Unfused 16g disconnect wire

[AlexPeterson]

I see that our trailer has an unfused 16g wire going from the battery terminal on the frame to the trailer disconnect (brake) switch, and then back into the brake wire of the 7 pin. There is no fuse in this line. As I understand it, the 4 brakes at full voltage might draw around 14-16 amps. The 16g wire would indeed get a bit warm, but, if the trailer is disconnected that would be a minor concern. A more realistic concern is if the disconnect gets accidentally tripped. I plan to put a 20a fuse on this hopefully never used line.

Thoughts?

[howson]

AlexPeterson

Neither the Tekonsha nor the Fastway instructions (two models of breakaway switches) mention or show a fuse in the circuit. The Tekonsha specifically states to "wire per schematic"--which does not show any protective device (snip from manual below).

I, too, sometimes worry about a prangster pulling the emergency breakaway pin when I'm not at the camper. (It would be quite the scenario for it to be "accidentally" pulled without the owner's knowledge.) A puzzle without a solution (so far). I'm by no means a lawyer but it sure seems like any modification to the breakaway circuit, that somehow fails or causes the circuit to no work when it's needed, could be a huge liability issue if there's bad consequences.

[TedS]

There seems to be no point installing a fuse rated above the consumed current. That just inserts another element in the circuit. The consumed current will be the same whether accidental, malicious, or emergency activation. Upsize the 16ga to 14 or 12 if the concern is wire heating rather than compromise the emergency braking system.

[Cate&Rob]

When I installed EoH (Electric over Hydraulic) disc brakes on my Reflection 5th wheel, I had a similar concern with the EoH manufacturer showing an unfused circuit for the Breakaway apply. I contacted them and they seemed more concerned with a blown fuse preventing brake apply in a trailer breakaway situation than melting wires in an accidental switch pull. This appears to be a broader system design than just RVIA because it applies to all sorts of trailer brake applications.

Accidentally pulling the breakaway apply is more common than one might think. It can sometimes happen on a tight turning maneuver. A strong diesel tow vehicle may never know that the 1950's technology electric trailer brakes have been applied if the rig is moving at highway speed. I saw the results of this at a Rally where another owner pulled in after towing several hundred miles with the trailer brakes applied. Brake wiring and a few other things were melted . . . a fuse would have probably mitigated this damage at some point.

On my EoH system, I installed an auto resetting circuit breaker. What I considered to be a "compromise" between no circuit protection and a one time fuse.

Rob

[AlexPeterson]

Thanks for the responses - if the manufacturer's concern is about a fuse failing, it might date back to the old in-line glass fuses, which were and still are awful. I'm running a awg 12 to power this circuit, and am putting a 20a blade style fuse in it. I see: (low risk of fuse/circuit failing) X (low probability of actual disconnect event) = really low risk. I do see a higher risk that that wire, out in the elements, could find a path to ground and get toasty. My $.02.

[TedS]

Your choice. You may see improved brake performance with the larger wire. Tie and protect the wire to prevent chafing and the risk of a short. If you install a fuse, routinely inspect it. Out of sight, out of mind may come back to bite.

[AlexPeterson]

Your choice. You may see improved brake performance with the larger wire. Tie and protect the wire to prevent chafing and the risk of a short. If you install a fuse, routinely inspect it. Out of sight, out of mind may come back to bite.

Ted - I hope I don't ever see this "improved brake performance" with the bigger wire since this wire is only for trailer disconnect braking!