loss of power

[Joe Werle]

I'm helping out a widowed friend whose house has a newer 200 amp panel. Lack of money precludes hiring a real electrician. The lights work but when I try to run my 7.5" skilsaw the power drops and it runs slow or just grinds. The lights either dim or get brighter. I've checked for 110 volts coming in and going out of the main. Friends suggest the amperage is what I need to check. Not sure how to do that. Others suggested that the grounding is weak or loose, but it seems the new panel is grounded to an exterior ground rod as well as the neutral coming in off the pole. The friends son, who is out of state, thought there is a short which could be draining off the power, possibly connecting to the pipes and ductwork under the kitchen. I was not brave enough to verify that.
Is there a troubleshooting process/system available? It seems there are so many options I get lost trying to track the problem down.
In the new panel there are two double pole breakers and 5 new 110 breakers. One of the double pole breakers goes to the old panel which also has a 100 amp main. ( from there it ties into the existing Romex and BX circuits. I turned off the secondary main ( Called a 'slave'), and rewired a single 110 receptacle into one side of the other double pole breaker ( a 50 amp to the stove) Tried my saw in that temporary circuit and still have the same loss of power.
After I got home last night I thought about turning off all the breakers and all the other grounds- except for the temporary one I'm using. Would that isolate the problem?

[Thatguy]

It's a high resistance [bad] neutral.

If the saw is running on 100v the other side of the neutral is getting 240-100 = 140v and there is 20v across a connection that is supposed to have only a few mV across it.

With some appliances turned on [toasters and the like] put your voltmeter across the bolted neutral in the panel to see if that's where the problem is. If you short anything there is an arc-flash danger. Don't turn on incand. bulbs or expensive electronic stuff.
The bad connection may be hot and may make frying noises.

If the problem is upstream of this bolted connection you need to involve PoCo.

[Billy_Bob]

Main electrical wires to an electrical panel are "different" from other wires.

These many times are aluminum and also carry a very high amperage.

When aluminum wiring is installed, anti-oxidant paste needs to be applied to the bare wires before they are tightened down under the main lug nuts of an electric panel. This keeps the aluminum wire from "oxidizing". If it oxidizes at the connection, the connection will become bad, and there will be little or no electricity which can "flow" through.

So sometimes the person installing a main panel does not apply this paste, then later the main electrical connections fail.

Also wires carrying high amperage need to be torqued down to a certain tightness, which is specified on the panel label or in the installation instructions. "Tight" is not good enough for high amperage connections...

If not tight enough, the connection will not be good enough to carry the high amperage. The connection will then heat up! Then at night when all the electrical things are turned off, the connection cools down. Next day heats up again. This repeated heating/cooling of the connection can cause the connection to become loose and then eventually fail.

So sometimes the person installing a main panel or meter base does not torque down the main wire lug nuts as specified on the label. Then the main connections can fail.

The main connections which can fail are in the meter, in the main panel, and from a main panel to a sub panel. Also the connections with the electric company wires at the house or at the electric pole.

Some electric companies will come out and "retorque your lug nuts" for you. In other areas they will disconnect power for you, then you or an electrician can then safely retorque the lug nuts.

Note that there is power present AT ALL TIMES in a main electric panel even with the main breaker off! So don't touch a thing unless the electric company first disconnects power.

Torque wrenches and hex sockets are not cheap. Might be about the same cost to call an electrician if necessary?

Then there is the young man "King Kong" syndrome! I work with a guy who has King Kong muscles and tightens everything too tight... To the point things strip out and break. If I let him loose on an electric panel with a long torque wrench, the bolts would be stripped out and the panel torqued off the wall by the time he was done! So for these guys, a torque wrench and the specifications on the panel are needed so they don't go overboard...

[220/221]

Did you try plugging into different citcuits? The kitchen and washing machine are your best bet (20 amp dedicated circuits)

If you get the same results on all circuits, call the power company. If this is only happening on one or two circuits you will not be able to troubleshoot it.


Call power company first. tell them you suspect a problem with the neutral and ask them to do a load test. It's (generally) free.