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Lights dim when printer, vacuum cleaner or even TV is turned on in new house

Lights dim when printer, vacuum cleaner or even TV is turned on in new house

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  #1  
Old 02-28-18, 06:02 PM
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Unhappy Lights dim when printer, vacuum cleaner or even TV is turned on in new house

I bought a new house last year and am within a one-year builder warranty period.

My tenant has reported that the lights dim momentarily when her printer starts in one room or, more recently, even when she turns on a TV in a bedroom on the other side of the house. My wife recalls seeing the dimming when she turned on a vacuum cleaner last summer, and an electrician who looked into this for the builder said he had seen the same phenomenon with a vacuum cleaner at another new house.

I don't think this should be happening, especially in a new house. The builder's electrician did not seem especially knowledgeable about the physics of the dimming phenomenon, and he wanted to attribute it simply to the printer drawing more current at startup. The breaker never trips, although several months ago another electrician replaced a faulty breaker for the air conditioner.

When I asked the electrician for a better explanation of the lights dimming, he speculated that the new arc-fault breakers may be more susceptible than older breakers to whatever condition causes the dimming. I doubt that, but is there anything about arc-fault breakers that might make the dimming more likely?

All this doesn't seem right, especially in a new house. I am looking for a better explanation and, particularly, for something I can ask the builder to do. I live far away from this house but I will be the area in the summer and can do some testing on my own before the warranty ends.

In an older thread on this forum, the dimming of lights was attributed to loose connections at devices along the path from the breaker to the lights that dim. Is that the only explanation? Is there any good way to trace the path or verify the problem, short of a trial-and-error process of opening up every outlet, fixture or switch box, probably disconnecting any quick-connects and tightening wires under screws?

I suspect that a single loose connection is unlikely as the cause, because my tenant's TV in one room probably is not on the same circuit as the printer in the other room. If I were there to test, I might try running an extension cord from the printer to outlets in several rooms to see if the problem occurs consistently on multiple circuits.
 
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Old 02-28-18, 07:15 PM
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My tenant has reported that the lights dim momentarily when her printer starts in one room or, more recently, even when she turns on a TV in a bedroom on the other side of the house.
If they have a laser printer, it is considered normal because laser printer pulls a lot of current at startup heating up the fuser. The only good way to avoid this is to separate lighting and outlet circuits.
TV shouldn't cause problem unless they are using old CRT, which also has high starting current.
Vacuum cleaners also pull high current and light dimming slightly is normal.

If the light dims more than usual and even with light loads, it is possible there is a loose connection somewhere. Will have to check every single splices on the circuit to be sure.

he speculated that the new arc-fault breakers may be more susceptible than older breakers to whatever condition causes the dimming.
It may cause false positive trips, but not dimming lights.
 
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Old 02-28-18, 07:17 PM
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If the wire were loose in the panel or outside the house it could affect multiple circuits.
 
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Old 02-28-18, 08:31 PM
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When I wire a house.... the lighting is all on it's own circuits. No receptacles are on the lighting circuits. This way a heavy start up load is not as noticeable. As mentioned.... a laser printer and vacuum are very high current inrush items on starting. Some dimming is normal. If you have receptacles and lighting mixed.... expect some dimming.

If you are any distance from the electrical transformer.... the dimming under heavy load is more noticeable.
 
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Old 03-01-18, 04:32 AM
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If they have a laser printer, it is considered normal because laser printer pulls a lot of current at startup heating up the fuser.....
Vacuum cleaners also pull high current and light dimming slightly is normal.
If the current draw is not enough to trip a breaker but the dimming is "normal," then wouldn't it be logical that, if you have a heavily loaded circuit -- let's say toaster, coffee maker and counter-top microwave operating at the same time, for lack of a better example -- wouldn't any light on the circuit be continuously dim?

What is the physics involved in dimming the lights? Does voltage on the circuit drop? Are appliances or home electronics endangered by this condition, even though there's nothing to see?
 
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Old 03-01-18, 05:21 AM
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if you have a heavily loaded circuit -- let's say toaster, coffee maker and counter-top microwave operating at the same time, for lack of a better example -- wouldn't any light on the circuit be continuously dim?
Yes it will. That is why kitchen counter outlets are on their own circuit. They are never shared with lighting circuit.

What is the physics involved in dimming the lights? Does voltage on the circuit drop? Are appliances or home electronics endangered by this condition, even though there's nothing to see?
Yes, the voltage drops. In my room, voltage drops from 120V to near 100V when my laser printer kicks on and the light flickers.
This is causing my UPS to kick on time to time, but not much I can do without pulling new cable.

Usually this will not damage any electronics, but some electronics are more sensitive then others.
 
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Old 03-01-18, 05:26 AM
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I am certainly not saying this is what the problem is but in my house I had the same problem. Recently I upgraded my breakers to AFCI/GFCI ones and during the process I realized almost 95% of my old breakers were wired up very badly where eevery breakerís neutral was grouped with 2 other breakers (so 3 neutrals in 1 pigtail). To make matters worse, 14 ga pigtail was used everywhere including 20amp circuits. Also more than half of the bus bar connections were not tight. Once I replced all my breakers and fixed these pigtails and organized everything, all that dimming disappeared. Even when my a/c compressor kicks in now the lights dont dim. So I wouldnt dismiss badly formed connections or overloaded circuits.
 
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Old 03-01-18, 01:42 PM
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A drop (from 115-120 volts) down to 100 volts when a household small appliance or computer or TV is turned on is abnormal.

There is a loose connection somewhere or, worse, a missing or broken neutral which can lead to overvoltage elsewhere in the house.

Where there is resistance in a circuit, voltage is dropped within the resistance and can be measured by touching the voltmeter probes before and after the resistance respectively. Normally the power feed has negligible resistance from the source (here, the utility pole transformer) up to the light or appliance or other load and negligible resistance from the load back to the source. So practically all of the 120 volts are dropped across the intended load which condition represents the most efficient and best used of power.

A loose connection introduces resistance and heat (which represents waste) is generated at that point when current flows through if it can at all. In addition the reduced voltage remaining for the light or other desired load results in poorer performance of the light or desired load.

Ohms Law applies to all circuits. At all times in any portion of any circuit the voltage dropped across that portion equals the current flowing at that moment times the resistance of that portion. Some special calculations using what are called complex numbers, usually taught in "algebra II" in high school, are needed to accurately determine the behavior of alternating current circuits.
 
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Old 03-01-18, 03:51 PM
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A drop (from 115-120 volts) down to 100 volts when a household small appliance or computer or TV is turned on is abnormal.
If you are talking about my case, it is drop from a initial surge. Not continuous voltage drop. Continuous voltage is around 115 to 117V under load. At least that is why my UPS is reading.
 
 

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