Pulsating lights

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  #1  
Old 12-31-12, 11:01 AM
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Pulsating lights

Hello- we recently moved into half of a duplex. The structure is circa 1970's. There is a meter and circuit box for each side (so I assume the wiring is completely separate between the two halves).
Whenever ANY motor load is applied, on any circuit in my house, and I think on the other side also (like when the neighbor runs their dishwasher), the lights all pulsate. Not just lights on the same circuit as the motor load, but all lights on all circuits. I suspect the voltage is irregular but do not know the cause. None of the circuits ever trip a breaker. The worst is with the treadmill on, because it is the largest motor load, but microwave, dishwasher, and furnace blower also causes it.
I suspect voltage irregularity because when the microwave is turned on my computer switches on its battery backup and the cause is listed in its logs as "voltage irregularity".. some days show it being switched on many times.)
So i suspect, and see online, that this is not a good thing for electronics.
Should I tell my landlord he needs to get it checked by an electrician? Any suspect causes?
 
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Old 12-31-12, 11:54 AM
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Some brief dimming when large loads startup is normal in most residential settings. It sounds like you have a bit more of an issue though when you're talking about your lights pulsing while the appliances run. I would think this might have to do with a really old service. My first thought is that you're nearing the limit of what the transformer/service wires/main breaker can handle.

Others may have other suggestions, but you may want to take a picture and post it of the service entry wires and meter. We can get a better idea if that may be the issue.
 
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Old 12-31-12, 12:15 PM
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Akrbt, please add your location to your profile so we will know if you are in the US. If this is a rental you need to contact your landlord to have this checked out by licensed electrician. This is not a handy man or supper job.
 
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Old 12-31-12, 05:32 PM
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more information on my situation

I am in Anchorage, Alaska.

The lights definitely pulse the whole time when motor or other heavy loads (like the microwave, but interestingly not the electric range that we have noticed yet?) are applied, even if not on same circuit as the lights pulsating. Example, wife running on treadmill in basement... all lights in the house pulse, including Christmas lights. It is less noticeable but still present when dishwasher, microwave, washer, dryer, and furnace fan are going.

I do have information on this half of the duplex's circuit breaker panel. It is a Murray LC016DF, it says 125 amp max. All breaker panels are filled- there are twelve 20 amp circuit breakers, and one 50 amp and one 30 amp circuit breakers that take up two sections each. Now my math and understanding of electrical circuits is not that good, but if each of these circuits was operating at nearly full load it would be approaching 320 amps?! But no individual circuit breakers would pop unless one of them was over loaded, correct?
 
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Old 12-31-12, 05:55 PM
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I get the same pulsating when running my 120 volt air compressor in the garage, but at no other time. I first noticed it when my 200 amp service and garage subpanel were new. I always attributed it to living in an older area with too many homes (5 or 6 I think) on the same transformer and older overhead utility wiring.
 
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Old 12-31-12, 05:58 PM
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if each of these circuits was operating at nearly full load it would be approaching 320 amps?! But no individual circuit breakers would pop unless one of them was over loaded
Will never happen, you don't have that much actual load. You probably have either a 125 amp breaker or 125 amp fuses at the meter socket outside that protects your service panel.
 
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Old 01-01-13, 01:37 AM
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......but interestingly not the electric range that we have noticed yet?
You may have a problem with the neutral.
The range is 240 v and doesn't use the neutral for any heavy loads.
 
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Old 01-01-13, 06:32 AM
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Adding up the breaker handles totally ignores the fact that a 20 amp circuit could only have a turned off coffee pot on it using a digital clock or that not everything is in use at the same time like heat and air conditioning.
 
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Old 01-01-13, 11:00 AM
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The lights definitely pulse the whole time when motor or other heavy loads (like the microwave, but interestingly not the electric range that we have noticed yet?) are applied, even if not on same circuit as the lights pulsating. Example, wife running on treadmill in basement... all lights in the house pulse, including Christmas lights. It is less noticeable but still present when dishwasher, microwave, washer, dryer, and furnace fan are going.
Depending on how the lights and receptacles in your duplex are wired, you might be able to minimize this effect by separating them relative to the two legs of your service. This worked for me when I rewired an older house for us and ran into the same problem.

If the lights are on their own circuits and the receptacles are on different circuits, you can move the lighting circuits to be on Leg A, for example, and the circuits that feed motor loads to be on Leg B. Leg A is circuits 1, 2, 5, 6, 9, 10, 13 and 14. Leg B is circuits 3, 4, 7, 8, 11, 12, 15 and 16. (The easy way to remember this is to remember that every even-numbered breaker whose position number is evenly divisible by four is on leg B, and the breaker to its left, with the next lower number, is too; the other breakers are all on Leg A.)

One other thought: I couldn't find any specs online for your panel, so I don't know whether this applies or not, but -- if your Murray Crouse-Hinds load center is a split-bus panel, then making sure that the 240V loads and the 120V loads are each in their designated sections can make a big improvement in reducing harmonic interference. Since your problem seems to be coming from motor loads on 120V circuits, this is less likely to help in your situation, so just a thought.
 
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