fogless mirror in shower...gfi ?

[Stevenfyeager]

a 24 volt DC, 50 watt 18 ga wire is run into an outlet box behind the UL listed mirror in the shower. The 18 ga wire is run near a switched receptacle for plugging in the transformer. Do you think it is required to be a gfi receptacle? The reason I ask is will the gfi work ok being switched off and on continually? I've not used a switched gfi. We know how sometimes a gfi outlet trips when power is turned off and then back on and has to be reset. Thank you

 

[jumper]

1. If the receptacle is in the bathroom, GFCI protection is required.

2. I am pretty sure that the GFCI receptacle will not protect the mirror via the transformer.

3. I have no clue if the GFCI will trip if switched, never tried.

 

[kwired]

a 24 volt DC, 50 watt 18 ga wire is run into an outlet box behind the UL listed mirror in the shower. The 18 ga wire is run near a switched receptacle for plugging in the transformer. Do you think it is required to be a gfi receptacle? The reason I ask is will the gfi work ok being switched off and on continually? I've not used a switched gfi. We know how sometimes a gfi outlet trips when power is turned off and then back on and has to be reset. Thank you

GFCI that trips when power is cycled is either a portable GFCI device, like those integrated into cordsets that must prove both circuit conductors before the device will reset, or is a result of inductive kickback - sometimes not even originating in the circuit protected.

This low level load probably won't have significant level of inductive kickback.

 

[Unbridled]

XFMR GFCI

XFMR GFCI

Ive never heard of a GFCI Outlet malfunctioning due to switching. I do however know that a GFCI monitors load current on both the ungrounded conductor and the grounded conductor. After a differentiation of a certain percentage of current between the two conductors, the GFCI will trip.
I also believe the induction created by the transformer would be directly proportional to line current, thus not creating enough of a difference in the two conductors to trip the GFCI.
In any regards, a GFCI outlet is required.

Good Luck

 

[kwired]

Ive never heard of a GFCI Outlet malfunctioning due to switching. I do however know that a GFCI monitors load current on both the ungrounded conductor and the grounded conductor. After a differentiation of a certain percentage of current between the two conductors, the GFCI will trip.
I also believe the induction created by the transformer would be directly proportional to line current, thus not creating enough of a difference in the two conductors to trip the GFCI.
In any regards, a GFCI outlet is required.

Good Luck

Correct that line current into transformer is equal to line current returning on the other conductor and that should not cause a problem. What can be a problem with inductive loads is "inductive kickback" when you open the circuit and the magnetic field collapses. Most name brand GFCI's made the past 25 years or so are developed to be resistant to this, but it still happens sometimes when the kickback is unusually high.

 

[Unbridled]

Xfmr Induction

Xfmr Induction

Correct that line current into transformer is equal to line current returning on the other conductor and that should not cause a problem. What can be a problem with inductive loads is "inductive kickback" when you open the circuit and the magnetic field collapses. Most name brand GFCI's made the past 25 years or so are developed to be resistant to this, but it still happens sometimes when the kickback is unusually high.

Kwire,
Is it your opinion the the inductive kickback would create a differential of current between the XFMR'S Line Side grounded conductor and un-grounded conductor when being switched?

Just Curious
Thanks in advance

 

[kwired]

Kwire,
Is it your opinion the the inductive kickback would create a differential of current between the XFMR'S Line Side grounded conductor and un-grounded conductor when being switched?

Just Curious
Thanks in advance

Well in theory both conductors are carrying the same current, but this particular situation is a little more complex and I am not really sure exactly what it going on. You do have to remember when the magnetic field collapses it can produce voltage in the thousands of volts range, but there is little power behind it so it is at low current. Old point/condenser ignition systems on old internal combustion engines took advantage of this to create the spark for ignition.

 

[Coppersmith]

a 24 volt DC, 50 watt 18 ga wire is run into an outlet box behind the UL listed mirror in the shower. The 18 ga wire is run near a switched receptacle for plugging in the transformer. Do you think it is required to be a gfi receptacle? The reason I ask is will the gfi work ok being switched off and on continually? I've not used a switched gfi. We know how sometimes a gfi outlet trips when power is turned off and then back on and has to be reset. Thank you

If I understand you correctly, you want to trip the GFCI in order to switch the mirror on and off. Why not just add a switch/receptacle combo on the load side of the GFCI? That way you never have to trip the GFCI.

 

[kwired]

If I understand you correctly, you want to trip the GFCI in order to switch the mirror on and off. Why not just add a switch/receptacle combo on the load side of the GFCI? That way you never have to trip the GFCI.

If I understand correctly the receptacle in question is already controlled by a switch, he is just asking if GFCI protection is required. If the receptacle is in the bathroom the answer is all 15/20 amp 120 volt receptacles in bathrooms must have GFCI protection. If it is not in the bathroom, my answer is maybe.