Subpanels

J

Jimmy7

Senior Member
Location
Boston, MA
Occupation
Electrician
How long have they been separating the grounds and neutrals in a subpanel? When did it come into the code?
 
infinity said:
Unless they're in separate structures a 100 years ago?
Click to expand...
Little Bill said:
In the same building, forever, in a detached building, since around the 2008 code.
Click to expand...
I believe that before 2008 you were allowed to run a separate ground if you wanted to. I vaguely remember doing a job and being turned down for running an equipment grounding conductor to a separate structure. I appealed, he checked, and all was good.
 
It’s funny, I see it all the time with panels in the same structure, where they have a second N-G bond. I always wonder who these guys were that thought this was proper.
 
1986. That's when sec. 250 really changed everything. I just finished a grocery store build that had main panels from the 1980s and had all neutrals and grounds bonded throughout sub panels.
 
herding_cats said:
1986. That's when sec. 250 really changed everything. I just finished a grocery store build that had main panels from the 1980s and had all neutrals and grounds bonded throughout sub panels.
Click to expand...
It was decades before that. This is from earliest digital version that I have and this if from the 1965 NEC.


250-61. Grounding Equipment to Circuit Conductor.
The grounded service conductor on the supply side of the service disconnecting means may be used for grounding meter housing and service equipment and metallic enclosures and guards. The grounded circuit conductor on the load side of the service disconnecting means shall not be used for grounding equipment, cable armor, or metal raceways except as provided in Section 250-57 (b-4), and in Section 250-60.
Click to expand...
I also dug this up from the 1937 NEC:

2562. Grounding equipment to Circuit Conductor Prohibited. The grounded circuit conductor of an interior wiring system shall not be used for grounding equipment, cable armor, or metal raceway, except by special permission in sub-paragraph 2559-c.
Click to expand...
 
Last edited:
As I recall and I was first licensed in 81" you could only use the grounded conductor "neutral" for stoves driers and the meter socket and in the main service disconnect for grounding.. Always been that way afaik
 
Interesting. Maybe the '84 NEC removed the EMT as qualified ground? I was 13 then so I'm not sure. But I was wiring homes with my Dad.
 
Yes. There are buildings that do service work on, all EMT with no green wire. There's 1000's of feet of EMT that I installed with no green wire. It hasn't been until about the first decade of the 21st century that the Cult Of The Green Wire's cold, icy, money wasting fingers got such a firm grip on the electrical world.
 
herding_cats said:
So a 1/2" run of EMT servicing a 1 hp motor (120vac, 20A circuit, #12 THHN) with no ground wire still is legal? That's what I'm saying.
Click to expand...
Yes. All sizes of EMT are a listed EGC. The 1/2" EMT will likely have a lower impedance than the #12 EGC.

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
(1) A copper, aluminum, or copper-clad aluminum conductor. This conductor shall be solid or stranded; insulated, covered, or bare; and in the form of a wire or a busbar of any shape.
(2) Rigid metal conduit.
(3) Intermediate metal conduit.
(4)Electrical metallic tubing.
(5)Listed flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. The size of the conduit does not exceed metric designator 35 (trade size 11∕ 4).
d. The combined length of flexible metal conduit, flexible metallic tubing, and liquidtight flexible metal conduit in the same effective ground-fault current path does not exceed 1.8 m (6 ft).
e.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, a wire-type equipment grounding conductor shall be installed.
(6)Listed liquidtight flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings.
b. For metric designators 12 through 16 (trade sizes 3∕ 8 through 1∕ 2), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. For metric designators 21 through 35 (trade sizes 3∕ 4 through 11∕ 4), the circuit conductors contained in the conduit are protected by overcurrent devices rated not more than 60 amperes and there is no flexible
metal conduit, flexible metallic tubing, or liquidtight flexible metal conduit in metric designators 12 through 16 (trade sizes 3∕ 8 through 1∕ 2) in the effective ground-fault current path.
d. The combined length of flexible metal conduit, flexible metallic tubing, and liquidtight flexible metal conduit in the same effective ground-fault current path does not exceed 1.8 m (6 ft).
e. 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, a wire-type equipment grounding conductor shall be installed.
(7)Flexible metallic tubing where the tubing is terminated in listed fittings and meeting the following conditions:
a. The circuit conductors contained in the tubing are protected by overcurrent devices rated at 20 amperes or less.
b. The combined length of flexible metal conduit, flexible metallic tubing, and liquidtight flexible metal conduit in the same effective ground-fault current path does not exceed 1.8 m (6 ft).
(8)Armor of Type AC cable as provided in 320.108.
(9)The copper sheath of mineral-insulated, metal-sheathed cable Type MI.
(10)Type MC cable that provides an effective ground-fault current path in accordance with one or more of the following:
a. It contains an insulated or uninsulated equipment grounding conductor in compliance with 250.118(1).
b. The combined metallic sheath and uninsulated equipment grounding/bonding conductor of interlocked metal tape–type MC cable that is listed and identified as an equipment grounding conductor
c. The metallic sheath or the combined metallic sheath and equipment grounding conductors of the smooth or corrugated tube-type MC cable that is listed and identified as an equipment grounding conductor
(11)Cable trays as permitted in 392.10 and 392.60.
(12)Cablebus framework as permitted in 370.60(1).
(13)Other listed electrically continuous metal raceways and listed auxiliary gutters.
(14)Surface metal raceways listed for grounding.
Informational Note: For a definition of effective ground-fault current path, see Article 100.
Click to expand...
 
Given the painted surfaces of motor enclosures, how EMT can separate, or how fittings can be loose, I have to run direct green wire from the source and attach directly to the equipment ground.
 
One of my guys got called out on inspection using bare copper wire as GEC (he stripped a 20' section of ROMEX and pulled that into EMT). Inspection said no bare copper GEC allowed. I think he was trying to bust him for using ROMEX that had been stripped. It was a 30A 240v run to an electric water heater.
 
herding_cats said:
One of my guys got called out on inspection using bare copper wire as GEC (he stripped a 20' section of ROMEX and pulled that into EMT). Inspection said no bare copper GEC allowed. I think he was trying to bust him for using ROMEX that had been stripped. It was a 30A 240v run to an electric water heater.
Click to expand...
There is no rule that says EGC has to be insulated. There is a rule that says you can't use 12AWG EGC on a 30A circuit.
 
You must log in or register to reply here.
Top