GFCI SLAVERY

Curt Fitz

New User
Location
Columbia Missouri
Occupation
Journeyman Wireman (IBEW)
How many receptacles can be “slaved” off a 20 amp GFCI receptacle? We are installing a series of sensors under sinks and would like to daisy chain as many as are allowed.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
There is no limit in the NEC. At one time certain manufacturers noted a limit on their instruction sheet but I have not seen a limit on any lately
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
Thats a circuit limit, not gfci limit. And doesnt apply to residential. The limit is the sum of the leakages of all the downstream devices being less than the trip limit. Or capacitive leakage if the run is long.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Isn’t there a 100ft total circuit length limit still? It was never in the NEC, but most GFCIs said it in their instructions. I don’t know if that’s still the case though.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Thats a circuit limit, not gfci limit. And doesnt apply to residential. The limit is the sum of the leakages of all the downstream devices being less than the trip limit. Or capacitive leakage if the run is long.
And even if the capacitive load is less than the trip value it will reduce the headroom for leakage in a load that itself meets the UL limit.

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suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
Don't know if its right or wrong, but many books say the receptacle limit on a circuit (in commercial at least) is whatever fits at 180VA per strap. A 20A circuit would support 2400VA which is 13 receptacles. A GFCI could be the first, last, nowhere, or anywhere in between. Residential circuits don't use this 180VA per strap rule so there is no limit to the number of receptacles on a circuit.
 
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