Electrical Fire Hazard? - Trailer Brake Wiring

[Luv2Ski]

The duplex jacket wire I think is automotive brake cable.
http://truckpartsetc.com/sales/PDFs/..._WireCable.pdf
Duplex Brake Cable
• Duplex brake cable is made with two polyvinyl chloride (PVC) insulated general purpose primary wires laid parallel and covered with a high quality 30 mil polyvinyl chloride jacket.
• Internal wire is rated for 12V DC and meets S.A.E. J1128 specifications.
• The jacket provides a compact cable and protects the insulated conductors against weather and acid effects.
• Color code: black and white with gray outer jacket.
• Sizes 12 and 10 gauge are recommended for electric brake wire.[Emphasis mine]

Yet Pat said they were 16 ga in post #11 . Yikes! Almost motivates me to take a micrometer out to the storage lot and dig out the brake cable. Free air or not, 16 ga. shouldn't be carrying that much current on a 3-axle rig. Note that per the data sheet in Gene's post above, the resistance per 1000 ft. of brake cable is 4.7 ohms, not the 4.016 ohms I got from my reference. That is even worse conductor performance and it means even less power is delivered to the electromagnets than what I calculated previously.

That brake cable reference lists conductor lengths for a 10% voltage drop so what is the expected voltage drop on a three axle GD 5-er? Again, we assume 80' round trip on their 16 ga wire. That would be 376 milliohms (not 321 as I assumed using my wire reference). Again with 13.5 v battery voltage, 6 paralleled electromagnets @ 533 milliohms, ...the voltage across the electromagnets comes out to 13.5v * 533/(533 + 376) = 7.9v which is 58.6% of the battery voltage. Stated differently, the wiring alone consumed 41.4% of the power in the emergency braking circuit. Only 117.5 watts of energy is available for the electromagnets to split 6 ways.

In addition to this substandard electromagnet power, just add grease-impregnated brake shoes (for those of us with the older GD rigs), steep and winding grades like on Raton Pass, Colorado and it's amazing my family and I didn't end up in a tragedy. Runaway rigs are fairly common here - sometimes with deadly results. This one happened last month on I-70, just a couple of miles from our home. Sadly, four people died and several were seriously injured in a 28-vehicle pile-up (earlier reports understated the number of vehicles).

[Luv2Ski]

Reviving this thread in light of new (to me) information:

Grand Design has recalled certain models of Reflection TT and fifth wheels for what seems to be the problem outlined in this technical thread. That's the good news. Speaking only for myself, I think the bad news is that it doesn't go back in time far enough and the recall scope isn't broad enough. I found the fire hazard problem in our early 2017 328M Momentum.

I'd like to invite Solitude and Momentum owners to check the breakaway switch wiring on their rigs using the picture in post #1 of this thread as a guide - especially those Solitudes and Momentums built between 2014 and 2018 and not modified for EOH disc brakes, solar, etc. Reflection owners not covered by the below recalls may also want to check their wiring too.

Here's the recall link I saw on the FB forum today. The Reflection recalls listed are 18V-764 & 18V-729.

[Flip94ta]

I found this thread via a search and I want to thank you guys for the information you posted. I was surprised when I picked up my new imagine last year and I needed to set my factory controller to 8.5 for a rig with brand new brakes. I have tried adjusting them this past month and now I’m up to 9.5 on the controller but I what I consider too much drag on the brakes.

At the same time I have been working on moving my dual lithium batteries to the pass though and I have noted how the battery and converter wires are all a size too small and replaced much of it. I started to investigate the brake wires. Etrailer recommends 12 gauge or preferably 10ga. Mine is a single 14 gauge pair that runs past the rear axle and then comes forward back to it, it’s then spliced to feed the front axle. I’d estimate they ran over 20’ of the 14 gauge wire. From the frame to the brake assembles it looks like they used 3’ of 16 gauge wire. The front axles wire must of been knicked because they gave it an extra splice along the way to the wheel. SMH.

The crazy part is that the jacketed 14 is long enough to reach the wheel assemblies! I’m not sure why the white 16ga wires were added.

So my question to you guys, I eliminated my 30A thermal breaker that the brake wire was attached to any replaced it with a 1/4” buss bar since I ran larger battery and disconnect cables and put a 70amp breaker just after the battery bank. Do I need to reconsider this and put that single black 16 gauge wire going to the emergency disconnect back on the 30amp breaker?

Next question, I bought some 3M 314 gel filled splices like the factory used and I was going to put two in the junction box and run a parallel 14 gauge wire back to the front axle. I was planning to ground it at towards the tongue using the same lug as the jacketed 14 gauge? Is there a better way? Should I be grounding closer to the axles?

