Electrical box grounding or supply issue?

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papakevin

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I’ve replaced an old screw in fuse panel with a new 100 amp panel and breakers. When using a corded circular saw plugged into one of the new circuits (14g wire), all the lights in the house (on separate circuits) would dim. Is this caused by a bad ground, bad feeder wire from meter to box, too small of a feeder wire gauge or something else? How could I fix? Thanks.
 

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ajaynejr

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Most likely a loose connection in the new panel or upstream.

When lights throughout the house get dim, are there a few that don't dim? Put an incandescent (old fashioned bulb) light on a circuit that does not dim for a second opinion.

Better yet, get a voltmeter (or multimeter) so you can measure exactly how many volts' drop you are experiencing. A drop of 2 volts can be ignored but a drop of fifteen volts is a bad situation. If incandescent lights dim very noticeably that is a bad situation.

This needs attention quickly. Allowing a loose connection to persist can result in damaging the panel or meter box or other location where the loose connection is. Turn off as many things as you can to reduce the total load until you can find and fix the problem.

Stand with both feet on dry cardboard, put one hand in your pocket, and carefully press your other thumb on non-metal parts including in the breaker panel. Unusual heat might be the location of a bad connection.

Not a too small feeder because if the feeder can't handle one hair dryer or one circular saw then the feeder won't handle the rest of the things in your house used several at a time. (Normally a feeder will not allow you to run absolutely everything all at the same time.)

Not a bad ground. If improving the ground improves the performance of electrical things that means something else, probably the neutral, is also bad. The neutral is part of the normal path, or circuit, for the electrical current. The ground is not intended to carry current but sometimes it does carry some.

Probably not a bad feeder wire. It is rare for a wire to break in the middle of a run so as to leave two hidden broken ends that make poor contact or to leave a thin section (of a few remaining good strands) in the middle.
 
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Eddie_T

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I don't see a neutral coming into the box from the meter. If there is no neutral the ground is the return for any unbalance of 120V circuits, I do see a small wire going into a center lug.
 

ajaynejr

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Correction, you are right. When there is only one more wire (besides the hot wires) coming into the panel from the meter, that one wire serves as both neutral and ground. Or metal conduit can be the ground.

The third fat wire must go to the neutral lug in the panel or neutral bus bar. There are a variety of ways to ground the panel frame/back, one way being a (usually) green screw in the neutral bus bar digging into the panel back.

To meet today's code the shared neutral and ground may go only as far from the meter as the first whole house disconnecting switch or breaker, which may or may not be in the panel you just installed. Thereafter separate neutral and ground are required. It will still work and lights won't dim a lot with with good wires and adequately tightened connections.

Some older homes may be grandfathered with the shared ground and neutral going past the first whole house disconnect. But don't be surprised if your inspector calls out an irregularity; a new panel might stop any grandfathering of nearby wiring you might have or need.
 
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afjes_2016

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I can't see much of anything in detail. It won't zoom in enough for my old eyes.

I do see what looks like a neutral coming in.

What's with all the sheathing inside the panel? You really only want to have about 1/4-1/2" of sheathing coming into the panel.

I would think you did not replace the conductors from the meter to the panel - does not look like it. Not that you had to though.

The most important things are that your connections are tight and secure. Did you use Noalox on the aluminum conductors going into the main lugs of the panel?

Also the ends of the conductors going into the main lugs did you strip the insulation off completely around the entire conductor? I have seen some that were stripped by a utility knife but not stipped cleanly all the way around the conductor circumference. This then does not create a complete connection to the exposed strands of wires in the conductor. Make sure your main lines are free of any insulation. Make sure they are nice and tight in the lugs and make sure you neutral is tight.

Also something important. Usually the old fuse panels that were main panels were fed with 60amp service. This would mean that normally the service conductors are only rated for 60amps. What was your service before you installed the new panel? If your service entrances cables were only 60amps you can't just put in a 100amp panel unless you run the main conductors into a disconnect rated at 60amps and then into the 100amp panel. You main disconnect can't be rated higher than the rating on your service entrances conductors.
 

Eddie_T

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Using clip leads to the naked bus stabs measure the 240V when turning the saw on. If the 240V doesn't change the feeders and connections are good.

Move one clip lead to the neutral bar and run the test again for one bus then the other. If either shows a significant drop from 120V there is a neutral problem.
 
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