Calling all 12v Gurus

Thanks so much would use auto reset circuit breaker or Fuse

I would personally use a fuse in any such situation. Auto-resets can/will reclose on a fault (they don't know the fault is still there until they reclose ...).

In my case - a (20A) Redarc BCDC1220 - I have 40A fuses at the cranking battery takeoff and in the tails coming off the aux to the adjacent Anderson connector. My fridge line has a 30A fuse, but it also protects a ciggie-lighter outlet adjacent.

Apart from the type of application Allan mentioned, self-resetting breakers ("reclosers") are used in high voltage transmission lines as protection against transient faults such as lightning strikes. But the key word there is TRANSIENT.

I was once involved in a power line that was about 5km long, and in serious termite country so the poles and cross-arms were steel. At one change of direction, Corellas seemed overly inclined to stand on the cross-arms and scratch their beaks on the nearby conductors. After the bang, as they fell to the ground in a charred state the line protection would kick in. We used "three-shot reclosers" (technically 3-shot interrupters) which would open, then reclose. If the fault was still present, open and reclose again. A third opening would result in staying open, as it indicated an ongoing (non-transient) fault. In the first year of operation, over 300 "hits" were recorded but the line was never left open.

Self-resetting always incorporates a risk element, which can be serious if left unattended to just cycle. Although they were used in motor-vehicles 50-60 years ago (think Holden, headlight pull-switch assembly) I would personally never use one in my vehicles. Others may think differently of course.

They are recommended to be used in electric brake controller circuits.

If you use a fuse and it blows the trailer will have no brakes and you wouldnt know,

Redarc recommend one be in the power circuit from the battery.

.
The question that needs to be asked Tom, is "Why would the fuse blow"? Provided that it has been correctly sized then the reason must be a short-circuit. In which case re-applying the supply would achieve nothing other than the re-closing circuit breaker opening yet again and repeatedly. The brakes still would not be working.

Actually Tom, Redarc instructions simply state "Fuses or Circuit breakers of appropriate rating must be installed to protect the vehicle system."
They do however offer a self-resetting circuit breaker (CBK30-EB) in an accessory kit.

I have emailed Redarc to ask their reason for a self-resetting CB.

Dont know where you saw that as here are the instructions for Redarc brake controllers both the old type and the new Towpro

https://www.redarc.com.au/wiring-diagrams/wire-up-your-tow-pro

Neither mention fuses. The only one that does is the 24/12 volt model

Neither do Tekonsha as per these diagrams

I was specifically told never to put a fuse in a brake circuit so I didnt.

I presumed that it was that even if you had a fault a breaker may allow some braking whereas a fuse wouldnt

.
I guess it's where you look Tom.
The following is copies\d from Redarc's EBRHV2 Manual online............

"3. Fuses or Circuit breakers of appropriate rating must be installed to protect the vehicle system. Please refer to the installation instructions on page 6 for specific instructions on where to install Fuses or Circuit Breakers and for appropriate Fuse or Circuit Breaker ratings. Fuses must be installed as close as possible to the battery."

If you do have a short circuit in the supply line then even a circuit breaker will not "allow some braking".

I have yet to receive a response from Redarc on this.

Wonder why they write that and in all the wiring diagrams show ONLY circuit breakers. Maybe the office girl wrote that one.

From the "Etrailer " Site

For brake controllers we do not recommend that fuses be installed in place of circuit breakers. One reason for this is that an auto reset circuit breaker will reset if there is an intermittent short, once the short is no longer present on the circuit, and braking performance would be restored. With a fuse, once blown, braking performance is terminated until the fuse is physically replaced.