6 awg copper wire

ws9876 · August 2007

hey welding cable used for inverter hook ups is many strands of copper,many. I have some 6 awg I got at Lowes that is about 10-20
copper strands about the size of romex strands. It looks like the examples of copper and aluminum stranded wire that you see on
the solar sites, but ISNT the MANY stranded wire like bulk welding cable, which seems to have 100 or more strands. Is my wire ok for
hooking my inverter to the batteries.??? thanks

icarus · August 2007

Re: 6 awg copper wire

Assuming #6 wire in question meets the spec for the voltage, amperage etc of the system, there should be no problem using stranded wire. Stranded wire is more flexable and easier to use in any give wire gauge. I'll let other experts weigh in whether you need to de-rate stranded wire. I do know that there are some terminal lugs that may not be approved for stranded wire, but it is rare in my experiance.

Icarus

crewzer · August 2007

Re: 6 awg copper wire

WS9876,

Check the labeling on the insulation. If it reads something like this, then you’re probably OK to go: "600 V UL-listed type MTW or THWN-2 or THHN or Gasoline and Oil Resistant II or AWM" This is the type of stranded wire that’s readily available in my local Home Depot stores.

You’re right about “fine” stranded cable being potentially problematic. Fine strands can break easily, and they can also work loose from non-compatible compression fitting lugs. You can read more about this topic in this document from John Wiles. I don’t know if there’s any “official” view on using this type of cable with T&B Blackburn screw-type compression lugs.

Fine stranded wire isn’t always a problem. My battery-to-inverter cables are fine strand “X-Flex”, but I bought them as pre-made assemblies from this vendor. The vendor claims that the wire, the lug, and the crimping tool used to make the cables are all UL-listed.

HTH,
Jim / crewzer

SolarJohn · August 2007

Re: 6 awg copper wire

Wiring IS expensive, but I've found bargains at a local electronic surplus store. If not for that, I might have bought a set of jumber cables to canabalize for battery bank wiring. Terminals are available from automotive supply stores, and I've also located red, white, and black heat-shrinkable tubing to complete the job.

The ends of finely-stranded wire can be tinned (apply solder), to avoid some of the problems stated on this thread.

Anyone making their own cables should make sure to select a wire size that is adequate for the expected current flow. Here's a chart: http://www.powerstream.com/Wire_Size.htm

As previously stated, wire intended for outdoor use needs to meet electrical codes.

John

rplarry · August 2007

Re: 6 awg copper wire

WS
Welding cable and most marine wires are made to be more flexible and are suitable to be used in a non stationary enviornment. The wire you can buy at Lowes and Homedepot are made from heavier copper strands and are not very flexible, ane are meant to be mounted in a stationary enviorment where there is not very much vibration. So if your inverter is mounted to a wall or something then the wire from Lowes will be just fine. Just make sure that #6 will handle the amps that your inverter will draw from your batteries.
Larry

crewzer · August 2007

Re: 6 awg copper wire

All,

Trying to tread gently here…

I’ve no doubt that a few / some / most /all of us have taken a few “short cuts” here and there when experimenting with and building various systems. I’ll be the first to admit that I have. However, I recommend that we all use considerable care when using non UL-listed tools, cable, lugs, circuit breakers, etc. I’m sure many of you will remember our lively discussion re AC vs. DC ratings for circuit breakers.

Further, I recommend that we use even greater caution before suggesting that others use non UL-listed items for PV energy system applications. This includes items that are UL-listed for their intended applications, but not for PV systems. Examples include many AC rated breakers, which are generally not listed for DC use, and automotive and marine cable, connectors, fuses, and other components. Many of these items are not UL-listed at all, and those that are listed are usually for that intended use and not for PV system use.

John Wiles, arguably the U.S. guru on PV systems and the NEC, has written extensively on this issue. See here for a list of Wiles’ articles, i.e., “Code Corner”: http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/Codes-Stds.html

I agree that many of the items discussed are not inexpensive. However, it’s my view that their initial cost is a fair investment in their associated safety. By taking short-cuts, we and/or some of our less-technically inclined visitors may make costly and/or dangerous mistakes.

Thanks all,
Jim / crewzer

SolarJohn · August 2007

Re: 6 awg copper wire

Jim,

I agree with your comment: "I recommend that we all use considerable care when using non UL-listed tools, cable, lugs, circuit breakers, etc." wholeheartedly, and that those items need to be used properly. However, I wouldn't want anyone to get the idea that just because an item is UL-listed, and used for it's intended application, that it's safe. An 18 guage wire will heat up and cause a fire if you try to push 20 amps through it, whether it's UL-listed or not.

A course in basic electronics should be a prerequisite for anyone who builds their own system, and that should be followed by a course on batteries (for those who will be using them).

A genuine concern for the safety of others is just one of the things that make this forum great. Keep up the good work!

John

crewzer · August 2007

Re: 6 awg copper wire

John,

I’m glad that you’re in general agreement with my recommendations. However, I’m having difficulty with this rationale:

However, I wouldn't want anyone to get the idea that just because an item is UL-listed, and used for it's intended application, that it's safe. An 18 guage wire will heat up and cause a fire if you try to push 20 amps through it, whether it's UL-listed or not.

I would say that using UL-listed items for their intended applications is and should be considered safe practice. 20 A though 18 AWG wire, which is rated at 18 A max current per NEC 310-17, is neither a good idea nor safe, as you suggest. But, 18 AWG cable isn’t intended for that application.

HTH,
Jim / crewzer

mike95490 · August 2007

Re: 6 awg copper wire

Sometimes, as wire ages, the copper oxidizes. My 40yr old 10ga house wire, is about 10% nasty black oxide. I think it's still safe, and wire nuts bite well, but if it was 10ga of fine strands, there would be nothing conductive left. The finer the strands, the more surface area to corrode with the air, even inside the insulation, enough oxygen makes its way in.

ws9876 · August 2007

Re: 6 awg copper wire

just to know ,its for a 300 watt sure sine and is going in a car for now, and I am not buying any more wire. this will have to work, stiff or not.;)

crewzer · August 2007

Re: 6 awg copper wire

Perhaps your wire is something like this, with 19 strands. Morningstar recommends a minimum of #6 wire for the battery connections to the SureSine.

Good Luck!
Jim / crewzer

6 awg copper wire

Comments

Categories