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Condensation in Subpanel

Posted by bltglt (My Page) on
Tue, Aug 10, 10 at 12:58

I have a very unusual issue occurring in my subpanel right now. I installed this subpanel about 2 years ago and recently noticed that one of the two metal anchors I used is rusting over. This subpanel is mounted to a basement wall and is about 1 1/2 feet above ground level. It is actually at the same level as the main box that was installed in early 2008. These two anchors look like they're made of brass or something similar. They're not aluminum or silver in appearance. I don't have any water marks anywhere or any drips. All the wiring, breakers, and bus bars look clean and dry. What's unusual is the fact that one of these anchors has rusted over but the other one still looks almost brand new with just a very very slight amount of oxidation. They are spaced about 6 inches apart. Why would one corrode and the other not corrode? Is it something to be concerned about? Also, my basement is usually somewhat damp. I never have more than a 1/2 of water in the basement. We use a de-humidifier, but I've noticed that several of my tools I keep down there have developed some rust on them over the last two years.


Follow-Up Postings:

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RE: Condensation in Subpanel

Here is a link with a picture that shows the type of anchor I used. The one I used is the sixth one from the left (the middle one). http://www.google.com/imgres?imgurl=http://www.tradenote.net/images/users/000/398/749/products_images/545019.jpg&imgrefurl=http://www.tradenote.net/anchors_3/&usg=__FQgc6Bq--14WViDfEz7UMuZA06A=&h=432&w=764&sz=35&hl=en&start=18&sig2=wajgkJWl5NaGJmoPPiyPrw&tbnid=j5nA4Pjcz_p5XM:&tbnh=143&tbnw=201&ei=6YZhTLCOJ4G78gbOnbSDCg&prev=/images%3Fq%3DBrass%2Bwall%2Banchor%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1280%26bih%3D614%26tbs%3Disch:10682&um=1&itbs=1&iact=hc&vpx=859&vpy=251&dur=374&hovh=169&hovw=299&tx=136&ty=142&oei=1oZhTPSHMoP98AatxoGICQ&esq=2&page=2&ndsp=18&ved=1t:429,r:16,s:18&biw=1280&bih=614


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RE: Condensation in Subpanel

Very few steel anchors (like some grades of stainless steel) withstand concrete exposure long term.

Portland cement is alkaline and very corrosive.

Unless the anchor is loose there is nothing to worry about.

There can be advantages to threaded type anchors that can be tightened again.

If it is actually loose, try setting it again.
If it is tight, leave it alone.


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RE: Condensation in Subpanel

O.k., I'll just leave it alone. They are certainly not loose, just one has rust forming on it. I did some more research and found out that they are made of steel with a zinc coating. They are called Hit Anchors. The electricians who installed the main breaker box used plastic anchors and screws. None of them are rusting, but I felt like plastic anchors would not be strong enough. Also, I forgot to mention that the wall is not poured concrete; it is a brick wall basement with mortar in between. I guess if the anchors ever fail (I don't want to use plastic because I don't trust it) I could just mount the subpanel to a big sheet of plywood. Here is a good link that gives detailed information about these anchors: http://unistar.en.alibaba.com/product/254403666-209466690/Hit_Anchor.html?tracelog=cgsotherproduct1 I don't know if these are the same brand or not, but they look 100% identical to the ones I used.


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RE: Condensation in Subpanel

" I guess if the anchors ever fail (I don't want to use plastic because I don't trust it) I could just mount the subpanel to a big sheet of plywood."

Plastic screw anchors in masonry for shear loads are just fine.

If the there is not a wood panel around the box, how are you fastening cables with the required distance?

That is why residential panels are often mounted on pieces of 2x lumber.
It is easy to use cable staples to secure the wiring.


