Tinned Copper (TCCW)

Just an example of the problem associated with this type of conductor…



Hi Jeff, I have seen plenty of this in the field, but also some that is still very pliable. Also I have cut back the jacket and the wire is usually, what I would call… fine. It seems that this deteriorates from being outside the original jacket. My questions are , is this always called out in an inspection, or made aware of. I suppose it should be. Also, do you know if tinned copper was used with any other type of insulation. The reason being is that tinned copper is not the problem, its the insulation covering it. Thanks.

I always indicate the type of wiring in the report - AL, CU, TCCW, K&T, etc.

I too have seen TCCW in very good condition. The problem (IMHO) is that the majority of it is concealed and cannot be inspected. We can assume that it’s in relatively decent condition because it has been “protected” within conduit for so many years, but we have no way of verifying this.

The tin-coating is intended to protect the rubber insulation from the deteriorating effects of the copper conductor. However, as you indicated, the rubber will begin to deteriorate once the cloth covering has been removed or damaged.

We (as inspectors) have no way of knowing whether there has been any damage to the cloth-sheathing when the conductors were pulled through the conduit, so I think it’s prudent to recommend “further evaluation” (even though I hate that recommendation) of the TCCW by a qualified electrician.

Interesting conclusion Jeff. Not that it’s up to us to determine how that is to be done…but what do you think the contractor will be able to do to evaluate hidden wiring? Would he need to remove the drywall/finished coverings to evaluate what is not readily accessible? Looking at it from a consumes perspective what I read is *my wiring may be unsafe and I should probably replace anyway. *

In the end we can only report on what is readily accessible so there’s always a potential for hidden defects in every component. But I get your point here. You can see some of the wiring visible at the service equipment and it’s not in good condition so…

If I hired an electrician to evaluate the condition of the wiring, I would expect them to check it at junction boxes, outlets and any other relatively-accessible points.

I think most of the real damage occurs over the years when the wiring is “disturbed” by replacing components such as outlets, switches, panels, etc., so checking these points should give a pretty good indication of the integrity of the wiring.

I only flag tinned copper wire for evaluation/repair when there are signs of a problem, like in the original post photos.

However tinned copper wire (like any really old wire) can become a fire/shock hazard if disturbed due to the potentially brittle insulation, and clients should budget for future repairs/replacement.

Also tinned copper is not always in armored cable … it’s sometimes present in sheathed cable, although not as common.

JMO & 2 Nickels

Generally speaking, the presence of tin or rubber insulation are deficiencies in their own right. I recommend mentioning it. How each inspector chooses to handle it is going to depend on that inspector’s style.

There are some things that may have been acceptable at the time of installation but were later determined to be a problem. Tin and rubber are among those things. It that respect, they are much like the problem with aluminum branch circuit wiring.

Early on, tin coating of conductors was popular and soldering was the most common method of making electrical power circuit connections. Solder contains mostly tin and lead. Both have relatively low melting temperatures. The electrical industry started to move away from the use of tin because of the problems associated with it. Electricians continued to make connections with solder but other materials, such as silver, were added to raise the melting temperatures. Silver solder is still very common but not in residential wiring. It is used often in high-temperature applications in conjunction with glass insulated conductors.

It is not practical for an electrician to attempt to evaluate the wiring. The only practical thing to do is to replace it. The problem is not only with the tin. Rubber made 50 years ago is very different from what we now call rubber. Under the best of circumstances, it loses it effectiveness as an insulator. In order to be effective, an insulation has to maintain its dialectic strength. It is not possible to measure dialectic strength visually or with a thermal imaging camera. At a minimum a megger would be required. The insulation has to be tested at a Voltage as close as possible to the insulation’s rating. That means the person doing the testing needs to be able to determine the rating. Today, insulation is always continuously marked but rubber insulation wasn’t usually marked. Even if it had been marked, the markings are not likely to be visible anymore.

Therefore, the presence of either tin or rubber insulation constitutes a deficiency regardless of visible appearance.

I might add something here since after all…I am here ( which is rare these days ). I did a study a few years back on tinned copper and it’s condition in existing dwelling usage. We had an older home that had this wiring in the older cloth style NM Cable and as they pulled down the walls we looked at termination points versus in the wall installations. nearly 100% of all wiring in the walls when we opened up the NM Cables showed no signs of cracking or breakdown interesting enough…however at the termination points and within panel enclosures the cracking and breakdown was wide spread.

As in the images shown by Mr. Pope, typically the radial bends add to the breakdown at termination point over time where excessive heat can be located. It appears that being within the jacket within walls lead to hardly no breakdown of the rubber insulation even with some 60-70 year spans.

Was this a scientific study…well no…but what it told me is that cables that are installed properly ( which we can’t really tell as HI’s or Electricians unless we open up the walls) within walls tend to remain in relative good shape and are protected by proximity to it’s covering. So while I don’t like Tinned Coppers insulation…when left alone, within its covering it tends to remain fine ( in my un-scientific study…lol ) but once outside of it’s covering (much like K & T ) it breaks down.

Just figured you all might like hearing that…I need to look for that study I did as it was on an old computer that crashed a few years ago but I might have saved it.

I find them regularly as well Jeff.

oh Duffy…you ole’ Tinned Copper hater…lol

By the look of the breakers, she maybe a Zinsco Clarita—:stuck_out_tongue:

Hi Paul...me no hate anything, just recommend upgrading it, if they want to fine, if not, install additional Smoke Detectors---:cool:

How about just recommending it be evaluated by a licensed electrical contractor and letting them determine if it needs to be replaced. Or better yet, recommend they install AFCI’s on the circuits and smoke detectors. I always recommend AFCI’s and GFCI’s on older circuits ( again provided it is not some old multi-wire circuit and they have a panel that will allow AFCI’s to be installed…lol )

Just pickin on ya fella…I know you ain’t no hater !

I don’t ever recommend anyone have anyone else evaluate anything, if they don’t like my opinion, they can get other opinions of course, it says that at the beginning of my reports----:lol:

I say I recommend it be upgraded, repaired, or replaced, depending on the situation, but never recommend anyone else look at it…just fix it–:wink:

If another person says its fine…great—its their problem, not mine—:stuck_out_tongue:

Just pickin on ya Paul…long time since I’ve heard from you, must be as busy as me----:smiley:

You know…if it works…Work it…:slight_smile:

yeah…I don’t come around much anymore…busy doing the municipal thing but might be going home soon…looking to take a job as the electrical instructor at a local college so who knows…depends on how I feel tomorrow…lol

Hey Paul … From my experience I agree that the first signs of a problem with tinned copper wire is likely to be where the outer cover has been removed, like in the panel.

Good eye Dale. You are correct :cool: