4lorn or anyone else.
I ofetn run into corrosion in laod centers. Sometimes, it is enough to have caused obvious over heating (e,g,, melted insulation – see, e.g., IMG_2863.jpg)) but sometimes there is no visual evidence of that.
There are degrees of corrosion, of course, and I’m interested in what experienced folks think.
I’ve posted 2 additional pics (both large for the best details)
Any observations would be welcomed.
The Big Beautiful Bill could do away with much of the Inflation Reduction Act, including the 25C, 25D and 45L tax credits.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
Looks like high humidity---Wet basement.
Thanks.What I'm mainly wondering about is "at what point does 'minor' corrosion at the connections indicate (i) needed repairs/corrections and (ii) at what point should I shut off power to the circuit or system.Whenever I see clear evidence of overheating; bubbled insulation or heat discoloration (usually I see both) I turn off the circuit or system - I will not leave a house with what I believe could be an immediate fire hazard.It is far more common to see some "minor" corrosion with no visible evidence of over-heating. As a generalist, I always recommend that such systems be checked by an electrician, of course, but I always seek other, expert views as to the amount of emphasis I should put on such situations.BTW, do you have any idea of why I sometimes see one just breaker with corrosion, in a box with no other evidence of moisture problem?Could it be a bad breaker? Or perhaps the breaker got wet (sweated on?) at the time of installation?
View Image
Sojourners: Christians for Justice and Peace
Bob, this isn't the question you asked but I suspect the corrosion in the pic where the mains are attached is due to rain water, or condensation running in through the conduit. The inspector had me drill a couple of 1/8 holes in the bototm of the L-box outside of the house to allow any water to escape, rather than running down the cables and into the house. I used electrical putty at the top of the mast, the meter box and panel to try to reduce condensation. To prevent rusting, we can't mount our panels on concrete or wood any more, its gotta be drywall. Hydro now charges about 250 (cdn) to kill a service, so like you I suspect allot of these problems are just left because of the cost ...
The first pix is probably overheating more due to the LH connection having not been properly tightened originally rather than corrosion - even a good 4/0 Al connection can usually be give a half turn easily after the first year, but probably very few ever have anybody go back and retorque, very few likely ever get torqued other than 'by feel' to start with. In own house, open and retorque the 4/o sevr. ent Al wires every 5 years along with the 1/0 Al to subpanels.
The first pix shows rust on the panel itself, the second and 3rd pix show no corrosion other than the terminal and no evidence of overheating. So, likely no heating but condensation from aforementioned wet/humid basement and slightly couple from Cu to termina plating.
It's hard to know just when corrective action is required. I have used an infrared camera to scan panels and been surprised to find that the worst looking connections[corrosion]were cool while others were probably loose and were running at a higher temperature. My feeling is that if this panel and breaker connections were to be depended upon, they need to be cleaned with a wire brush and reinstalled with the liberal use of an antioxidant compound. I like Noalox by Ideal for aluminum and Kopr-Shield by Thomas and Betts for copper wire.
for 'all', but I'm interested in your opinion -
when the various boxes on the farm get opened, I'll check for tightness of the the connections - often will get another fraction of a turn - is there any reason not to spray the clamps with WD-40 so as to reduce the probability of corrosion and keep the threads loose?
Bob, I see no evidence of any compound on the AL entrance wires - thinking that might be one reason for the heat - is the copper entrance pict anywhere near where the water softener is loaded? - - looks like more than water at work to me....
"there's enough for everyone"
I know of no reason that would'nt be OK. I have used a similar product sold by the electrical wholesale houses for the same purpose. It was a "spray lubricant" manufactured by a company that also sold electrical trade specific products, such as contact cleaners, sealers, and coatings. For my money, WD-40 was the same thing as the CRC spray. That is, a very light oily spray that would displace moisture.
Another example, slightly out of focus ....
I am near the Pacific coast north of San Francisco. Meter main corrosion is a major problem. Boxes that are fully exposed to weather show rust in a year.
