GFCI Thingy on Hair Dryers

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Why do hair dryers have a GFCI plug considering the dryer itself is double insulated?

..................
 

Attachments

  • 1616044710891.png
    1616044710891.png
    394.4 KB · Views: 4

ppsh

Member
Location
CA
Occupation
Electrician
From a UL document.
IDCI (Immersion Detection Circuit Interrupter) — A component device that interrupts the supply circuit to an immersed appliance. When a conductive liquid enters the appliance and contacts both a live part and an internal sensor, the device trips when current flow between the live part and the sensor exceeds the trip current value. The trip current may be any value below 6 mA sufficient to detect immersion of the connected appliance. The function of an IDCI is not dependent on the presence of a grounded object. Listed products that contain IDCIs or ALCIs have been investigated for installation in applications in accordance with Section 422.41 of the NEC.
 

480sparky

Senior Member
Location
Iowegia
Being double-insulated has nothing to do with it.

They're installed because not every bathroom has GFCI receptacles. And not all GFCI's that are installed actually work as intended.
 

drcampbell

Senior Member
Location
The Motor City, Michigan USA
Occupation
Engineer
They might be insulated against incidental contact, but they're not insulated against submersion.

And while there might be one or two celebrated cases of people less than an electrical-engineering education using them as a submersion heater to warm up their bathwater, there's an ever-present risk of one accidentally falling into the bathtub, especially if two or more people share a bathroom.

 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Being double-insulated has nothing to do with it.

They're installed because not every bathroom has GFCI receptacles. And not all GFCI's that are installed actually work as intended.


Being double insulated means the case can not become energized, and as such a GFCI would be redundant.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
They might be insulated against incidental contact, but they're not insulated against submersion.

And while there might be one or two celebrated cases of people less than an electrical-engineering education using them as a submersion heater to warm up their bathwater, there's an ever-present risk of one accidentally falling into the bathtub, especially if two or more people share a bathroom.



Right, but do all hair dryers actually have an LCDI plug instead of a GFCI plug? I ask because I've taken apart a few dryers (and their plugs) and while I could be wrong on my judgment I only saw two wires coming from the plug. I can't see how only two wires can sense immersion.

An LCDI would make sense for immersion, but a GFCI may not trip in a sink or bathtub not referenced to earth (plastic drain line)
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
So it saves lives half the time -- especially in the older houses that are least likely to have a GFCI installed. That's better than nothing.
And I suspect most "ungrounded" tubs have enough capacitance to trip a GFCI.


I can't see that level of capacitance being present.
 
Top