Use of black pipe as conduit

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mrsandy

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Application is an RTD installed in a short thermowell, no head. A short piece of black pipe is used as a coupling to cover the exposed rigid sheath of the RTD sticking above the well. Liquidtight flex is then used to run the long RTD leads to a termination box approximately 30" away.

My customer insists that the black pipe fitting is not code legal but I cannot find any code against it.

Anyone have any history?

Thanks,

"Sandy"
 
I am guessing this would be a class 2 circuit. Its probably not required to be in a raceway at all. the black pipe is simply protection, not a raceway.
 
mrsandy said:
Application is an RTD installed in a short thermowell, no head. A short piece of black pipe is used as a coupling to cover the exposed rigid sheath of the RTD sticking above the well. Liquidtight flex is then used to run the long RTD leads to a termination box approximately 30" away.

My customer insists that the black pipe fitting is not code legal but I cannot find any code against it.

Anyone have any history?

Thanks,

"Sandy"
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Black pipe is not an NEC recognized raceway. I would be concerned with conductor damage since plumbing pipe does have a rough weld seam on the inside.
 
The RTD lead doesn't need to be in conduit in the first place, so anything you put it in is fine. You could wrap it with a lasagna noodle and they'd have to like it.
 
mdshunk said:
The RTD lead doesn't need to be in conduit in the first place, so anything you put it in is fine. You could wrap it with a lasagna noodle and they'd have to like it.
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A lasagna noodle? What about a spaghetti noodle?
 
ceb58 said:
RTD? What dose it stand for?
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Resistance Temperature something. Basically like a high-tech thermocouple is the way I always think of them. They're pretty accurate, and good for longer distances. They have three conductors, and they use the extra one to work out the resistance of the wire, so it can be discounted from the measurement.
 
mdshunk said:
Resistance Temperature something. Basically like a high-tech thermocouple is the way I always think of them. They're pretty accurate, and good for longer distances. They have three conductors, and they use the extra one to work out the resistance of the wire, so it can be discounted from the measurement.
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Then that would make it RTS:grin:
 
Resistance Temperature Device. The resistance of a the material changes with the change in temperature of the material. Three wire RTDs are pretty common but four wires are available for higher precision. Two wires are also available but lack the compensation that mdshunk described.
 
I appreciate all of the responses but does anyone know of chapter/verse I can use in defense of this installation.
 
It's one of those things where if it's not disallowed then it's allowed. Not really a code section simply how the code is written.

Like I tell other inspectors, just because you don't like it doesn't make it wrong.
 
mrsandy said:
I appreciate all of the responses but does anyone know of chapter/verse I can use in defense of this installation.
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I ain't no lectrishun, just a lowly ingeeneer, but I'd ask what chapter/verse is being used as an argument against that as a sleeve to protect it from the environment ... as has been said, from a code standpoint it does not appear anything is required. You need to be given the reason it is NOT ok to protect it.
 
LarryFine said:
I thought it was TDR - Temperature-Dependent Resistor.
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Whether you are half way making a joke, I cannot tell, but an RTD is a Temperature Dependent Resistor. Of course, darn near all conductors, semiconductors, and insulators have temperature dependent resistivity.

Now a TDR ... time domain reflectometer ... find bad spots in cables, measure lengths ...
 
mrsandy said:
I appreciate all of the responses but does anyone know of chapter/verse I can use in defense of this installation.
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Try art.353 I do not know if this is what you are referring to or not
 
mdshunk said:
Resistance Temperature something. Basically like a high-tech thermocouple is the way I always think of them. They're pretty accurate, and good for longer distances. They have three conductors, and they use the extra one to work out the resistance of the wire, so it can be discounted from the measurement.
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Resistance Temperature Detector.
The do work on a different principle than thermocouples.

Thermocouples are two dissimilar metals that produce voltage in proportion to the temperature. Used for high temperature applications. Requires very finicky installation, transmitters and special wires. Expensive.

RTD's are based on the resistance change of metals when they are at different temperatures.Low to moderate temperature applications, simple wiring and direct interface into many DCS's. Lower cost.
 
A thermistor is a temperature dependent resistor. It is a semi-conductive material that is coated with glass or ceramic; they are very accurate but have a very limited range and have a highly unlinear output unless compensation is used. A Resistance Temperature Device or Detector, known as an RTD, is made of metal and has a wider range. RTD's are far more common in an industrial environment then thermistors, at least the environments I have been in.
 
Your CUSTOMER does not like it and although it would be legal to install, it is the CUSTOMER that is questioning something that you are doing.

Why don't you just slip some PVC inside the 30" section of black pipe then make the transition to the liquid tight from the pvc and then you will make the customer happy.

Is that so hard?
 
mrsandy said:
............My customer insists that the black pipe fitting is not code legal but I cannot find any code against it.

.........."Sandy"
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Your customer may be thinking generally of language in the code found at 110.3(A)(1) and its' Fine Print Note which indicates the "suitability" of the product for a specific purpose. He's probably suggesting that the black coupling is not "listed" or "labeled" for this specific purpose and would have the installer use a fitting that is. :confused: :)
 
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