I insulated the exterior of my box with rigid foam & painted plywood, installed a small electric damp-chaser (25w heating element), and a zinc anode used on boats. In addition, all connections are coated with a conductive corrosion inhibitor made by Hubbel that the power company uses. The meter is installed in a concrete block pedestal with a roof that also helps a lot.
It appears to be holding up better than other meters of the same age but time will tell.
Like someone else said, the aluminum example appeared to be lacking the anti-oxidation compound on the connection.
As for determining if the corrosion is "excessive", not being an electrical engineer (I'm mechanical), I'd say a thermal scan is an effective way of spotting a connection that is not well made. As for the corrosion, if it is "growing" beyond the confines of the little compartment for each connection, then I would consider it unsafe, because the corrosion crud is likely conductive.
Eliminating the cause of the corrosion is important. It appears from some of the photos that there is more than just water there. Sometimes corrosive materials or moisture comes through conduits from some other place, especially if there is a difference in air pressure between adjoining rooms or to the outdoors. In that case electrical putty (we called it something less politically correct in the navy, beginning with "monkey-") in the conduits would help. I worked in a factory that had hydrochloric acid vapors in the air. We used a product called Z-Rust. It was a little plastic container of something that we stuck on the inside of enclosures with a peel off adhesive strip that came with it. They had to be changed periodically, but worked fairly well.
As someone else said, having a small amount of heat works well if the panel is in a place that could pick up dampness. We did that, too, and it helped.
Had been away for a few days. Just saw this.
Hmmm.
First one, with aluminum feed coming in the top, doesn't look like the corrosion was the primary problem. Looks to me like the lug on the left wasn't terminated correctly. Corroded aluminum conductor when it was terminated is a possibility. The lack of anti-oxidant or not properly applied is also a possible contributing cause. Aluminum conductors need to be cleaned, anti-oxidant applied and worked in. Then more compound applied before termination.
Sometimes one connection goes bad because the run was taken off a roll of cable that has sat around a bit. The exposed end can corrode under the insulation for a considerable distance. Care needs to be taken to either cut off this corroded end or clean it carefully. I like to use a stainless bristled wire brush, looks like a masochist's toothbrush, for removing corrosion and working in compound. It digs through corrosion and gets between the strands better than anything else I know. Of course the second connection, made with wire that came from the center of the coil tends to be less corroded.
I note the right hand connection seems have compound applied. Perhaps a bit less than I like to use, these compounds are cheap, but I note the set screw had compound applied. A good thing as it keeps the set screw from binding and corroding. If the screw binds you can be mislead into thinking the connection is tight when it is not.
Both sides look, going by the amount of set screw exposed, about equally tightened. A trick in visually checking connections is to note how how much of the set screw is exposed. A loose set screw will stick out more assuming similar lugs and wire sizes.
Contributing to the failure might be unbalanced loads. It doesn't matter much how good a connection is made if the connection is overloaded for a long time. A handy electrician's trick is to, on a single phase panel, to run the double-pole breakers down one side and group the 20 and 15 amp breakers down the other. This tends to automatically balance the loads.
A possibility is that the lug-to-bar connection is loose or corroded. And this caused the failure. Pretty rare this. One sign, given that the lugs, given the depth of the set screw, were tightened on the wire would be the lug twisting. To my eye it look like both lugs are dead straight. Could be the plastic held the lugs straight even though the screw, typically a torx head accessed by removing the setscrew from the lug, but usually they still twist a bit when loose. Something to look for when I tighten a connection.
Given that the right-hand connection has anti-oxidant I assume both did. Both, as I mentioned seem tightened equally. Unbalanced load could be an issue. I assume the lug-to-bar connection is tight enough. My bet is that the left-hand connection came off the coil first and was more corroded. It didn't get cleaned properly and compound worked in well enough. The resulting resistance caused the connection to heat up.
