What is this?

[Terry A. Tucker]

The home was built in 2007 and I have no idea what this thing is. It appears to be a light fixture but has a fuse inserted. It is located inside a bedroom closet. Any ideas?2837528376

[Jerry Peck]

That is someone totally screwing things up.

The keyless lampholder had a fuse screwed into it to protect the low voltage transformer mounted behind the lampholder.

Not sure if there is *anything* which might be right in that photo ...

[Garry Sorrells]

The light fixture is acting as a pass trough to the transformer. Fuse is inline to the transformer.

[Terry A. Tucker]

Okay, but what is the function of the transformer? Why is this thing in my closet?

[John Kogel]

A transformer in a closet in my area is likely for the doorbell ringer. Those wires going back in thru the lamp holder are low voltage and will be going to the doorbell unit, which is often mounted in the hallway. Or possibly to some other low voltage device like an alarm or a thermostat. Those low voltage wires are not required to be concealed or protected.

We don't know the function of the fuse. It could just be there as a plug to keep someone from getting a shock. The transformer doesn't need the fuse, because it is in all likelihood on a circuit which is protected by a breaker in the electrical panel.

Unscrew the fuse and see if the doorbell still rings or the thermostat still operates. It probably will. Replace the lamp holder with a simple round cover plate. If the fuse is inline with the transformer, get an electrician to rewire that connection, and then have him inspect the rest of the house, especially the main panel.

[Terry A. Tucker]

I unscrewed the fuse and the doorbell did not ring. Not sure why I didn't think to try that before as I had always suspected it may be for the door bell located in the adjacent hall.
Thanks for the help!

[John Kogel]

I unscrewed the fuse and the doorbell did not ring. Not sure why I didn't think to try that before as I had always suspected it may be for the door bell located in the adjacent hall.
Thanks for the help!It is an unconventional way to wire the doorbell ringer, so probably done by an old school handyman.
FYI, the transformer must be installed in an accessible place, so that is why we see them in closets. That part at least is correct. The fuse is redundant.

[Rick Cantrell]

The low voltage wires are not allowed to enter the box where house wiring is located.

[John Kogel]

The low voltage wires are not allowed to enter the box where house wiring is located.Thanks, Rick, good point.

Stupid stuff can distract us from seeing the other stupid stuff. That one got me. :biggrin:

[Jerry Peck]

The low voltage wires are not allowed to enter the box where house wiring is located.

One of the reasons I said:

Not sure if there is *anything* which might be right in that photo ...


Type 2 transformers are current limited so if that 15 amp fuse is on the LV side it would never open even if the transformer secondary were dead shorted.

I doubt the fuse is on the low voltage side, I suspect it just looks that way. I suspect that the line side is run through the fuse and the low voltage cable is just visible because it was small enough to run through the unused mounting screw hole and through the lampholder to 'wherever' it goes (we do not even know for sure that it goes back into the junction box, the low voltage cable could just go in through the screw hole and then over the edge of the box - which would still make it 'within' the 'confines' of the box had a proper cover been placed over the box even though it may not actually be 'in' the box. Just not enough information shown in those two photos to specifically state that.

But it can be stated that we are "Not sure if there is *anything* which might be right in that photo ... "

[Mike Clarke]

Grew up on a farm, grandfathers, still in the family, first in the county to have electric installed and they did all the wiring themselves and had a good many number of the porcelain lamp sockets used as fuse holders. They had many different livestock and before the big chain stores was one of the areas largest poultry producers many decades ago. They had wired electric lighting on timers to simulate extended daylight hours, My grandfather was one of those inventing types, had to since never had enough money (or never wanting to spend it anyway) on buying what he needed. There are a few buildings remaining, one still has the old fuses for lighting, still working. I will have to say they were neat about the installations and never an issue.
Really brings back the memories every time I see something that makes me relate back to the farm.
However not the best idea as the outer case on the socket is too exposed, usually the nutral side when wired for lighting, but to acceptable for usage as a passthrough device.
Reminds me, Going to talk to my brother about those on the farm still working, needs to go.

