110V control and solenoid valve grounding

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kenaslan

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I have a situation that a 110V power circuit from a power panel fused down to 5A is run to a solenoid valve and some control circuits. They are all run in multiple TC cable in a 2" conduit. This is a class 1 Div 2 area. The control engineer wants to not run ground wires internal to the TC cable as he will have to add terminals to the JB, but instead use the conduit as the ground. I am under the impression that if you are using TC cable, the ground must be integral to the cable. Am I missing something? Is there an exception? Grounds are required in C1D2 areas regardless of voltage.
 
kenaslan said:
I have a situation that a 110V power circuit from a power panel fused down to 5A is run to a solenoid valve and some control circuits. They are all run in multiple TC cable in a 2" conduit. This is a class 1 Div 2 area. The control engineer wants to not run ground wires internal to the TC cable as he will have to add terminals to the JB, but instead use the conduit as the ground. I am under the impression that if you are using TC cable, the ground must be integral to the cable. Am I missing something? Is there an exception? Grounds are required in C1D2 areas regardless of voltage.
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Do you know where it states that the EGC must be an integral part of the TC.

I would think you just need to use proper bonding jumpers and connections on conduit and flexible conduit to insure continuity of the EGC (conduit)
 
Solenoids are nonsparking devices and need no special wiring in Cl 1 Div 2 areas. The EMT can be used as the grounding lead. Your other ‘control circuits’ may require something more, but we don’t know what that is, because you gave no information on them.
 
300.3(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1)through (B)(4).

As the Conduit is not the conductor "raceway" IMO, the individual TC cables are. The conduit is only for "protection" of the cables. To me it is silly to run 4 TC cables in a 2" GRC 100% of the way to a Scully Grounding system, but that is what the control engineer wants. Personally I think that once the voltage is over 60V the I&C engineers should have no say because they are not power and only have limited knowledge of Article 725, and they always want to argue with 250 as in their mind the grounding requirements of 250 are problematic to their equipment. They do not want grounds in any cable anytime, ever. A 110V branch circuit requires a EGC. Just because it terminates in a PLC after going through a NO/NC contact and is classified as a Remote control and signaling circuit as defined be 725.41(B) still needs a EGC back to the power panel.
Dsg319 said:
Do you know where it states that the EGC must be an integral part of the TC.

I would think you just need to use proper bonding jumpers and connections on conduit and flexible conduit to insure continuity of the EGC (conduit)
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Section 300.3(B) is a good example of one Code Making Panel (CMP), “stepping on the toes” of another one and the Technical Correlating Committee (TCC) not correcting it. In this case, CMP3 is making a statement that should belong to CMP5. Taking the rule literally, a “…raceway, auxiliary gutter, cable tray…”, etc. could never act as an equipment grounding conductor (EGC) since it would need to be contained within itself. CMP5 uses the much simpler concept of saying the EGC needs to be “run with or enclosing” the circuit conductors. [Section 250.118] This has been pointed out many times to both CMPs and the TCC. The mental and verbal gymnastics to avoid correcting this obvious error have been incredible.

That said, a recognized Section 501.10(B) raceway (EMT is not one) is an acceptable EGC if otherwise installed correctly. NOTE: Grounding and bonding requirements are virtually identical in Divisions 1 and 2. [Section 501.30] There are a few minor Exceptions in Division 2 but they don’t apply in the OP description. Also see Section 250.100.

Be careful that you have a properly installed motor disconnect “in sight” of your MOV.
 
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I will say it gets frustrating with the code contradicting itself.

As this is a large industrial location (refinery) the "insight" rule does not apply as there is a written LOTO policy.

Back on topic, I did find this from the IAEI;
To determine whether raceways and other metal enclosures for signaling use are required to be grounded, we must first determine whether the system is required to be grounded, that is, whether the voltage system is required to include a grounded conductor. This can be determined from 250.20 in most cases (see 250.162 for dc systems). On one hand, according to 250.20(A), most Class 2 systems used for such purposes as doorbells, garage door openers, and thermostats are not required to be grounded because they are less than 50 volts, are derived from grounded 120-volt systems, and are not installed as overhead conductors outside of buildings. On the other hand, a 120-volt, Class 1 circuit would usually have to be grounded in accordance with 250.20(B)(1). Second, according to 250.112(I), the equipment supplied by these circuits is only required to be grounded where system grounding is required by Part II (250.20) or Part VII (250.162). Thus the equipment supplied by or containing the Class 2 circuits in this example is not required to be grounded but the equipment associated with the Class 1 circuits mentioned is required to be grounded. These requirements are reiterated by 250.86, which refers specifically to 250.112(I). The raceway shown in photo 9 is not required to be grounded because it contains only 24-volt Class 2 circuits that are derived from a 120-volt system.


A circuit or equipment that is not required to be grounded by the rules discussed so far in Article 250 may be required to be grounded or bonded in other cases and by other rules. These requirements may be found in Article 725 or in other articles. For example, Section 725.57 imposes additional requirements on Class 2 and Class 3 circuits that extend beyond one building and are subject to accidental contact with higher voltages. In such cases, the Class 2 or Class 3 circuits are required to be treated as communications conductors in certain ways which may include connections to grounded primary protectors and grounding of metallic cable sheaths or shields. In addition, non-current-carrying metal parts of all electrical systems must be bonded in hazardous (classified) locations. Raceways or enclosures may not always be required for signaling circuits in such areas if the circuits are also nonincendive or intrinsically safe, but where metal raceways or enclosures are used in hazardous areas, they must be bonded to comply with Section 250.100.