[Flip94ta]

The old setup.


New setup

[Roll With The Changes]

I discovered many of the same issues discussed here while try to sort out the hot side of the battery switch. As I was scratching my head trying to figure out why things were done the way they were, it suddenly became very simple in my mind...

The brake system needs to be completely isolated from any other house wiring. In my mind, applying the brakes in a breakaway situation outweighs any potential over current problem. So by that thinking, there should be a single wire run from the battery through the break away switch to the brake magnets... Minimal splicesand no fuses or breakers. If I find a burned wire on the trailer that has safely stopped after a breakaway, I can live with that.

[gbkims]

So my question to you guys, I eliminated my 30A thermal breaker that the brake wire was attached to any replaced it with a 1/4” buss bar since I ran larger battery and disconnect cables and put a 70amp breaker just after the battery bank. Do I need to reconsider this and put that single black 16 gauge wire going to the emergency disconnect back on the 30amp breaker?

Next question, I bought some 3M 314 gel filled splices like the factory used and I was going to put two in the junction box and run a parallel 14 gauge wire back to the front axle. I was planning to ground it at towards the tongue using the same lug as the jacketed 14 gauge? Is there a better way? Should I be grounding closer to the axles?

Which wire in the photo is the breakaway 16 Awg, green or red arrow?


The brakes per dexter manual, pull about 3 amps per brake at 12V.
For my brakes, from the 14 Awg brake cable, I ran one duplex brake cable to front left brake, a 2nd duplex brake cable to front right brake, then jumpered back to each rear brake.
So a parallel run to the left and right brakes. I'm not using the 16 Awg that runs through the axle tubes.
I paralleled the wires at the front. Didn't ground back at the brakes.

I tested the amps by pulling breakaway switch. With 12.66V at the DC bus, measured 15.36A total for all 4 brake electromagnets.

[Flip94ta]

The red arrow is a 16ga wire that runs up to the break away. I think that 10ga back cable is the 7 pin 12v+.

I appreciate your responses!

I will take that extra long duplex that’s there now and run it over to the curb side and I’ll run my new 14ga down the street side, thanks for the idea. I’m new to trailer wiring so I just want to double check with you guys. Using the pic below I’ll spice two positives off the blue 12ga wire, then two more wires off the black 16ga, both those will meet in my 314 connectors and I’ll splice those two with my 14ga running back to the axles? I plan on running the neutrals off a new lug attracted to one of the 3/8 SM screws next to the junction box. I assume that black wire the breakaway wire?

[gbkims]

The red arrow is a 16ga wire that runs up to the break away. I think that 10ga back cable is the 7 pin 12v+.

I appreciate your responses!

I will take that extra long duplex that’s there now and run it over to the curb side and I’ll run my new 14ga down the street side, thanks for the idea. I’m new to trailer wiring so I just want to double check with you guys. Using the pic below I’ll spice two positives off the blue 12ga wire, then two more wires off the black 16ga, both those will meet in my 314 connectors and I’ll splice those two with my 14ga running back to the axles? I plan on running the neutrals off a new lug attracted to one of the 3/8 SM screws next to the junction box. I assume that black wire the breakaway wire?

Yes that black wire is the other side of the breakaway switch. It puts the TT battery +12V on the brakes when the switch is pulled.
Attached drawing is what I think you'd have for parallel run to left and right side brakes.

[RickLight]

I discovered many of the same issues discussed here while try to sort out the hot side of the battery switch. As I was scratching my head trying to figure out why things were done the way they were, it suddenly became very simple in my mind...

The brake system needs to be completely isolated from any other house wiring. In my mind, applying the brakes in a breakaway situation outweighs any potential over current problem. So by that thinking, there should be a single wire run from the battery through the break away switch to the brake magnets... Minimal splices and no fuses or breakers. If I find a burned wire on the trailer that has safely stopped after a breakaway, I can live with that.

I completely agree with with this sentiment. I work in electrical design, though not an engineer. Much of this discussion has not taken a 'safe engineering' approach. Fuses, splices and such are far more likely to fail than plain wire. The loss of emergency braking is likely to cost innocent travelers their lives, vs a fire that will cost a trailer. NO COMPARISON!

Now the wire size question is another matter. I don't see why GD would short us pennies on a safety issue, especially when it appears that industry standards go against them. Court battles have been lost on just that much!

I challenge a GD representative to present their view in a public forum. Failure to do so has also lost court cases. The question; did GD build a sub-standard safety system in thousands of trailers?

[Flip94ta]

Thanks for the chart, I got the junction box done today and I’ll run the new leg tomorrow. Hoping to hit the road Saturday!!!!