Strange voltage at panel/lights flickering

[patricknola]

I have a situation with a customer where her kitchen lights are flickering really bad. She has a 3 phase meter but the c phase which is a stinger leg isn't being used,she only has 2 phases going into her main panel. When all of her circuit breakers are on the voltages at the meter is 100v on the A phase and 140 on the B phase. When I trip her main breaker the voltages at the meter moves to 110v on the A phase and 128v on the B phase. The reason I was called out to her house was that her kitchen lights are flickering up and down and she say's it seems like her lights aren't as bright as they used to be. I was there when she turned on her dryer and her kitchen lights got noticeably brighter not softer. I have been to her house a few times to check the voltages on the circuits at the main panel and the sub panel and every time the voltages are never 120 and 120 on the two phases they are always moving around 100 on the A phase and 140 on the B phase.

 

[ptonsparky]

Check for a bad neutral connection. Could be at the panel, POCO transformer or any where in between. Lights dimming on one circuit and some going bright on another is a typical indicator. Could be a seriously undersized neutral, but not likely IMO. Direct buried SE Cable with a bad or faulted neutral is another.

 

[Electric-Light]

Dryer usually loads the drum motor phase to neutral. If the voltage is not symmetric between two Ls and N with the main breaker off, that's a PoCo issue.

 

[gar]

150103-1532 EST

ptonsparky has defined your problem.

Note that 100 +140 = 240, and that 110 + 128 = 238 close enough to 240 that the major problem is the neutral.

I suspect that there are multiple customers on your customer's transformer, and that is why the voltages are not 120 and 120 when the main breaker is open. Loads from other homes on the same transformer are causing the unbalance.

The neutral problem is likely at the transformer, or in the distribution wiring from the transformer that is common to your customer and the other homes on the same transformer.

This is probably all a power company problem.

.

 

[Electric-Light]

Power surge is not unique to a particular place, but American systems are particularly vulnerable because of the 3wire system we use to get 120 and 277v. The drum motor phase to neutral. If the voltage is not symmetric between two Ls and N with the main breaker off, that's a PoCo issue.

I'd leave the main breaker off until PoCo can get there and evaluate and correct the situation or she risks significant damage to electronics. 140v is right on the verge of damage. With passive devices, you'd have to run it in the order of minutes for any real damage and split second surge which will shoot up close to 240v don't affect them. One separate temporary separately derived 120v circuit can be made with 240 to 120 isolation transformer to power refrigerators/freezers and bare minimum lights (with an extension cord) to get by to prevent thaw out and have minimal lighting to avoid total darkness.

A whole house surge protector is a good idea these days. It would be like the red cables in the drawing below. Your stuff is green cables. The center post is the neutral. It's not supposed to pivot, but if it does, the red wires arrest the beam so your stuff do not rip apart.

The lights are brightening, because as you pull on one end, the center is tilting and the other end is shooting up. The two sides don't equalize even when the breaker is off, because the center post is probably shared with neighbors.

 

[ActionDave]

Bad neutral. Be careful. Call POCO.

 

[JDB3]

Went to residence where lights got brighter when AC came on. Sparks behind electric range. Loose neutral to outside service panel. Range location had piping for gas. Was picking up "neutral" through gas pipe, feeding through range.

 

[skc]

intermittent voltage spike

intermittent voltage spike

When tested pnl ( 240 v) tested fine line to line lines to neutral and to ground. Problem blew lamps at fixture and work light halogens burnt out shattered glass. No multi.. individual 130v branch. Tested fine when checked. Any ideas on what could havr caused spike?

 

[Electric-Light]

When tested pnl ( 240 v) tested fine line to line lines to neutral and to ground. Problem blew lamps at fixture and work light halogens burnt out shattered glass. No multi.. individual 130v branch. Tested fine when checked. Any ideas on what could havr caused spike?

The voltage can look fine at panel under minimal load.
Wire up two 40W bulbs in series. So you have 1--x--2 where the x is where they're joined.

Through a 15A two pole breaker(for safety reasons, do not ever tie directly to bus bars!) , connect 1 to L1, 2 to L2. connect "x" to neutral. Have all the other breakers turned off. If one bulb gets bright and the other one gets dim like this, call the PoCo. This test is best done the very first thing in the morning or the very last thing of the day so the activities by neighbors produce the symptoms.

If it doesn't, it maybe on the house side, such as loose neutral in the panel, particularly with Aluminum service wires.