bad surges

[b_animal]

I did a panel change and now when you turn on the garbage disposal the lighting will go way dim untill the disposal gets up to speed.

or if you start a toaster some of the lights dim and some light get brighter

the voltage drops or gains like 6 volts

what is causing this ?

am I getting bad power from the power company or am I doing something wrong, all connections are tight ran new ground rods, neutral bonded at panel!

any ideas guys

 

[tom baker]

Is this a shared neutral to the kitchen perhaps a MWBC?

 

[George Stolz]

Open neutral somewhere.

 

[dbuckley]

some of the lights dim and some light get brighter

Some lights getting brighter is an absolute giveaway of an inadequate neutral connectivity somewhere down the line.

Be leery that your troubleshooting doesn't convert an inadequate neutral to an altogether missing neutral, with the subsequent and total munting of your customers stuff. Even if you dont break it, if it breaks while the electrician is on site, the customer will assume that the electrician is responsible for the carnage.

 

[gar]

1000427-1911 EST

At the main panel on the actual input wires, not the lugs, make your voltage measurements. If you see the same disparity in voltages under the same conditions, then the problem is between the main panel and the power company transformer and is at least a problem in the neutral.

If the voltages are good on the input wires, then check the voltages on the main panel bus bars. If these voltages are good, then go to the next step.

Are there any sub-panels? If yes, then repeat the experiment at the sub-panel(s).

Still have a problem, then turn off the circuits with the problem. From a breaker in the main panel that does not have the problem attach a temporary outlet. To this connect a long extension cord. Make up a way to use the hot wire from the extension cord to connect to the hot side of a 1500 W heater. This you do not connect until other connections are made. Make a single wire from a plug neutral to the neutral side of the heater and a connection for a meter probe. Bring out a wire from the extension cord neutral to a connector for the meter probe.

The plug with the neutral wire is plugged into the circuit to be tested.

The meter is thus connected between the neutral being tested with a load, and the neutral in the extension cord which is carrying no current and therefore is simply an extension of the meter lead back to the neutral at the main panel. Thus, the meter will measure the voltage drop on the neutral being tested from the main panel to the point of test. Plug the hot side of the heater into the extension cord hot. This provides up to about 12 A current thru the suspect neutral. If this portion of the neutral is good, then the voltage drop probably is less than 2 V. 1000 ft of #12 is about 1.5 ohms. Most houses will have main panel to outlet runs under 100 ft. 12 A at 0.15 ohms is 1.8 V .

Be careful because you may be dealing with some electrically hot wires.

Note: by turning off the breakers to the problem circuits any voltage developed on the neutral under test should not damage loads on those circuits.

You should draw a schematic of what I have described and understand the logic before doing any tests.

.