Symptom - what's your explaination?

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bjp_ne_elec

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Let's say you have a 120 volt circuit that feeds various incandescent lights and the brightness of the bulbs that happen to be turned on - their brightness varies dependant on which light is turned on (not an actual issue I'm having - but have seen it posed as question). What's your thought on what issue could cause this?

Thanks

Brett
 
Re: Symptom - what's your explaination?

Open or poorly connected neutral conductors in ether a multiwire branch circuit, feeder or service.
 
Re: Symptom - what's your explaination?

Concure, usually high resistance on neutral connection at breaker panel or line to service transformer.

Think of neutral as a center tap on a 240 vac transformer so each side has 120 vac to center tap. If there is resistance in the neutral connection to transformer then as more load is applied to one side its voltage drops and the other side with ligher load voltage goes up, sum of two = 240 vac.

Blows out light bulbs and really bad on refrigerator compressors.
 
Re: Symptom - what's your explaination?

I don't understand the question. Which of these are you trying to describe:
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">If you look only at one light, and start with that one on and all others off, and if while looking at that light a friend starts turning on other lights, then the brightness of the light you are looking at will change as each other light is turned on. Then you start the experiment again, this time starting by looking at a different light, and starting with all others turned off. You do the experiment for each light, and see the same change in brightness no matter which light you are looking at, when you turn on the other lights.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">OR
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">If you turn on all the lights, and walk around, you will see that each light has a different brightness than each other light. But then if you look at one light, and your friend starts turning off the others, the brightness of the one you are looking at does not change.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">Or is it something else?

If it is the first version, then you might have two or more of the lights in series, and not (as they should be) in parallel. If it is the second version, then the simplest explanation is that the bulbs have different ratings (e.g., you have a 40, a 60, a 70, and a 100 watt bulb in the different fixtures).
 
Re: Symptom - what's your explaination?

If you have only one circuit serving these various lights as idicated in your post, perhaps you are experience voltage drop with all lights on which is reduced as each light on the circuit is turned off. I doubt it could be noticed however. :confused:
 
Re: Symptom - what's your explaination?

charlie b - the way I was asking it, was just staying with one light in particular room. Dependant on which room, and therefore which light got switched on, the brightness of the "one light in the particular room" would change - and again, the brightness would vary dependant on which order and which room was switched "on" or "off". The lights are all assumed to be on one of the two legs of the 120/240V multiwire circuit.

[ January 30, 2006, 05:56 PM: Message edited by: bjp_ne_elec ]
 
Re: Symptom - what's your explaination?

Dependant on which room, and therefore which light got switched on, the brightness of the "one light in the particular room" would change
Click to expand...
Maybe a series-parrallel circuit, with the variable-voltage bulb wired in series to the parallel-bulb array.

Edit: But, the series switch or bulb-filament life would control the entire circuit.

[ January 31, 2006, 11:11 AM: Message edited by: ramsy ]
 
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