knob and tube wiring and led lamps

[domnic]

My neighbor lives in a 100 year old house. he replaced a incandescent lamp with a led lamp.in the bedroom in the upstairs of his house. their is some knob and tube in the upstairs . the new led did not work tried a another led same did not work. so I looked at it. I found the polarity reversed. so I changed the polarity at the fixture. works fine now. are all led lamps made this way ?

 

[jumper]

Yes, LEDs-Light Emitting Diodes- are polarity sensitive.

http://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/special-purpose-diodes/

 

[al hildenbrand]

My neighbor lives in a 100 year old house. he replaced a incandescent lamp with a led lamp.in the bedroom in the upstairs of his house. their is some knob and tube in the upstairs . the new led did not work tried a another led same did not work. so I looked at it. I found the polarity reversed. so I changed the polarity at the fixture. works fine now. are all led lamps made this way ?

While the actual light emitting diode is a specialized form of a diode the conducts current only in one direction, making it a polarized element of the circuit, it is required to work at a voltage much lower the normal 120 Volt AC that one finds on an existing Knob & Tube lighting outlet. An intermediate circuit, a driver, must be used to limit 120 Volt AC voltage and the current flowing in the actual light emitting diode.

It doesn't make sense that the "driver" would be sensitive to whichever Knob & Tube conductor is energized, especially because there usually is no Equipment Grounding Conductor present.

 

[ptonsparky]

Yes, LEDs-Light Emitting Diodes- are polarity sensitive.

http://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/special-purpose-diodes/

Ok, LEDs are polarity sensitive. What does that have to do with which conductor Is switched to its power supply?

Edit: or in this case if one of the conductors is grounded and switched as they were frequently in K&T wiring.

 

[kwired]

Yes, LEDs-Light Emitting Diodes- are polarity sensitive.

http://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/special-purpose-diodes/

LED components in said lamp are polarity sensitive, AC input to the driver is still ~ 120 VAC regardless of polarity of the AC line.

I think there is more to the OP's situation then he has told us or even realizes.

 

[domnic]

led polarity

led polarity

Since my last post in my shop I tried four different led lamps. with reverse polarity all worked fine. maybe I hade a pack of bad lamps ?

 

[hbiss]

I think there is more to the OP's situation then he has told us or even realizes.

I agree. Hot and neutral reversed shouldn't make any more difference than with a regular incandescent light bulb.

-Hal

 

[Open Neutral]

Since my last post in my shop I tried four different led lamps. with reverse polarity all worked fine. maybe I hade a pack of bad lamps ?

re: reversal:
Do you mean the K&T line to the LED power supply?
or
The power supply to the LEDs?

 

[GoldDigger]

re: reversal:
Do you mean the K&T line to the LED power supply?
or
The power supply to the LEDs?

Reversal means exchanging the connections of the hot and neutral (grounded) line to the equipment.
Whether K&T or any other wiring for test purposes.

 

[Electric-Light]

The process of correcting reversed wiring most likely corrected loose connections. Perhaps connections in the socket is loose.

 

[Open Neutral]

Since my last post in my shop I tried four different led lamps. with reverse polarity all worked fine. maybe I hade a pack of bad lamps ?

re: reversal:
Do you mean the K&T line to the LED power supply?
or
The power supply to the LEDs?

 

[Electric-Light]

re: reversal:
Do you mean the K&T line to the LED power supply?
or
The power supply to the LEDs?

He's using an LED lamp with a built-in disposable ballast like CFL.

My neighbor lives in a 100 year old house. he replaced a incandescent lamp with a led lamp