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10-20-2021, 09:59 AM
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#1
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Wiring electric tongue jack on trailer with DC-DC charger
Electrical question for the group on optimal wiring of new electric tongue jack. Since I have a modified system with a Victron DC-DC charger on the tow vehicle charge line I can't simply land on the 12V positive in the 7-pin junction box. If I did the jack would only be powered when plugged into the tow vehicle with ignition on. Since my battery is in the passenger side dinette all the feasible locations are inside the trailer. See attached.
Option 1: Route positive to terminal on the 40A thermal breaker I installed on the charge line. Provides circuit protection if integral auto reset circuit breaker integral to jack malfunctions.
Option 2: Route it directly to the terminal on the battery disconnect switch. Relies on the integral auto reset CB for protection. Could also add my own inline fuse I suppose.
Option 3: Route it to one of the open 30A fuse positions in the power center.
All options are behind the battery disconnect switch so it would provide some added security I suppose that one could throw the inside switch and the jack would be inoperable.
Any thoughts on the best location to land would be appreciated.
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10-20-2021, 11:38 AM
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#2
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Senior Member
Join Date: Feb 2010
Location: Oswego, New York
Trailer: 2017 Escape 21C, 2018 Ford F150
Posts: 5,377
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I think any of the options would work as long as you fuse to protect the wire (and use adequate wire size for the tongue jack draw.
Speaking (well, typing) of fusing, I would not be comfortable with the #10 wire on an 80 amp fuse used for your run to the breakaway switch. I'd either increase the wire size or fuse it at 30 amps to protect the wire. The magnets draw 6-8 amps per axle, so 30 amps should cover the full draw emergency breaking would pull. Some recommend no fuses & wiring directly to the batteries, however the current draw with a fault could be 100's of amps, melting anything but the largest wire.
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10-20-2021, 12:04 PM
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#3
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Quote:
Originally Posted by Vermilye
I think any of the options would work as long as you fuse to protect the wire (and use adequate wire size for the tongue jack draw.
Speaking (well, typing) of fusing, I would not be comfortable with the #10 wire on an 80 amp fuse used for your run to the breakaway switch. I'd either increase the wire size or fuse it at 30 amps to protect the wire. The magnets draw 6-8 amps per axle, so 30 amps should cover the full draw emergency breaking would pull. Some recommend no fuses & wiring directly to the batteries, however the current draw with a fault could be 100's of amps, melting anything but the largest wire.
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Thanks Jon. It's a 60A fuse near the battery but your point is taken. Escape originally had the breakaway wired in to the tow vehicle charge line which intersected with undersized main wiring from onboard battery with no fusing. When I did wiring upgrades Brian B-P had commented on the breakaway wiring. He seemed to recommend straight to the battery which would bypass my added 60A fuse. Oliver does it that way per their wiring diagram. Don't really like the idea of melting wires though if there is a fault. I'll look into fusing that line at 30A as you suggested.
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10-20-2021, 12:19 PM
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#4
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Senior Member
Join Date: Feb 2010
Location: Oswego, New York
Trailer: 2017 Escape 21C, 2018 Ford F150
Posts: 5,377
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Fusing the breakaway wiring is a tough decision. Open circuit faults often are caused by fuse holders & connections. Eliminating them improves safety as far as having the breakaway switch doing its job, but unprotected or under protected wire is also a safety issue. At least in the 19 it is a short run, unlike a run the full length of the trailer run as in the 21C or 5th wheel. If it was me, I'd increase the wire size so that the fuse would protect it.
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10-20-2021, 12:44 PM
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#5
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Quote:
Originally Posted by Vermilye
If it was me, I'd increase the wire size so that the fuse would protect it.
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Jon: Please expand on this thought. Are you suggesting to increase the wire size all the way to the brakes themselves so my main 60A fuse near the battery protects the entire wire run?
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10-20-2021, 01:22 PM
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#6
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Senior Member
Join Date: Feb 2010
Location: Oswego, New York
Trailer: 2017 Escape 21C, 2018 Ford F150
Posts: 5,377
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Quote:
Originally Posted by rubicon327
Jon: Please expand on this thought. Are you suggesting to increase the wire size all the way to the brakes themselves so my main 60A fuse near the battery protects the entire wire run?
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No, I'd just increase the run to the switch. While the trailer's brake wiring is undersized, it is outside the trailer. I would prefer any melted insulation too be outside...
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10-20-2021, 01:30 PM
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#7
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Senior Member
Join Date: Feb 2020
Location: East of Austin, Texas
Trailer: 2021 Escape 5.0 / 2022 F150 SuperCab
Posts: 2,936
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I'm with Jon insofar as the jack .... any of the arrangements will do the job with adequate wire gauge with a fuse or breaker at the supply-end appropriate to the wire ampacity (obviously the breaker in the jack does not protect the power-supply wire). I'd just go with whichever is most convenient to install.