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RE: Condensation in Subpanel

I just staple the cables down on the wood support boards that rest on the brick wall. Maybe it's not in compliance with the code, but it's what the electricians did with the main panel. I just tried to copy them the best that I could. What really concerns me is the fact that the rust on the anchor is right over the incoming neutral connection. I really don't understand why they would rust because they're designed for us in masonry, bricks, and blocks. My basement does have moisture because almost every single nail down there has rust on it. About a year and a half ago, I installed some new plastic switch boxes for new lighting. Every box's mounting nails are now rusted over completely. Anything metal left out exposed will rust. With the anchor, at one point I remember putting some enamel point over the rusting anchor, but the rust is still there. The anchors are rock solid. After I hammered in the nail that expands it, the anchors have never budged. If I ever decided to not use the anchors and wanted to get rid of them, I would have to grind them down to be even with the wall. There is no other way of removing them. What concerns me is possibly the rust making a path to the neutral creating a connection between ground and neutral. I'd rather not make any changes unless necessary, but I want some opinions from the pros.


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RE: Condensation in Subpanel

"I just staple the cables down on the wood support boards that rest on the brick wall. Maybe it's not in compliance with the code, but it's what the electricians did with the main panel. I just tried to copy them the best that I could."

Sounds like it is unlikely to be close enough to the exit from the panel in every case.

" I really don't understand why they would rust because they're designed for us in masonry, bricks, and blocks."

Outside of gold there are not a lot of metals that stand up to mortar, Portland cement, or concrete.

Surface rust does not mean anything.


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RE: Condensation in Subpanel

brickeyee, I have another question for you about something that happened a couple of years ago with this subpanel (which has unfortunately been nothing but a big headache). When I first installed this subpanel, I used 6 awg wire and a 50 amp breaker. I wasn't certain how much of a load I would be putting on the panel so I made sure it was rated for a heavy load. The panel is a Square D homeline subpanel. Here's a link that shows what it looks like: http://www.google.com/imgres?imgurl=http://www.diychatroom.com/attachments/f18/15219d1259954920t-problems-square-d-subpanel-100_3664.jpg&imgrefurl=http://www.diychatroom.com/f18/problems-square-d-subpanel-58405/&usg=__MUKaB26mjqQSTp35wCUzvSzzsB4=&h=450&w=600&sz=113&hl=en&start=0&sig2=OcR-S0L5piw_4zr0IgWsaw&zoom=1&tbnid=-_oMAkIHAj22wM:&tbnh=135&tbnw=191&ei=1AFwTLHhEMP68AaY7MXpCg&prev=/images%3Fq%3DSquare%2BD%2Bsubpanel%26um%3D1%26hl%3Den%26biw%3D1280%26bih%3D614%26tbs%3Disch:104&um=1&itbs=1&iact=hc&vpx=754&vpy=112&dur=23&hovh=194&hovw=259&tx=118&ty=107&oei=1AFwTLHhEMP68AaY7MXpCg&esq=1&page=1&ndsp=22&ved=1t:429,r:4,s:0&biw=1280&bih=614 . This is a picture of the exact panel, I posted this question on another forum and didn't really get a good answer. In the picture, the subpanel is fed by 10 awg wire 30 AMP service instead of the original 50 AMP 6 awg wire. What happened was the left screw on the top hot bus bar broke loose after I installed the 6 awg wire. It did not initially break. It broke about 3 months after installation. When it was installed, I had someone who has an electrical engineering degree (works for a big company setting up their electrical systems) inspect my work, and he thought that everything was fine. I initially screwed the screw back in and used JB weld to hold it in place. I eventually replaced the guts of the panel with those from another subpanel (what's shown in the picture). I paid twice for this. Someone on another forum commented that this shouldn't have happened; a 6 awg wire shouldn't have broke that screw loose. This panel was also built for tandem breakers. I originally had two tandem breakers and the plastic guide hook at the base of the tandem breaker just broke off for no apparent reason about 6 months after installation. I found out about it when I saw a little piece of plastic laying at the bottom of the subpanel. Since the photo I posted, I cleaned the wiring up a little bit in the panel and it looks neater now. Did I overtighten the 6 awg wire or was this a manufacturer's defect? If 6 awg wire can do this, I wonder what 2 awg wire would do to this subpanel!


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RE: Condensation in Subpanel

Blglt, please start a new thread on this. This time either use tinyurl.com to shrink your links, or put your link in the "Optional link URL" field at the bottom of the message.

The problem is, I can't easily read your message because the ridiculously long ULR makes it about 5 times as wide as my computer's screen. I'm sure I'm not the only one. Sideways scrolling is pretty tedious and annoying.

Thanks.


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