can i detect if the hot and neutral lines reversed?

ebp

Joined Feb 8, 2018
2,332
Yes, I can see a potential (yes, I said that deliberately and apologetically) issue if the only access to connect the lamp to the circuit is a single wire with the connection to the other side of the lamp unknown - which would be singularly weird in my experience, but perhaps the sort of thing encountered in some countries.

There are little test tools available that will distinguish "hot" from "neutral" in most circumstances if neutral is reasonably close to ground potential. e.g. Fluke 1AC-A1-II
 

Thread Starter

Layan_AK

Joined Mar 28, 2017
78
Hi all..

Sorry for being late ..

My circuit in the post was not clear sorry for that .. I thought when I said the lamp already connected to neutral enough to describe what I need ..

Btw the following figure describe my circuit ..
20180730_224308.jpg

Changing the lamp terminal which pre connected to neutral is difficult to me .

Thank you for your appreciated effort:)
 

ebp

Joined Feb 8, 2018
2,332
The question that still remains is how to handle this. Is it sufficient to try to identity which is "hot" and which is "neutral" at installation time or must the circuit determine that automatically and make the required connection accordingly?
 

Thread Starter

Layan_AK

Joined Mar 28, 2017
78
The question that still remains is how to handle this. Is it sufficient to try to identity which is "hot" and which is "neutral" at installation time or must the circuit determine that automatically and make the required connection accordingly?
If the circuit determine that and give message indicating the wrong connection enough ^^

Regards
 

Thread Starter

Layan_AK

Joined Mar 28, 2017
78
You mean like this ?

1532989143704-1271873128.jpg

If yes it will light even the lamp exist ?

The type of lamp will affect ?

Regards
 
Last edited:

WBahn

Joined Mar 31, 2012
26,398
Do you NEED to know that the L and N are swapped, or will you be happy if the circuit simply works whether they are swapped or not?

If the latter, then just use two suitable diodes to do something like the following:

20180730_224308.jpg

This will provide a half wave rectified voltage to the lamp, so the brightness will be about half what it would normally be (which the human eye has a hard time noticing).
 

AlbertHall

Joined Jun 4, 2014
11,100
just use two suitable diodes to do something like the following:
But now it does depend on what kind of lamp it is.
LED, CFL will probably work just fine and full brightness.
Incandescent will be half brightness.
A halogen lamp fed by a transformer would blow the fuse.
A fluorescent strip light with inductive ballast would probably do very bad things.
 

WBahn

Joined Mar 31, 2012
26,398
But now it does depend on what kind of lamp it is.
LED, CFL will probably work just fine and full brightness.
Incandescent will be half brightness.
A halogen lamp fed by a transformer would blow the fuse.
A fluorescent strip light with inductive ballast would probably do very bad things.
I was assuming that it was an incandescent lamp -- but that may have been a bad assumption.

@Layan_AK : What kind of lamp are you using?
 

WBahn

Joined Mar 31, 2012
26,398
But he can't do that because he does not have access to one side of the lamp which is already wired to the neutral conductor.
 

sdowney717

Joined Jul 18, 2012
648
Lamps should have physical polarized plugs, then assuming the device plugged into is wired correctly, everything is fine.

This whole thread seems odd to me, plugs and pluggable devices are made to line up neutral and hots appropriately.
 
Lamps should have physical polarized plugs, then assuming the device plugged into is wired correctly, everything is fine.

This whole thread seems odd to me, plugs and pluggable devices are made to line up neutral and hots appropriately.
Maybe American outlets do. Here in the Netherlands our outlets are not polarized.
 

MrAl

Joined Jun 17, 2014
8,063
Hello,

Sometimes the lines can get swapped anyway.

The only way to be sure is to locate a ground connection. Measure both hot and neutral to that ground. If the neural is really the hot line then you will find that out quickly.

A DPDT or DPST relay or switch would work, but sometimes you need the hot and neutral to be CORRECT even when the switch or relay is turned on, so that wont help in that case either.
 
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