Voltage Fluctuation

[jeff43222]

Just got back from a service call where the original symptom was flickering lights. I went to the house and observed the flickering, and it pretty much affected every light in the house. It was more pronounced when the coffee pot and crock pot were plugged in.

What surprised me, though, was that the circuits were fairly well balanced. The lights throughout the house were split among several circuits, and the kitchen receptacles were on a circuit separate from the lights. Nothing in the house drew much current. It had 100A service, and I measured 3.5A on one leg and 5.5A on the other.

Then I discovered that the voltages were not consistent. H-N on one leg at the panel varied between 110V-114V, and the other showed 126V-130V. H-G was consistently 120V on both legs. Neutral and ground were not tied together in the panel because there was an outside disconnect switch (fuses) between the panel and the meter socket. The same readings showed up inside the disco switch and on the line and load side of the meter. But these readings all go to normal if I shut off the main in the panelboard.

My thinking is that there's loose neutral somewhere upstream of the panelboard lugs or degradation of the insulation on one or more of the service-entrance wires. I'm leaning toward the loose-neutral theory since H-G is always 120V. I didn't see anything that looked problematic, though. Everything I looked at was in good shape, lugs were nice and tight, no obvious wire damage, etc.

If anyone has any other ideas, I'd be happy to hear them.

 

[al hildenbrand]

Re: Voltage Fluctuation

I think you nailed it. PoCo side failing neutral splice.

The key is the same voltage irregularity appears on the line side of the meter. If the lug connections on the line side of the meter are good, all the remaining splices back to the transformer belong to the PoCo.

Has Xcel been called?

Seems to me I've been experiencing more of these in the last year or so. . .

 

[jeff43222]

Re: Voltage Fluctuation

I just got off the phone with Xcel. They said they have entered an order in their system. Of course, it's anyone's guess as to when they might process that order.

 

[bdarnell]

Re: Voltage Fluctuation

Having worked for a utility in a cold climate, one of the things we would find is that ice would form inside of the crimps that we used at the weatherhead (we called them Insulinks) and actually force the wire out of the splice. This was especially common if the lineman didn't crimp the Insulink enough times or used one of the "one shot" dies on his press.

Just a thought.

 

[megawatt]

Re: Voltage Fluctuation

After eliminating everything on the Homeowner's side.
A method that has worked for Me is to run a temp conductor from the neutral bar, to the service neutral connection above the weatherhead.
Connect with a split bolt, & take readings again. If the voltage is still not balanced, You can tell the POCO with confidence that a bad neutral connection exists, outside the Home.
I used this last year, I was the 2nd Electrician to look at a year old flickering lights situation...POCO had even replaced the transformer to try & resolve. After bypassing all of the Homeowners connections with the temp wire, same problem existed.
I called the POCO, told them that there was a problem outside.
Tech found that Squirrels had chewed the aluminum conductors away from the service neutral...the steel core was all that was left.
Easy trouble call, & the Homeowner will think You are a Genius !!

 

[Matt Harp]

Re: Voltage Fluctuation

I have had several of these type of calls in the last few months. Most were neutral problems, one was a phase on the POCO side, and one was really odd. 120/240 single phase and 120/208 3-phase secondary both on the same utility poles. One of the 3-phase conductors had sagged and contacted one of the single phase conductors. It fried several appliances for the property owner, but didn't affect anybody on the 3-phase system. Took me 2 hours to find it and the POCO trouble man didn't believe me until he got into the bucket and saw it for himself. He said in 18 years he had never seen that happen. I should mention that here in Louisville, we seem to have a distribution system that is so quirky that even the linemen cuss about it.

 

[electricguy61]

Re: Voltage Fluctuation

I worked on a home in Lake Tahoe California with a similar problem.

The POCO had been out 3 times, redoing the connections at the weatherhead, on the pole, and even replacing the transformer on the pole. I pulled the meter, removed the meter cover, and found the neutral lug wasn't ever tightened down. Tightened the lugs, problem disappeared.

The lights in this instance flickered the most when something with a large 110v load was operating (microwave, washing machine, toaster), hence when the load on the neutral was increased.

This might be something for you to check (though be sure to call the POCO and tell them you unsealed the meter, or they could nail you for tampering)

 

[jeff43222]

Re: Voltage Fluctuation

Everything on the homeowner's side was plenty tight. The symptom was the same as you mentioned: The flickering got worse as the 120V loads were increased.

I did call the PoCo and let them know that there was a likely loose neutral splice on their end, and I did mention that I popped the meter. I pop meters from time to time, but the PoCo doesn't get all upset about it. Generally when I pop meters it's part of a service upgrade, so the PoCo gets notified after inspection.