Wenatchee Home Inspections

I have written about grounding of receptacles before especially in reference to laundry circuits which begins with the 1947 NEC which required the laundry outlet in dwelling units to be a "3-pole type designed for grounding"





Here is the code section that first starts the beginning of grounded receptacles in residential (dwelling units).

1947 NEC
2124 Receptacle Outlets Required.

(b.) In Dwelling Occupancies.
In dwelling occupancies, in every kitchen, dining room, break/aet room, living room, parlor, library, den, sun room, recreation room, and bedroom, one receptacle outlet shall be provided lor every 20 linear ft. or major fraction thereof of the total (gross) distance around the room aa measured horizontally along the wall at the floor line. The receptacle outlets shall, insofar as practicable, be spaced equal distances apart. At least one receptacle outlet shall be installed for the connection of laundry appliances. This receptacle shall be 3-pole, of a type designed for grounding.

Receptacles in floor outlets shall not be counted as part of the required number of receptacle outlets unless located close to the wall.

So we can see here the sentence “At least one receptacle outlet shall be installed for the connection of laundry appliances. This receptacle shall be 3-pole, of a type designed for grounding.” has been added to the code section.  But the code was not specific on how the grounding conductor was to be installed here

In 1956 grounded receptacles was expanded  to include "open porches, breezeways, garages, and the like which may supply equipment to be used by persons standing on the ground".

1956 NEC
2124 Receptacle Outlets Required.

b. Dwelling Type Occupancies. In every kitchen, dining room, breakfast room, living room, parlor, library, den, sun room, recreation room and bedroom, one receptacle outlet shall be provided for every 12 linear feet or major fraction thereof of the total (gross) distance around the room as measured horizontally along the wall at the floor line. The receptacle outlets shall, insofar as practicable, be spaced equal distances apart. At least one receptacle of the

grounding type shall be installed for the connection of laundry appliances. Receptacles installed in or on open porches, breezeways, garages, and the like which may supply equipment to be used by persons standing on the ground shall be of the grounding type. Receptacle outlets in floor shall not be counted as part of the required number of receptacle outlets unless located close to the wall.

See Examples 1 and 4, Chapter 10.

Then 1962 brought about the requirement for branch circuits to "include or provide a grounding conductor to which the grounding contacts of the receptacle or cord connector shall be connected.

1962 NEC

210-7. Grounding Receptacles. Receptacles and cord connectors equipped with grounding contacts shall have those contacts effectively grounded. The branch circuit or branch circuit raceway shall include or provide a grounding conductor to which the grounding contacts of the receptacle or cord connector shall be connected. The metal armor of Type AC metal-clad cable, the sheath of aluminum sheathed cable, or a metallic raceway is acceptable as a grounding conductor. See Sections 210-21 (b). 250-45 and 250-59.

Exception: For extensions only in existing installations which do not have a grounding conductor in the branch circuit, the grounding conductor of a grounding type receptacle outlet may be grounded to a grounded cold water pipe near the equipment.

Additional Note: it was in the 1968 NEC 250.95 that required the equipment grounding conductor to be the same size as ungrounded conductor in 15/20/30 amp circuits. In the 1962 and 1965 NEC they allowed smaller EGC in approved cable systems , such as 16 gauge for up to 20 amps in approved cable assemblies.

Here are two other blogs on the history of grounding receptacles and installing a 3 prong receptacle on an ungrounded system-

Grounding receptacles the early years in Residential Home.

http://www.ncwhomeinspections.com/Grounding+receptacles+the+early+years+in+Residential+Homes

3 Prong Grounding Type Receptacles on 2 Wire Ungrounded System.  A little history

http://www.ncwhomeinspections.com/3+prong+grounding+type+receptacles+on+2+wire+ungrounded+system

"This alternating current thing is just a fad. It is much too dangerous for general use."

Thomas Edison

If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

WA Home Inspector Advisory Licensing Board

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