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Old 02-08-2012, 10:19 PM   #1
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What would cause a light to flicker? Besides a bad lamp. My friend turns on all the lights in the house and about 10 seconds later they start to have a noticeable flicker.
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Old 02-08-2012, 10:20 PM   #2
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Lots of possible causes. Are they on a dimmer? What type of bulbs?
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Old 02-08-2012, 10:20 PM   #3
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Loose connection in service.
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Old 02-08-2012, 10:41 PM   #4
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bad utility transformer
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Old 02-08-2012, 10:48 PM   #5
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First and foremost he (hire a professional) needs to check everything from the meter to the lighting circuits for loose connections, in particular with the neutral as a loose neutral can result in damaged utilization equipment and/or a fire.

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You need to determine the source, I have posted this many times on ET.

Assuming you do not have a loose neutral or line connection, from the utility to the panel.

Light flicker (dimming and restoration of light to near pre-flicker level) of lights, usually a result of motor starting and the resulting inrush current is a byproduct of several factors and generally is difficult to over come.

AC motor loads (in particular compressors) but all motor loads have inrush currents. These inrush currents result in voltage drop in the branch circuit, panel bus, service laterals, utility transformer and possibility the utility HV feeders.

Flicker is in addition user dependent; some people are more susceptible to flicker. For some reason flicker seems to bother women more that men (based upon personal experience).

A Voltage Drop (VD) as little as 3 volts on a nominal 120 VAC system is noticeable (by me), 2.5% VD.

We have had cases were the VD was all a byproduct of primarily single phase 120 VAC loads, in these cases we were able to put the lighting on L1 and all the motor loads on L2, the HVAC compressors were something the homeowner had to live with. This minimizes the flicker.

To test for this VD and resulting flicker to determine the source of the inrush, use a min max amp clamp and min max multimeter at the main service watch the lights(it may take two workers) and correlate to the meters.


A soft start will minimize the issue.
Putting all lights on one leg and all single phase motors on the other leg will minimize this, though you are in the dumps with 240 vac loads and neutral VD is still present with the single 120 vac loads.
A single phase UPS for a panel feeding all lighting loads would work as well.
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Old 02-08-2012, 11:10 PM   #6
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So I checked the main panel. I found that there is a sub panel also. All the lights are running off the sub panel. I noticed that all the lights are on the red phase.
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Old 02-09-2012, 05:25 PM   #7
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I had a Foreman once tell me to put all the two-pole breakers and any singles pulling heavy motor loads (Such as a Refrigerator or Deep freezer) above the ones feeding any light circuits [Being it's a top fed MB or Main Lug panel]. Said that since the are above them in the panel you won't have any voltage drop causing the lights to dim. It sounds possible but never have tried it.
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Old 02-09-2012, 06:32 PM   #8
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Quote:
Originally Posted by Apprentice_617 View Post
So I checked the main panel. I found that there is a sub panel also. All the lights are running off the sub panel. I noticed that all the lights are on the red phase.
Well there's your problem, you never put lighting loads on the red phase, always use the black or blue phases.
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Old 02-09-2012, 06:35 PM   #9
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Quote:
Originally Posted by Briancraig81 View Post
I had a Foreman once tell me to put all the two-pole breakers and any singles pulling heavy motor loads (Such as a Refrigerator or Deep freezer) above the ones feeding any light circuits [Being it's a top fed MB or Main Lug panel]. Said that since the are above them in the panel you won't have any voltage drop causing the lights to dim. It sounds possible but never have tried it.
That makes perfect sense.....
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Old 02-09-2012, 06:37 PM   #10
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Quote:
Originally Posted by brian john View Post
First and foremost he (hire a professional) needs to check everything from the meter to the lighting circuits for loose connections, in particular with the neutral as a loose neutral can result in damaged utilization equipment and/or a fire.




To test for this VD and resulting flicker to determine the source of the inrush, use a min max amp clamp and min max multimeter at the main service watch the lights(it may take two workers) and correlate to the meters.


A soft start will minimize the issue.
Putting all lights on one leg and all single phase motors on the other leg will minimize this, though you are in the dumps with 240 vac loads and neutral VD is still present with the single 120 vac loads.
A single phase UPS for a panel feeding all lighting loads would work as well.
Brian its a house, probable a loose connection
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