RMC Compression Fitting

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al hildenbrand

al hildenbrand

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Minnesota
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Electrical Contractor, Electrical Consultant, Electrical Engineer
Is a rigid metal conduit compression coupling suitable for direct burial?

Situation: 3/4" RMC cut ends (no thread) meet in a trench and are coupled together with a common (read inexpensive) RMC compression coupling. Does filling the trench with soil go beyond the allowed use of the coupling?

Reading from the White Book yields no direct statement about marking or use, in sections DWTT and DYIX, at least that I am understanding.
 
LJSMITH1 said:
Unless its listed raintight AND you provide additional corrosion protection, I don't see a problem with it.
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Really?

A 'normal' threaded RMC coupling is not listed as rain tight and they are not.

The are also do not generally requires additional protection.
 
mdshunk said:
iwire said:
The are also do not generally requires additional protection.
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Typing on your phone?
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What's the matter, you don't speak Yoda?
the_real_yoda.gif
 
I kind of like not to use them unless there is a specific reason for using them I am torn a little between quality of work issues and it is perfectly legal contractor makes more money issues. They are most commonly used by me when a concrete encased pipe is hit in the deck and needs repair. Other than that I dont like to use them.
 
al hildenbrand said:
Is a rigid metal conduit compression coupling suitable for direct burial?

Situation: 3/4" RMC cut ends (no thread) meet in a trench and are coupled together with a common (read inexpensive) RMC compression coupling. Does filling the trench with soil go beyond the allowed use of the coupling?

Reading from the White Book yields no direct statement about marking or use, in sections DWTT and DYIX, at least that I am understanding.
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Seem to work fine for me the last 25 years. Did they change something other than it raining underground?
 
jrannis said:
Seem to work fine for me the last 25 years. Did they change something other than it raining underground?
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I don't think anything's changed, that I'm aware of. . . .I'm just looking for something I can point at that says there is, or is not, a permission to use a simple RMC compression coupling in direct burial installations. The text in the White Book is vague.

Is the absense of a White Book limitation on the coupling a permission?
 
al hildenbrand said:
I don't think anything's changed, that I'm aware of. . . .I'm just looking for something I can point at that says there is, or is not, a permission to use a simple RMC compression coupling in direct burial installations. The text in the White Book is vague.

Is the absense of a White Book limitation on the coupling a permission?
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I really never gave it a second thought. Some brands dont work very well on IMC.
 
al hildenbrand said:
I don't think anything's changed, that I'm aware of. . . .I'm just looking for something I can point at that says there is, or is not, a permission to use a simple RMC compression coupling in direct burial installations. The text in the White Book is vague.

Is the absense of a White Book limitation on the coupling a permission?
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I don't believe it has to be listed specifically for direct burial...

NEC 2008

334.10 Uses Permitted.

(B) Corrosive Environments.

(1) Galvanized Steel, Stainless Steel, and Red Brass RMC. Elbows, couplings, and Fittings. Galvanized steel, stainless steel, and red brass RMC elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.​
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​
 
Smart $ said:
I don't believe it has to be listed specifically for direct burial...
NEC 2008

344.10 Uses Permitted.

(B) Corrosive Environments.

(1) Galvanized Steel, Stainless Steel, and Red Brass RMC Elbows, Couplings, and Fittings. Galvanized steel, stainless steel, and red brass RMC elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.


​
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Ahh, thanks. That got me back to earth. I was overthinking by going to the White Book first.

The Fine Print Note at the bottom of 344.10 leads to 300.6.

Specifically 300.6(A),
300.6(A)(3),
and 300.6 FPN just after (D).
2008 NEC
300.6 Protection Against Corrosion and Deterioration.

FPN: In general, areas where acids and alkali chemicals are handled and stored may present such corrosive conditions, particularly when wet or damp. Severe corrosive conditions may also be present in portions of meatpacking plants, tanneries, glue houses, and some stables; in installations immediately adjacent to a seashore and swimming pool areas; in areas where chemical deicers are used; and in storage cellars or rooms for hides, casings, fertilizer, salt, and bulk chemicals.
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The NEC Handbook goes on to add, in commentary after 300.6(A)(3) that:
2008 NECH Commentary
After 300.6(A)(3)

Galvanized rigid steel conduit and steel intermediate metal conduit do not generally require supplementary corrosion protection.
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As I read 344.10(B)(1), the comma and "or" between "in direct contact with the earth" and the phrase "in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition." isolates the object of "where protected by corrosion protection and judged suitable for the condition." to only "areas subject to severe corrosive influences."
 
al hildenbrand said:
As I read 344.10(B)(1), the comma and "or" between "in direct contact with the earth" and the phrase "in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition." isolates the object of "where protected by corrosion protection and judged suitable for the condition." to only "areas subject to severe corrosive influences."
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You are correct. I had realized such after posting, but it was past the edit time limitation had expired. It was also way toooo late into MY night... glad you caught it and corrected me ;)
 
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