CAST tinned cable

[sitelights]

In July 2004 I requested and received from CAST generous samples (about six feet) of their tinned 10 gauge and 12 gauge two conductor cable. These lengths of cable were sent to me without charge and freight paid. I had a number of Cast fixtures with 25' leads of 16/2 and that is incorporated into the review.

Like my other product reviews I will be comparing similar items from different manufacturers. In a recent post on the "Cable, Wiring & Connectors" Forum I referred to "test results" which is technically incorrect. The correct term is "examine" since I do not have the equipment necessary to measure the dielectric properties of the cable. This review will cover visual and tactile impressions with some personal comments on the topic at hand.

On cursory examination of the unstripped CAST tinned cable and the untinned cable (10/2 and 16/2 sourced from MilSpec Industries in 500' reels) look identical. Each of the samples has shiny black PVC sheathing ribbed on one side to maintain polarity if you choose. Polarity is very important in our installations because we very frequently "loop" our systems (search) and the ribbed side is much more easily identified by touch as opposed to some cable brands that rely on printing or imprinting to differentiate the conductors.

All of these products are UL listed and appropriately marked; as an example the white printing on the CAST 10/2 is almost 8" long: "ELECON - CAST E222386 (UL) 10/2 150v 60 (degrees) C UNDERGROUND LOW ENERGY CIRCUIT CABLE SUNLIGHT RESISTANT". The 12/2 and 16/2 are similarly marked but by debossing rather than printing. My MilSpec samples (no 12 gauge-we don't use it) are visually different if closely examined: printed in blue on both their 10 and 16 gauge product are sequentially numbered footage indicators. These footage numbers are a request from me and done at no upcharge.

When all the cables are stripped it is instantly apparent that the CAST product is tinned and I mean each individual strand and not just a surface coating on the strand bundles. Since it was a slack day I actually counted the individual 30 gauge strands in each wire size : 96, 70 and 18 for the 10, 12 and 16 gauges. This chore was similar to counting the holes in window screening. The count for all the cable sizes was nominally equal.

The conductors all split and stripped about the same. We use Thomas & Betts (T & B) model WT 2000 wire strippers; expensive ($40.00) but worth it since they cut, strip, crimp and have five thread-in bolt cutters 4-40, 6-32, 8-32, 10-32 and 10-24. Using an inferior tool (DIY vs professional quality) for production work is a false economy since it takes longer and is more likely to cut strands when stripping. Sloppy work can easily reduce 10/2 to an effective 12/2 gauge.

I stripped lengths of all the samples and buried them in a wet part of my garden for six months. The copper strands began oxodizing in 24 hours and went to black in a week. The tinned strands stayed shiny and only dulled slightly after 6 months.

These observations say it all: tinned cable is superior to plain copper. At this point it may be revealing to do a site search on "oxidation", "corrosion", "cable life" to get some other opinions. If I seem to contradict myself in some of the posts on this topic it is likely that such a conclusion is justified.

That was the subjective part of the review; now let me get the objective part. Product choice is based on many things and proper weight must be given to the utility aspects of a decision.

The Cast product sheath is too stiff and hard for my uses: the Hadco LVC3 pierce point connectors are difficult to use since, like the Paige product, the sheath is also too tough to readily accept a pierce point connection. In zone 6-7 we are often working in below 50F weather and this exacerbates the problem. The MilSpec cable that we use stays supple in cold weather which makes it easier to lay out; it also has a slightly softer sheath when attaching the LVC3; the 16 gauge fixture leads (CAST, Unique and others) do not fit the LVC3's lead wire slot; the other products are not available with the footage markers and other rationales. It is essentially a trade-off and for our operation the CAST product does not work. Now if CAST made a soft, supple cable with footage markers I would probably change my mind.

There is no point in repeating myself on the topic of oxidation of copper which I consider overblown.

The slight upcharge for tinned cable is a non-issue; copper market prices fluctuate to the extent that the real upcharge is in the rise and fall of raw copper prices over time. If I was just starting out in the low voltage landscape lighting field I would probably come to a different decision on tinned vs plain (and on many more matters I am sure). The tinned product appeals to me for the same reasons we choose not use any ferrous metals in our installations. The tinned cable seems to me to offer a more elegant solution to oxidation and coming from me this is high praise indeed.

[SteveP]

Interesting review. As you correctly state, a few broken strands in a 10/2 cable makes it equivalent to a 12/2. I haven't seen data on this, but imagine if all the cables strands became severely oxidized. This effectively increases the resistance for the outside layer of each strand. Wouldn't this also eventually make a 10/2 equivalent to a 12/2? Also if you needed to resplice a fixture after a year or two, you would be splicing into an oxidized wire, making a substandard connection. It would be interesting to hear from an electrical engineer on this.

[SteveP]

Joe, as an update to your review from a couple years back:

1. Our CAST tin-coated wire now has remaining feet numbered.

2. A wire manufactururer has challenged the superiority of tin-coated wire for landscape lighting (they sent memos to our customers!) so I did an exhaustive search of the literature (up to 50 years back) in engineering, metallurgy and corrosion and consulted with engineers to make sure our claims were based on fact. The results were interesting and pointed to the following:

While tin actually corrodes faster than copper, the tin coating is sacrificial to the copper, so the copper maintains its integrity longer.

The oxidized tin (stannous oxides) maintains good conductivity while oxidized copper (cupric oxides) rapidly loses conductivity. This means that an oxidized copper wire increases in resistance as it ages while tin-coated wire maintains good conductivity.

This loss in conductivity of cupric oxides also makes it nearly impossible to make a good splice or solder junction with old copper wire. Old tin-coated wire can still be re-spliced or re-soldered even after several years.

You can read my article on the subject at www.cast-lighting.com/art-tin-coat.html.

[sitelights]

It is heartening to see a serious topic taken seriously; the many points made on the superiority of tinned vs. untinned are very persuasive. The link to the detailed research on this topic is a must for any professional. It is not possible to make an informed decision without examining alternatives.

Our installations are done with untinned 10/2 gauge cable; this decision is based on our 20 year preference for pierce point connectors and the subsequent absence of splices to maintain the integrity of the cable. This is a topic that I have exhausted in my many posts.

Designer/installers currently relying on "cut and nut" i.e. the use of twist-on wire connectors are urged to adopt a more robust and reliable connection method. No pun intended but they should "mend" their ways. "Cut and solder" if your installation method requires segmentation of the distribution cable; this is one of the two alternative, reliable ways to maintain the integrity of the most important component of the landscape lighting system. The other method, crimped splices with silicone seal is detailed under "Buchanan"; my gut feeling is that the crimp is the best connection. It would be interesting to subject a crimped and a soldered connection to the "pull apart" test; my money is on the crimp.

The cable is subsurface; it cannot be readily examined; it becomes entangled with roots; it is subject to the most harsh conditions; it is the most difficult component to troubleshoot and replace. Throw away those stupid wire nuts and the attendant (and pitiful) electrician's tape; do not rely on gel-filled twist-ons no matter what the hype. This closes the ranting segment of my post.

The addition of footage markers should be a welcomed change for the users of tinned cable since it adds a level of accuracy important to both the designer/installer and the client. With the current skyrocketing of copper prices designing by the foot and charging by the foot aids cost containment for both.

Now, about the hard sheath...