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Blinking Lights

My lights are blinking and my UPS for my computer is beeping. I had the electrict company monitor my input (didnt do it while the logger was attached)and they say it is steady on both lines. I used a multimeter and when the blink occours it shows the voltage drops from 120 to around 100 and returns. The interval between these drops is random. I have had an electrician check all connections and all are tight and the breakers are not warm.

It is annoying and frustrating. I am looking for any ideas as to what the problem may be.

Re: Blinking Lights

You didnt really give us enough info to do anything other then guess. I know this is a DIY thread but something like this requires a diagnostic that involves working with live parts some of which can not be powered down, inherently requireing arc flash protection. for those reasons in my opinion this one should be left to a pro. but i can tell you what I think the pro should do.

unplug EVERYTHING (or at least everything you want to keep)
Load test.
Using a drill motor or even an electric heater. I would put a load on each phase incoming (individually)and test with respect to both the grounded and grounding conductors (nuetral and ground) at each point on the service (weather head, line side of the meter, load side, disco, lugs, main breaker, breakers subs etc) all the way to the point at which i noticed it first recording my results. If I was unable to recreate it that way I would increase the load slightly and do it again untill i found it. Very rarely will you not find the drop with a good 4 or 5 amp load on it.

also important to note the voltage between phases and from the no load phase with respect to grounded and equipment grounding conductors at each test point.

Re: Blinking Lights


If there is a sufficient amp draw it will cause a voltage drop. Check to see if there is a large appliance (washer, dryer, refrigerator) kicking on at the same time. One of these could be your culprit.

Hope this is of some help to you and good luck.


Measure once, Cut twice

Re: Blinking Lights

Sorry I wasnt too specific. I have underground service coming in on aluminum conductors. My house is approximately 150 feet from the transformer. I turned off all the breakers in the main and sub-panels. I connected a pig tail light to each leg on the incoming lines at the meter in turn and turned on each breaker in turn. I still had the same random blink with all circuts off on each line. My idea was that one of the major culprits was a refridgerator, freezer, or the HVAC unit. That is why I contacted my utility company.While the logger was connected everything was fine and hasnt occoured since. Since the main coming into my house is aluminum, I have a sneaking suspicion the power company tightened the connections at the transformer and resolved the problem at least temporarily.

Re: Blinking Lights

An appliance won't cause a 20 volt drop, if it does something else is wrong. and usually NOT the utility side on an underground service. The fact that the load is causing a drop that significant without tripping a breaker suggest (pretty clearly) a nuetral issue. If it hasnt been corrected then its still there even if you dont see it (working doesnt meen right) now theres a few issues one, when 1 leg is reading 100v the other is probably reading 140v either of those two voltages will bring havoc on appliances. second wherever that nuetral iscomprimised, its building heat under minimul load, and probably a lot of it.

You had the right idea with the light bulb, but not in the right place and not enough of a load. try it with a drill or a blow dryer and plug it into an outlet on the circuit you noticed the problem on. try to recreate it. when you find it work your way back from outlet to outlet closer to the panel when you find the outlet that doesnt create this problem on the same circuit start there re splicing and work back away from the panel on the same circuit. You will notice it, you will probably find a nuetal thats brown and dry from the heat. resplice and replace. etc etc

of course dont forget to turn the power off before you take them apart. If your not sure which outlets are on that circuit just shut every other circuit off.

Re: Blinking Lights

How is the best way to find the comprimised neutral?

There are only 2,110 circuits that have been changed/added since we have been in the house (1997).

1 line was cut in the master bedroom wall about 2 years ago when the satellite guy was drilling through the wall to pull his cable. There wasnt enough slack to make a splice so I pulled a new section of line from the outlet back to the next stud bay and made the re-connection there, a real pain to have to open the wall up. The outlet was at the end of a run.

The only other electrical work done was to pull two new lines from the main pannel into the utility for a freezer and an outlet in the garage to run a small compressor and woodworking tools.

Re: Blinking Lights

plug in something with a 5 or 6 amp load into the outlet the ups was in, measure the drop and work your way back to the panel untill you see the drop dissapear.

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