Doubling Wire Run

[MarkK]

How would you go about doing this as in which connectors would you use and any other considerations? 

I have a run of 12 AWG and instead of buying something heavier wondered if I can take another same length section of 12 AWG wire and combine them? Of course on either end I would have to combine Them to a short section of say 8 or 10 AWG to go to the controller or panel. The wire is SJOOW wire so already has a protective casing and I could use zip ties to hold together.

 

[Zil]

The current would flow with higher amps through the wire with least resistance. Depending on the draw. If many amps it could create a problem with melting insulation or even fire. Every given length of any gauge wire will have a different resistance. That is the nature of wire. When all the strands are bound together this is minimized. 12 AWG is only safe for about 40 amps before overheating.

 

[John61CT]

Doubling is fine, certainly better than leaving it one undersized

**as long as**

same gauge, length

solid well crimped terminations.

One big wire better though.

 

[Zil]

Doubling will work, until it fails. Don't class it as fine.

 

[Spaceman Spiff]

 . . . wondered if I can take another same length section of 12 AWG wire and combine them?  . . .

Use the correct wire for the job.

I would only use the multiple wires in an emergency and then only with each wire having the proper fuse protecting them.  For 12 AWG stranded wire you would need to have a separate 20 amp fuse on each wire.

 -- Spiff

 

[VanKitten]

The electricity will follow the path of least resistance. But...leave the other on used.

If you need 30 amps....do not think that wire gauge for 15 amp will work if you double it.
It will fail in just exactly the same way that only one wire would. Because the electricity will follow one path till it shorts then the other till it shorts.

No..use the correct gauge wire.

 

[deadwood]

I agree with everyone else. Use the proper wire or don't do it. It's not a case of if it will fail but more like when it will fail. Electrical isn't the place to take shortcuts. If anything I would over size the wire just for extra precaution.

 

[MarkK]

Well then, might as well close this thread. Thanks all. Good stuff here.

 

[GotSmart]

I look at it as cheap fire insurance.  One payment only.  

 

[sephson]

The electricity will follow the path of least resistance.

This is actually partially incorrect. Electricity does not just take the path of least resistance, it follows all available paths.

That said, I agree with your conclusion. This actually makes doubling up the wires more dangerous, not less.

 

[Ticklebellly]

Doubling is fine and works well particularly if making do with what you have. Current flow in either wire will be a function of voltage over resistance in that wire run. If exactly identical wire size, the current in each wire will be close enough to identical (Ohm's Law) while the parallel arrangement will provide double the current carrying capability. Current does not choose to exclusively run in the wire with least resistance. Many a welder earth wire has been made using three or four parallel runs of three core flex.

The pinch point in these kinds of arrangements is still the crimp and the attachment to the terminal.

 

[Ticklebellly]

....even if wire was available in a large enough cross section to carry those amps it would be very difficult to work with.

That's what Buss bars were invented for.   Once saw a spanner dropped across Buss Bar arrangement that averaged 2500 Amps at 50 Volts (old tech Step-by-Step Telephone exchange).   Spanner transmogrified into a big blue flash and left a couple of singe marks on the Buss.

 

[Ticklebellly]

Them to a short section of say 8 or 10 AWG to go to the controller or panel. 

Don't like that.   Crimped terminals on either end and then stacked on the controller terminal post will give the better connection with least resistance.   Got an IR thermometer or FLIR?   Great way to check for hot joints.  IR thermometers are just a few $ and FLIR attachments for a smart phone are close to $200, but useful for lots of applications.

Worried about the conflicting opinions here?   Get an electrical engineer to do a Nodal Analysis to chart voltage at nodes and current in wire runs, if you need independent input to work things out.

 

[GotSmart]

You are only dealing with a simple 12 volt system. Don't overthink everything. Just use larger wires with the proper fuse.

 

[Scott7022]

Going back and forth sounds confusing and while what most are saying is correct in the end, how the express it looks to be yes you can no you can't answers. So use this link, it is free and you will have THE answer without reading debates on physics. No one gets frustrated and says shut the front door or anything.

http://circuitwizard.bluesea.com/#


Blue sea is the marine standard. The only thing scarier than an electrical fire in a van is an electrical fire on a boat. They have all sorts of free resources and great tech tips written by Marine Electrical Engineers and you don't have to buy their products. I do because I see it as insurance as well. Pay once and have it work.

