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Old 02-24-2012, 02:41 PM   #1
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Default House Lights flicker

I have a 10 Year old house. The last 3 months i have noticed that all the lights are flickering at a regular interval. The basement lights, on a separate circuit, main living room, bedrooms...anyway you get the picture. They DIM for about 0.5s. It used to be at a regular interval of 10 minutes but recently seems to be less than that but still regular. I have removed the following circuits either VIA a breaker or by unplugging them. Detached garage, well pump, air conditioner, refrigerators, freezer, AC, microwave, TV and the lights continue to flicker/DIM. Since the lights are on separate circuits and none of the disconnected loads made a difference i called out the electric company. They put on a recorder and said they didn't see anything wrong. So i took home a fluke meter and did some measurements for myself. On both phases i see a 3V change (same thing electric company saw) in the average RMS voltage to the house. I have checked both phases on either side of the breaker as well and the same 3V change is all i see. The meter records events that last at least 100ms. So first question, is 3Vrms enough to see with the naked eye? If 3Vrms is enough, what could be causing the lights to flicker if it isn't the service? I have checked for loose connections in the panel and didn't find any.

Thanks.

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Old 02-24-2012, 06:02 PM   #2
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Quote:
Originally Posted by 70Vette69 View Post
I have a 10 Year old house. The last 3 months i have noticed that all the lights are flickering at a regular interval. The basement lights, on a separate circuit, main living room, bedrooms...anyway you get the picture. They DIM for about 0.5s. It used to be at a regular interval of 10 minutes but recently seems to be less than that but still regular. I have removed the following circuits either VIA a breaker or by unplugging them. Detached garage, well pump, air conditioner, refrigerators, freezer, AC, microwave, TV and the lights continue to flicker/DIM. Since the lights are on separate circuits and none of the disconnected loads made a difference i called out the electric company. They put on a recorder and said they didn't see anything wrong. So i took home a fluke meter and did some measurements for myself. On both phases i see a 3V change (same thing electric company saw) in the average RMS voltage to the house. I have checked both phases on either side of the breaker as well and the same 3V change is all i see. The meter records events that last at least 100ms. So first question, is 3Vrms enough to see with the naked eye? If 3Vrms is enough, what could be causing the lights to flicker if it isn't the service? I have checked for loose connections in the panel and didn't find any.

Thanks.
How can you be seeing such a small change in voltage ?
a change of 3v amounts to only 2.5% on a 120v supply.
well within tolerances.
In australia tolerance is +10% to -20%.
If yours is simulair, then it is well within specs.
What type of lights do you use ?

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Old 02-24-2012, 06:46 PM   #3
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Electric water heater?
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Old 02-24-2012, 06:49 PM   #4
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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.

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.

WHAT I POSTED PREVIOUSLY

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.

Last edited by brian john; 02-24-2012 at 06:51 PM.
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Old 02-24-2012, 06:49 PM   #5
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Quote:
Originally Posted by dmxtothemax View Post
How can you be seeing such a small change in voltage ?
a change of 3v amounts to only 2.5% on a 120v supply.
well within tolerances.
In australia tolerance is +10% to -20%.
If yours is simulair, then it is well within specs.
What type of lights do you use ?
2.5% is more than sufficent to notice light flicker.
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Old 02-27-2012, 08:35 AM   #6
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I have a gas water heater not electric. So I understand a loose connection could cause this issue but there are two things that don't make sense about a loose connection. 1. It is predictable, i.e. every 10 minutes, not random. 2. I see the lights flicker on two separate circuit feeds. This means that if it was a loose connection it would have to be in the panel itself and the electric company and I independently have looked at the box for loose connections and didn't find any. I have shut off the breakers and/or unplugged all AC motors and anything that would draw a heavy load and the lights still flicker. Seems to me that the issue is the feed to my house.....i guess the only way to really know is to shut off the main breaker and see if i can still see the voltage drop on the feed to the house.

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