[Phillip Stojanik]

Have to admit that it is an intriguing use of the involved materials.

[Mbrooke]

Have to admit that it is an intriguing use of the involved materials.


I agree. I know I'm commenting now but I just came across this.

It doesn't look that bad to me. If the transformer decides to grenade in that closet there will be a lot less carnage with the inline fuse. Other than 1 or two possible NEC violations its actually a nifty idea. In theory its safer than the direct tap method; It looks like the fuse is there to protect the transformer from a violent failure and from taking down the whole circuit should it fail internally. The fuse is 3 amps by the way.

Now personally I have never seen one fail in sparks, but I guess the installer might now something.

Not saying this shouldnt be evaluated by an electrician, but in Europe the norm is to individually protect bell transformers:

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[Mike Clarke]

Have not yet run across DIN rail devices being used in residential in the US, mostly commercial.
However, thought that would not be allowed to have high and low voltage in the same box without some sort of separation ?

Also, They do make specific fuse sockets for locating at devices that are safer to use (if still using fuses) than using a standard lamp socket which is unsafe for that purpose.

[Mbrooke]

Have not yet run across DIN rail devices being used in residential in the US, mostly commercial.
However, thought that would not be allowed to have high and low voltage in the same box without some sort of separation ?

Also, They do make specific fuse sockets for locating at devices that are safer to use (if still using fuses) than using a standard lamp socket which is unsafe for that purpose.

DIN rails are the norm in Europe for nearly all new electrical installs. I cant speak for all of Europe but different codes apply to the separation of high and low voltages than the U.S.

[Mike Clarke]

DIN rails are the norm in Europe for nearly all new electrical installs. I cant speak for all of Europe but different codes apply to the separation of high and low voltages than the U.S.

Every time I go to Europe for a visit, amazed how there are many things done better than in the US, not that familiar with the electrical stuff over there but there are many things have got way ahead of us in the US.
I am really interested now in learning more about way things are done in the building industry there.

[Mbrooke]

Every time I go to Europe for a visit, amazed how there are many things done better than in the US, not that familiar with the electrical stuff over there but there are many things have got way ahead of us in the US.
I am really interested now in learning more about way things are done in the building industry there.


In my opinion you are right. Europe has better and tighter regulations then the US. RCD (GFCI breakers) circuits have been required on most circuits some time now. There system is fascinating no doubt.

If your interested in learning more there is a guy called "Frenchelectrician" who is a moderator and posts on electrician talk.com. He knows his stuff really well. You could sign up and PM him if your interested in this stuff.

[H.G. Watson, Sr.]

Unlisted, non-field evaluated, use, rigged transformer, plastic luminaire, and edison fuse in same, not a listed "power supply", unclassed, use of componant part, not "equipment", not "listed equipment", not a "listed system" to direct wiring to componant (recognized or not) transformer.

WAG 24 or 12V AC or perhaps even 48V or 50V, DIY hack work. The unlisted/non-classified raw step-down transformer (not complete power supply!!) is not compliant in its install (NEC) is an inductive load and open wiring (input terminals are pictured) and unprotected (no cabinet) as it is in a storage area or clothes closet, esp. not open hard wired & exposed (unprotected from incidental contact - assuring free air) and NOT as an unclassified (listed complete) power supply - its just a raw transformer, inappropriately hard-wired.

The raw transformer (not "power supply") is hard wired to 120VAC via an inappropriately modified luminaire/light fixture with power from the panel likely a 15 or 20A circuit, which has been inappropritely further modified and installed a 3A fuse in an unlisted manner, and is stepping down to 12, 18, 24, 30, 48, 50, VAC or whichever voltage AC and unknown KVA.

There is no appropriate means to disconnect, unscrewing an edison fuse from a lamp holder is not appropriate. (approved disconnect switch or blade/cap from receptacle disconnect means are required).