The compound baked off. Heat cycling likely loosened the connection making things worse. Heat melts the plastic in the panel and the insulation on the wire. Both of which give off HCl gas which, combined with humidity, contributes to the haze of rust in the panel. The chlorine, combined with heat and moisture, attacks both the aluminum and the tin plating on the aluminum lug. Which further damages the connection. A cascade reaction but one you caught fairly early.
Looks to me like the left-hand termination needs redoing. The lug needs replacing. If the bar is damaged, given the color and lack of shine I suspect it is, it needs replacing. Possibly the main depending on what the connections look like. When in doubt I replace them. I have sometimes found the main breaker and lug assembly at a supply house.
If not, given the cost and trouble of getting replacement parts, I would be tempted to replace the whole panel. If I could track down the same model number in a new panel I might save some time by just replacing the guts. That surface rust is no big problem. I might wire brush it and spray with some cold galvanizing if it is more extensive than it looks at first blush.
The second and third photos look to of the same panel, but different than the first photo, and have similar effects visible. I note that the staining is on the breaker and breaker connections but not visible in the panel to any great extent. Looks to me like water damage.
I suspect that similar staining can be seen on the inside of the panel cover where it fits closely to the breakers. I would suspect a missing or damaged weather head on a riser but the damage is localized to the front of the panel and it appears the panel is fed from the bottom, no riser. Also a bit unusual, but not unheard of, for a riser to go to a panel. Most go to a meter which is then fed by conduit, sometimes back to back, to the panel.
I think that the water was dirty, contaminated and likely rusty as the rust colored stains are not directly contiguous to the steel on the breakers. On second thought I note the the rust is in locations where iron are close by within the context of a closed panel. Clean, lightly chlorinated, water that set long enough in a live panel could cause such staining and corrosion before evaporating. The small currents moving across the water would make any dissolved iron and chlorine more corrosive.
The panel looks dry now. Possibly it was a one time thing. A broken washer hose or water line perhaps. Possibly moisture coming up from a underground conduit and condensing but I would think the corrosion would be more widespread and, because the back of the panel would likely be neared outside and so cooler, more concentrated on the back. Something I'm not seeing.
That sort of corrosion on the lugs on the breakers eliminated the chance they can be effectively tightened. The moisture also, possibly more importantly, can corrode the interiors of the breakers and displace the grease that keeps the pivots functioning smoothly. The breakers need replacing.
While your at it and the breakers are out I would use a strong light and mechanics mirror to inspect the buss bars and stabs for corrosion and damage. Doesn't look likely but if the buss bars or stabs are tinned aluminum they can turn to crud fairly quickly. Worse case, seeing as that it looks like a recent model, I would buy a copy of the panel and replace the guts.
Corrosion in panels is an issue but mostly it isn't a condensation issue as long as the panel is live and some power is used. Panels tend to be warm enough to drive off some moisture. Pays to make sure the weatherhead is on and in good condition. A drip loop in the service drop is required. Stuffing the base of the weatherhead, not the riser, or conduit on an under ground feed can help keep moisture out. Rarely, at least here in Florida, moisture can come in from the meter because of temperature differentials.
Worse corrosion issues I have seen were on panels located in pool pump rooms. The chlorine and moisture attack the aluminum. Best solution is to move the panels to outside the pump room. Once, when moving them was out of the question, we obtained gasketed fiberglass enclosures and mounted the panels inside them. To the we ran 2" PVC conduit routed through the wall to free air and protected by baffles from rain, two to each enclosure, one each top and bottom, on the lower one we mounted a 2" fan blowing in. This served to pressurize the enclosure keeping the chlorine and moisture out even if there were small leaks and it purged any fumes that got in when the panels were opened. We also used panels with copper buss bars. IMHO always a good idea.
The building owner like to have a heart attack when he got the bill but he paid. He saved money in the long run as he had gone through two panels in three years. The inspector was impressed. Interesting job.
Not sure if that answers your question.
Wow!Thanks! The tuition check is in the mail!Bob
View Image
Sojourners: Christians for Justice and Peace