On the breakaway brakes, yeah, I've seen the pros and con discussions. Though my latest schematic shows a 30A auto-reset thermal breaker on that 10AWG wire, I'm very inclined to change that to a 30A fuse. Here's my thinking (and I welcome comment): - Running with no fuse/breaker on that 10AWG wire is not acceptable to me due to risk of fire if there's a wire fault for whatever reason at any time (that can happen totally independent of breakaway activation)
- IF a thermal breaker trips during an actual breakaway event it will not reset timely to try to help during that short-duration breakaway event (so that behavior would be equivalent to blowing a fuse)
- IF for whatever reason there's a fault to ground in that wire at any time an auto-reset breaker will hopefully trip but will then continue to reset and allow current flow until it trips again, perhaps causing a fire in those repeated attempts (no, I am not a fan of auto reset beakers for this reason). A fuse will hopefully blow before starting a fire if that happens and that's that - the blown fuse prompts investigation of the fault.
Obviously any wire/fire protection device if tripped and undetected is a problem / risk. We should all be doing a breakaway test before each day's towing to try to reduce that particular risk.
Another 'assist' would be wiring an LED indicator across a fuse such that the indicator lights only when the fuse is blown. Many fuse panels have such but it's not obvious unless looking at the panel. It'd be easy to wire a remote bright led in a prominently visible location, and it would not be a 'nuisance' since it would only illuminate if that critical fuse is blown for whatever reason. That indicator with a 30A fuse might provide the 'ultimate' in breakaway security and fire-risk reduction.
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10-20-2021, 08:23 PM
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#8
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Quote:
Originally Posted by Vermilye
No, I'd just increase the run to the switch. While the trailer's brake wiring is undersized, it is outside the trailer. I would prefer any melted insulation too be outside...
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Ok so a 6 AWG wire out to the breakaway switch. Without terminals how do I connect the 6 AWG wire with the light gauge wire at the switch?
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10-20-2021, 11:15 PM
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#9
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Senior Member
Join Date: Dec 2012
Location: Edmonton, Alberta
Trailer: 1979 Boler B1700
Posts: 14,935
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I understand the logic of the heavy wire, but this would likely be the only trailer in the world with 6 AWG wiring to electric brakes... right? It seems like there should be a better solution, whether that is accepting the risk of a failure without overcurrent protection (normal but understandably disconcerting), or adding overcurrent protection which incurs a risk that the breakaway system will not be operable when needed
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10-20-2021, 11:19 PM
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#10
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Senior Member
Join Date: Dec 2012
Location: Edmonton, Alberta
Trailer: 1979 Boler B1700
Posts: 14,935
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Quote:
Originally Posted by rubicon327
Without terminals how do I connect the 6 AWG wire with the light gauge wire at the switch?
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A crimp-on closed-end connector (or "wire nut" or "pigtail connector") can accommodate two conductors of substantially dissimilar gauges.
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10-21-2021, 09:54 AM
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#11
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Quote:
Originally Posted by Brian B-P
I understand the logic of the heavy wire, but this would likely be the only trailer in the world with 6 AWG wiring to electric brakes... right? It seems like there should be a better solution, whether that is accepting the risk of a failure without overcurrent protection (normal but understandably disconcerting), or adding overcurrent protection which incurs a risk that the breakaway system will not be operable when needed
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Just out to the breakaway switch. But I still think it is overly conservative and will likely either just leave it as-is or consider a fuse on the branch wire. Although you implied in my wiring upgrade thread that direct to the battery with no fuse seemed to be an accepted standard. Is that still your recommendation?
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10-21-2021, 10:01 AM
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#12
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Quote:
Originally Posted by Centex
...with a fuse or breaker at the supply-end appropriate to the wire ampacity (obviously the breaker in the jack does not protect the power-supply wire).
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Alan: Why not?
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10-21-2021, 10:31 AM
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#13
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Senior Member
Join Date: Feb 2010
Location: Oswego, New York
Trailer: 2017 Escape 21C, 2018 Ford F150
Posts: 5,377
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Quote:
Originally Posted by rubicon327
Alan: Why not?
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Because a typical fault would be the hot wire wearing through the insulation & shorting to the jack or trailer frame. Since this is before the breaker in the jack, the breaker would not trip.
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10-21-2021, 10:35 AM
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#14
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Senior Member
Join Date: Mar 2016
Location: Burlington Twp., New Jersey
Trailer: 2010 Escape 19
Posts: 7,146
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Quote:
Originally Posted by Vermilye
Because a typical fault would be the hot wire wearing through the insulation & shorting to the jack or trailer frame. Since this is before the breaker in the jack, the breaker would not trip.
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Got it. Etrailer installation video threw me off as they specifically say you don't need to install a fuse due to the integral breaker. Bulldog installation instructions don't mention it either. Incorrect / incomplete advice on their part.
