Light dim when using power tools

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papakevin

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I’m remodeling an older house which originally had a 60 amp main with screw in fuses. I’ve upgraded the electric panel to 100 amp service and had a certified electrician replace the main supply line from the meter to the panel and install a new ground. I’ve installed a new plug and new wire to a breaker and have been using it for a circular saw. When I kick it on, the lights in the house dim initially. I would have thought replacing the panel would have eliminated that issue, so looking for suggestions for why this is happening. The lights in the house are using the original wiring from the 40’s. Thanks.
 

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oldognewtrick

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Does this happen to all circuits or just the one on the line with the saw?
 

joecaption

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It was very common long ago to have lighting and outlets on the same circuit.
It's also very likely the wiring is undersized.
It's best to be running that saw off of a 20 amp. circuit with 12-2 wiring.
 

Eddie_T

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Since you say the saw is on a separate breaker I see no way the rest of the house wiring could be involved. If the dimming is momentary it's probably OK. I haven't seen any papers on it but I suspect current inrush to the transformer and the inductive load of the saw create a short lived phase shift between current and voltage.
 

papakevin

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Thanks. Yes, I added an outlet to the new panel with 12/2 wire and it goes from the breaker directly to the outlet which is below the box, so it is on a dedicated circuit. I’m just surprised the house lights will still dim after installing a new ground to the new box and new feed line from the meter to the panel.
 

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