# 300.5(F) "Cinders" What is it talking about?



## wildleg (Apr 12, 2009)

cinders tend to have potash in it, which makes it very acidic and caustic when any moisture is present.


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## macmikeman (Jan 23, 2007)

As a former "horticulturist" I can tell you that certain plants just love that stuff and grow quite well in cinder soil.........


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## wildleg (Apr 12, 2009)

as far as the article is concerned, though, cinders probably refers to broken up masonry, which is known to have sharp rough edges and damage waterproofing, cables, and other stuff if used for backfill.


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## frenchelectrican (Mar 15, 2007)

wildleg said:


> as far as the article is concerned, though, cinders probably refers to broken up masonry, which is known to have sharp rough edges and damage waterproofing, cables, and other stuff if used for backfill.


That is more common word for that as you described and unforetally pretty good precentage of contractors do not prepare the backfill correct at all.

but sometime I can heard word cinders from a byproduct from coal fired units their ash is pretty harsh.


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## Rodger (Jan 3, 2017)

wildleg said:


> as far as the article is concerned, though, cinders probably refers to broken up masonry, which is known to have sharp rough edges and damage waterproofing, cables, and other stuff if used for backfill.


That would make sense to me, but then why would the NEC use a word with a common dictionary definition and intend it to mean something that is not the standard definition, and not define their definition in their own list of definitions? !! Also....Does my sentence make any sense? :001_huh:


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## MikeFL (Apr 16, 2016)

A couple things come to mind:
1) Backfill over burried raceway, and,
2) Penetration through a wall.

Let's look at how the plumbers do it. If they're going to pass a copper pipe through a concrete wall, they're going to have a sleeve to prevent corrosion of the pipe. Copper in contact with concrete causes electrolysis. EMT will do the same in a moist and/ or salty environment, and if you're using EMT for a return path in that environment and crossing through a concrete wall, there's a valid argument that you should be sleeving it to isolate it from the concrete. I've seen this in coastal installations (public beach restrooms). It's cheaper than stainless.

You don't want backfill to injure your installation. Code requires you to protect from big rocks, sharp objects and materials which will cause corrosion or inability to compact the fill. I can see your local inspectors up there taking issue with burying your raceway in lava cinder and on that note suggest you ask them what their position is on it. Hasn't it been 30-40 years since the eruption? Surely there's some history demonstrating one way or the other what the effects are. In a best case scenario they're going to tell you you're fine ignoring it.


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## active1 (Dec 29, 2009)

It was a old school back fill material when coal cinder waste was much more common. When burning coal was very common waste product.
Homes had receptacles next to the trash to deposit the coal cinders.
Railroads probably had tons or cinders.
Used to see cinders along the tracks.
It was used for high school tracks.
Think of a waste product being used in place of gravel.

I have never seen it used in construction, but remains in the code book.
Unless the area has natural cinder it's something you don't need to worry about.


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## macmikeman (Jan 23, 2007)

It's more of that Manhattan talk that has dominated the code book from day one. You would think NYC was the only place with electrical wiring installed.


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## Rodger (Jan 3, 2017)

MikeFL said:


> EMT will do the same in a moist and/ or salty environment, and if you're using EMT for a return path in that environment and crossing through a concrete wall, there's a valid argument that you should be sleeving it to isolate it from the concrete.


I've seen EMT used underground .... make that, I've seem where EMT must have been used underground at some point in time. To be frank about it. The fact that it's allowed underground at all is baffling to me. I personally never use it underground. .. With or without an extra coat of paint.


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## splatz (May 23, 2015)

I figured it's referring to "cinders" as in coal ash. 

They make cinder block from cinders. It's cheap or free or maybe they even pay you to take it, where coal fired power plants have to get rid of mountains of the stuff. The DOT trucks spread it on icy roads for traction, or at least they used to. If you have a coal stove or coal furnace you pay the ash man to haul it off. 

I suspect it's just a free source of fill in some areas. It is real sharp scratchy stuff but I am not sure I could really see it scratching through a buried conduit but I could see it messing up a direct burial cable.


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## Southeast Power (Jan 18, 2009)

Rodger said:


> I've seen EMT used underground .... make that, I've seem where EMT must have been used underground at some point in time. To be frank about it. The fact that it's allowed underground at all is baffling to me. I personally never use it underground. .. With or without an extra coat of paint.


Some point in time, Broward County decided it was a good idea to run EMT in first floor slabs.
I'm still finding it.


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