I was watching a guys video the other day..Bug out van or something. He was always going on about doing it cheap. Then in one of his other videos about motocross he goes on a rant for twenty minutes about cheap an china crap and blah bah as this quit working and he cheated out on tires and it just about killed him. Cheap is wrong, inexpensive is fine, and buying the most expensive won't always be correct. But in life you usually get what you pay for. Everyone has an opinion, it is the very talented that get paid for them.

Use the link YOU have to be certain as YOUR life depends on it.

 

[John61CT]

By reading the forums over a longer period of time you educate yourself, not only from vendor info but also those with professional long-term real-world experience over thousands of installs.

You also get to learn who to listen to and who just give opinions without much real knowledge.

Fact is if done properly nothing wrong with it, certainly not "dangerous", especially when done only to reduce voltage drop while the single run is sufficient for heat issues at that ampacity.

But it is a cost-saving workaround and as I said above, not ideal.

Your rig your call.

 

[Scott7022]

---

Yes totally agree with the fact as you pointed out. The issue is everyone is giving suggestions based on assumptions.

Fact is we don't know how long the OP's "run of wire is"
Fact 2 we don't know how many amps he is directing into this unknown "run of wire."
Fact 3 we don't know the voltage. Sure it is probably 12 volt and he doesn't have an H1 running 24volt. It could be AC...
Fact 4 we are assuming it is connected and currently working. Perhaps he ran the wire and hasn't connected it to his dual battery system with a group 31 in the engine and a golf cart six volt in the back of his 30 foot class A. Should be good the voltage drop will help to not overcharge the six volt. Believe me I have seen some stupid set ups and while it is cool we are giving the OP the benefit of being smart. You don't actually know.  

I get we are all trying to be helpful. But we need to know what ALL the FACTS are before making recommendations based on assumptions.  

Hence my direction to find an answer based on the above unknown facts. Go to the free wire recommendation guide and look. It CHEAP!

 

[MarkK]

---

Yes totally agree with the fact as you pointed out. The issue is everyone is giving suggestions based on assumptions.

Fact is we don't know how long the OP's "run of wire is"

25'

Fact 2 we don't know how many amps he is directing into this unknown "run of wire."

9 amps

Fact 3 we don't know the voltage. Sure it is probably 12 volt and he doesn't have an H1 running 24volt. It could be AC...

12

Fact 4 we are assuming it is connected and currently working. Perhaps he ran the wire and hasn't connected it to his dual battery system with a group 31 in the engine and a golf cart six volt in the back of his 30 foot class A. Should be good the voltage drop will help to not overcharge the six volt.

Smart being relative, I am not when it comes to electrical. Connection is directly to 2 Lifeline grp 31 agm's.

---

Lesson learned, and my first reply still stands. Should have bought better wire than the 12 awg. Didn't know about "doubling the run" which, well, I would think would be part of the online calculators, but nope, so lesson learned.

Now on to trying to determine connection methods.

 

[John61CT]

Better to spell out all the details, make plan drawings, use the calculator (Blue Sea's app is great), ask questions, all before spending money or actually installing anything.

 

[Scott7022]

Using the blue sea Calculator we see that 12 volts at 9 amps over 25 feet is ok with 12 gauge both for amps and 3% voltage drop No doubling required . So you answered your own question. Doubling isn't shown as isn't preferred method for reasons already pointed out. Doubling starts to happen with big length runs and/or huge amps. Rarely seen in our applications. Four Ought cable in my run was stupid big.

Smart and stupid are always relative to the subject matter. I didn't mean to offend, and if I did I apologize. My point was people assuming someones ability at a skill set. In this case wiring. So if you are coming directly off the battery and drawing 9 amps make sure you splice in a 10 or 15 amp fuse with 12 gauge or slightly larger wire as close to the battery as you can. Ideally within 9 inches.