We just bought a Chicago-area house and found that there's no ground wire in some of the recently re-wired areas. I thought that the national electrical code requires a ground wire for new construction and remodels, as opposed to relying on the steel conduit as ground. Is this correct?
asked Sep 22, 2015 at 15:24
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I'm not sure exactly what you're asking. If installed properly, metallic conduit and tubing can still be used as an equipment grounding conductor (EGC) (as of NEC 2014). As for when equipment grounding conductors started to be required, I'm not sure. If you know when the remodel happened, somebody might be able to tell you if it was required at that time.– Tester101Commented Sep 22, 2015 at 20:13
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But then all outdoor EMT would be required to have it I would think? Maybe it's due to vibration from the AC, or a combination of vibration and corrosion leading to degradation of the EGC continuity over time. EMT would present a smooth surface rubbing inside its connector when vibrated, whereas IMC or RMC are usually self-threaded and cannot easily loosen by vibration (I notice there's no mention of compression connectors used on the rigid types, but those connectors are heavier than the EMT version so maybe that takes care of it?)– MikeCommented Jan 16, 2020 at 8:48
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2 Answers
Conduit (RMC, IMC or EMT) is an NEC-accepted ground path. So, if the wires are in steel conduit, no OTHER ground wire is required.
If that gives you concerns, you might find this link reporting research into the effectiveness of conduit as a ground relieves them.
Updated link to NEMA Technical Services Department Bulletin 97.
answered Sep 22, 2015 at 20:18
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@Tester101 I do not see an "exclusion for residential use" in the code. That would surely be there if the NFPA agreed with your contention. While conduit in houses may not be overly common outside of Chicago, it's still a code-compliant grounding conductor if it is used.– EcnerwalCommented Sep 22, 2015 at 21:12
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1I called my local inspector; it ends up that grounding wire is not required, and using steel conduit to carry ground is perfectly acceptable. I'll edit the question. Commented Sep 23, 2015 at 0:43
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One observation is that the link shows images of conduit inside a clean, dry, maintained industrial facility. May not be applicable to exterior conduit. Commented Oct 2, 2021 at 17:50
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Due to corrosion issues. Looking at another post, 358.60 (B) requires an additional ground conductor for exterior air conditioning and refrigeration equipment when using EMT. Commented Oct 2, 2021 at 20:39
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Nobody hard pipes a condenser. You buy the whip with four wires in it. And a cheater box disconnect with an outlet in it.– MazuraCommented Oct 15, 2022 at 17:19
National Electrical Code does allow metallic conduit and tubing to be used as an equipment grounding conductor, as long as it's installed properly.
However, before using it as such in an existing installation, you should verify that it provides an adequate continuous path to ground.
National Electrical Code 2014
Chapter 3 Wiring Methods
Article 342 Intermediate Metal Conduit: Type IMC
342.60 Grounding. IMC shall be permitted as an equipment grounding conductor.
Article 344 Rigid Metal Conduit: Type RMC
344.60 Grounding. RMC shall be permitted as an equipment grounding conductor.
Article 348 Flexible Metal Conduit: Type FMC
348.60 Grounding and Bonding. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
Where flexibility is not required after installation, FMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(5).
Where required or installed, equipment grounding conductors shall be installed in accordance with 250.134(B).
Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102.
Article 350 Liquidtight Flexible Metal Conduit: Type LFMC
350.60 Grounding. Grounding and bonding for LFMC shall be installed in accordance with 350.60(A) and (B).
(A) If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
Where flexibility is not required after installation, LFMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(6).
Where required or installed, equipment grounding conductors shall be installed in accordance with 250.134(B).
Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102.
(B) Where Air Conditioning or Refrigerating Equipment is installed outdoors, an equipment grounding conductor per 250.118(1) shall be provided within the raceway and shall be sized per 250.122.
Article 358 Electrical Metallic Tubing: Type EMT
358.60 Grounding. Grounding and bonding EMT shall be installed in accordance with 358.60(A) and (B).
(A) EMT shall be permitted as an equipment grounding conductor
(B) Where Air Conditioning or Refrigerating Equipment is installed outdoors, an equipment grounding conductor per 250.118(1) shall be provided within the raceway and shall be sized per 250.122.
Article 360 Flexible Metallic Tubing: Type FMT
360.60 Grounding. FMT shall be permitted as an equipment grounding conductor where installed in accordance with 250.118(7).
answered Sep 23, 2015 at 19:40
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1Guessing that the 358.60(B) grounding conductor is required due to expected corrosion. Commented Nov 14, 2017 at 2:25
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1358.60(B) no longer exists as of the 2017 NEC; the only requirements for EGCs in EMT as of 2017 are the long-standing double-ground-path requirements in health-care facilities and the ground-wire requirement for HVAC equipment on rooftops found in 440.9. (The latter is needed because conduit using compression or setscrew fittings will come apart at the fittings if stepped on repeatedly, thus rendering it unusable as a grounding path.) Commented Jan 17, 2020 at 0:11