GFCI Thingy on Hair Dryers

[mbrooke]

Why do hair dryers have a GFCI plug considering the dryer itself is double insulated?

..................

 

[LarryFine]

Probably because of use near sinks.

 

[mbrooke]

Probably because of use near sinks.

???

The dryer is double insulated. A lower body resistance would make no difference.

 

[ppsh]

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.

 

[mbrooke]

From a UL document.

So the thing on hair dryers is an IDCI? Why don't I always see a 3rd sensor wire going to the dryer? And what caused people to be concerned about immersion?

 

[rnatalie]

Because idiots use them in the bathtub.

 

[mbrooke]

Because idiots use them in the bathtub.

That was actually a thing?

 

[LarryFine]

That was actually a thing?

Yep. Every time they try to make thing safer, along comes a group of new-and-improved idiots.

 

[480sparky]

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]

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]

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]

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)

 

[480sparky]

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

Until it becomes immersed.

 

[mbrooke]

Until it becomes immersed.

In which a GFCI would do nothing if the person was immersed in an ungrounded bath tub.

I only have doubts because I've taken plugs apart which appeared to be GFCI vs LCDI.

 

[480sparky]

In which a GFCI would do nothing if the person was immersed in an ungrounded bath tub......

But could 'do something' as soon as the person touched something (even somewhat) grounded.

 

[mbrooke]

But could 'do something' as soon as the person touched something (even somewhat) grounded.

Correct.

 

[drcampbell]

In which a GFCI would do nothing if the person was immersed in an ungrounded bath tub. ...

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.

 

[mbrooke]

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.

 

[bwat]

But could 'do something' as soon as the person touched something (even somewhat) grounded.

Correct.

I’d think the tub faucet, handle, or tub drain switch/lever could be good candidates for this.

 

[mbrooke]

I’d think the tub faucet, handle, or tub drain switch/lever could be good candidates for this.

In theory yes. But an LCDI would cover everything.