This article has briefly examined why and how signaling circuits are given special or different treatment in the NEC. The classifications of the circuits covered by Article 725 are determined and differentiated by use and power limitations. Class 2 and Class 3 circuits are most commonly defined by listed power supplies. The inherent power limitations of these supplies justifies the use of alternative wiring methods and different schemes for protecting equipment and persons from the possible hazards of these systems. In fact, in many cases the hazards are already significantly reduced by the nature and sources of the circuits themselves. Article 725 provides somewhat relaxed requirements for installations of signaling circuits. However, in order to maintain the power limitations upon which the relaxed rules are based, requirements for separations from higher-powered circuits and systems must be significantly more restrictive, and these restrictions must be carefully observed.
 
My answer is disregarding the classified location aspect, because it doesn't apply to my answer and starts out with a question- why run a cable inside a raceway? If you have a raceway why not just run art 310 conductors within it, then you only need 1 EGC run within as well.

If this is not a "raceway" but rather just a sleeve - then you have a cable wiring method and have same issue with multiple EGC's even if you did not have the sleeve.
 
The SOP in refineries and the petrol-chemical industry is to run all cables TC-ER, MC-HL etc. in tray, and into and out the tray are sleeved in GRC. This is the standard procedure in the RCS (Refining Core Specifications) If no tray is used, cable is still run, but 100% enclosed in GRC. I think this is because they never consider that conduit is an effective EGC. the smallest spark in an oil refinery could be a disaster. The larger issue is the constant struggle with instrumentation engineers that don't want grounds of any sort. They believe that 110V, if used for a MOV or dry contact (signaling) when coming from a power panel does not need a ground because it is now a "control" circuit.
 
The opening statement of Section 250.100 that I refereed to is:
250.100 Bonding in Hazardous (Classified) Locations.
Regardless of the voltage of the electrical system, the electrical continuity of non–current-carrying metal parts of equipment, raceways, and other enclosures in any hazardous (classified) location, as defined in 500.5, 505.5, and 506.5, shall be ensured by any of the bonding methods specified in 250.92(B)(2) through (B)(4).

What is often overlooked is this applies even to intrinsically safe or non-incentive systems. This is because circulating ground currents are still capable of igniting hazardous atmospheres.

Also See Section 501.30. [EDIT ADD: Pay particular attention to:
501.30(A) Bonding.
The locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes, but bonding jumpers with proper fittings or other approved means of bonding shall be used. Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, and so forth between Class I locations and the point of grounding for service equipment or point of grounding of a separately derived system.]

FWIW Just a side-note: I have worked in refineries and other classified locations all over the world for over 50 years.
 
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rbalex said:
The opening statement of Section 250.100 that I refereed to is:
250.100 Bonding in Hazardous (Classified) Locations.
Regardless of the voltage of the electrical system, the electrical continuity of non–current-carrying metal parts of equipment, raceways, and other enclosures in any hazardous (classified) location, as defined in 500.5, 505.5, and 506.5, shall be ensured by any of the bonding methods specified in 250.92(B)(2) through (B)(4).

What is often overlooked is this applies even to intrinsically safe or non-incentive systems. This is because circulating ground currents are still capable of igniting hazardous atmospheres.

Also See Section 501.30. [EDIT ADD: Pay particular attention to:
501.30(A) Bonding.
The locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes, but bonding jumpers with proper fittings or other approved means of bonding shall be used. Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, and so forth between Class I locations and the point of grounding for service equipment or point of grounding of a separately derived system.]

FWIW Just a side-note: I have worked in refineries and other classified locations all over the world for over 50 years.
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Thank you, I am aware of the Bonding requirements. Like you I have been in the industry for over 40 years. My OP was for EGC requirements for 110V control circuits. However regardless of what the code states, I finally found SP-60-38 that clearly states that no conduit shall be used as a return ground path. That the EGC MUST be run in the cable assembly. The I&C engineer is not happy, but it is the client requirements.

My biggest beef and it is off topic, is that I&C people always want to override the power people. They just dont have the same understanding of someone that has studied the NEC to the extent that power people have. I might not have a PE but as a retired EC and union electrician, I do know code.
 
I gave you the best NEC references I could. Very few engineers/designers would consider that a client’s spec would override the Code, but I suppose it would depend on the AHJ. I do know FedOSHA would frown at such a move. As a PE, I’d refuse to seal such a design.
 
let me rephrase, as I did not phrase it correctly, not override, make more restrictive, as the code is the minimum. so if the code says you can use the conduit as a return ground, but the client says that is not good enough they will not allow it they demand a stricter requirement. And I agree with all your code references.
 
A more restrictive requirement is fine if you don’t mind a higher cost that doesn’t actually improve performance or safety.

Non–current-carrying metal parts of equipment, raceways, and other enclosures still need proper bonding (basically all the way back to the source) whether they are used as EGCs or not AND the voltage level is irrelevant, control system/instrumentation or not.
 
rbalex said:
A more restrictive requirement is fine if you don’t mind a higher cost that doesn’t actually improve performance or safety.

Non–current-carrying metal parts of equipment, raceways, and other enclosures still need proper bonding (basically all the way back to the source) whether they are used as EGCs or not AND the voltage level is irrelevant, control system/instrumentation or not.
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That sort of was my thinking. This no different than whether to pull an EGC or not in general classification areas. There are some that say metal raceway not reliable enough and there are others that say it is just as good or even better than a wire type EGC. NEC says either is fine for most general uses.
 
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