cab mostly because the switch looks cool and i have an empty spot in the dash. I could have mounted a switch to control the relay in the engine bay or use a manual breaker. It would do the same job and would have been easier to install.

Yes, a circuit will not be created until either something is plugged in, or the red wire rubs up against a metal part of the car. Unless the circuit can be switched off, potential difference (voltage) will always be present in the cable so the short circuit hazard will also be present. The main reasons why i didn't want the cable to not be live at all times is because it's a long, high current circuit running under the car that terminates at the rear next to the sub tank, and i drive a petrol! A good hit in the rear end that damages the fuel tank and cable at the same time may result in a fireball.

A short circuit at 50A will be energetic. There will be sparks/burning/melting before the fuse or breaker kicks in. I can't assume a safety device as big as 50A will trip immediately. If the short is (say a cable rubbing on the chassis) not making a good clean connection, less than 50A of current may flow intermittently and not trip the safety device immediately. This situation can continue to generate heat and cause more damage until more than 50A flows long enough to trip the safety device.

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

Front has circuit breakers - Rear fuse box has fuses.

The larger cable is 2AG to the rear fuse box, 16mm from rear fuse box to anderson and 6mm to the remaining appliances.

With this we get no noticable volt drop under full load.

In summery the circuit breakers are there to save the main cable, and the car from burning. The fuses are to save the equipment.
Its a bit like ' my injectors have never caused me problems' . One day they might, and it will cost you.