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10-21-2021, 10:42 AM
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#15
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Senior Member
Join Date: Feb 2020
Location: East of Austin, Texas
Trailer: 2021 Escape 5.0 / 2022 F150 SuperCab
Posts: 2,936
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Quote:
Originally Posted by Vermilye
Because a typical fault would be the hot wire wearing through the insulation & shorting to the jack or trailer frame. Since this is before the breaker in the jack, the breaker would not trip.
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Thanks, Jon
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10-21-2021, 04:35 PM
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#16
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Senior Member
Join Date: Mar 2016
Location: New Mexico, New Mexico
Trailer: 2017 E19
Posts: 617
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Sorry to jump in late with a question...
When I redid the battery wiring last summer (solar, DC-DC converter, LiFePO4 battery, etc.) I considered fusing the emergency breakaway switch (but didn't). I noted that the breakaway switch wiring is 14 awg, the trailer brake wiring is also 14 awg. At 3.4 amps per brake x4 would require 14 amps for the trailer brakes. So I figured for the 14 awg wire, it was ok. The only hanging consideration was "to fuse or not to fuse". An ATC fuse would protect the wiring but reduce reliability (any added function reduced reliability). From this stream, it appears the consensus is that a fuse on the emergency breakaway line is prudent?
thanks
edit - if fused what size since load is close to wire rating?
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10-21-2021, 05:19 PM
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#17
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Senior Member
Join Date: Dec 2012
Location: Edmonton, Alberta
Trailer: 1979 Boler B1700
Posts: 14,935
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Quote:
Originally Posted by rubicon327
... Although you implied in my wiring upgrade thread that direct to the battery with no fuse seemed to be an accepted standard. Is that still your recommendation?
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That's what seems to be standard practice, and it is what I have, and I have not changed it because I accept the small risk as reasonable compared to alternatives. I just share information about technology and existing practices; it's your decision and I'm sure that whatever you choose will be suitable.
If the breakaway system is supplied through a fuse, and that fuse is not monitored, then a regular test of the system would seem to me to be particularly appropriate (and is widely recommended anyway, although doubt that many people do it).
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10-21-2021, 06:57 PM
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#18
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Senior Member
Join Date: Mar 2016
Location: New Mexico, New Mexico
Trailer: 2017 E19
Posts: 617
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That was my initial thought, but without a fuse, the wire becomes a fuse if the wire shorts to trailer frame. This becomes a decision of which failure mod is most likely.....
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10-22-2021, 06:05 PM
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#19
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Senior Member
Join Date: Dec 2012
Location: Edmonton, Alberta
Trailer: 1979 Boler B1700
Posts: 14,935
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Quote:
Originally Posted by MVA
... I noted that the breakaway switch wiring is 14 awg, the trailer brake wiring is also 14 awg. At 3.4 amps per brake x4 would require 14 amps for the trailer brakes. So I figured for the 14 awg wire, it was ok.
... if fused what size since load is close to wire rating?
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The 4 x 3.4 amps is a worst case of breakaway operation, and won't occur when the controller is connected unless the controller gain is set to maximum and braking at a full one "g" deceleration occurs. I don't see any concern with simply fusing at whatever you consider safe for 14 gauge wire (perhaps 15 amps).
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10-23-2021, 07:27 AM
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#20
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Senior Member
Join Date: Nov 2015
Location: Baytown, Texas
Trailer: 2017 21' Escape - upgraded version
Posts: 2,697
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Quote:
Originally Posted by rubicon327
Thanks Jon. It's a 60A fuse near the battery but your point is taken. Escape originally had the breakaway wired in to the tow vehicle charge line which intersected with undersized main wiring from onboard battery with no fusing. When I did wiring upgrades Brian B-P had commented on the breakaway wiring. He seemed to recommend straight to the battery which would bypass my added 60A fuse. Oliver does it that way per their wiring diagram. Don't really like the idea of melting wires though if there is a fault. I'll look into fusing that line at 30A as you suggested.
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The 60 amp fuse is fine. The only way that it would blow from the emergency brake circuit is that the wiring shorted to ground and the 60 amp fuse will prevent any wire meltdown.
If you are curious, attach a 10 ga wire to a 60 amp fuse and dead short it across the 12v battery. The fuse will blow before the wire even gets warm.
Using an additional fuse in the emergency brake circuit is not recommended. The emergency brake circuit is a safety system and should be designed for maximum reliability. Also, any failure of the power to the circuit should be readily detectible - blowing the battery 60 amp fuse will leave the trailer 12v dead and about as noticable as it can get outside adding a alarm horn that would sound when the fuse blows. ( idea for a new mod.)
I would suggest adding the trailer power jack to the 10 ga for the emergency brake circuit at the 7 pin junction box with a inline 30 amp fuse on the power to the jack. The two circuits are never used at the same time so it should be fine.
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Engineers believe in fixing it so that it never breaks.
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