Lights dim when turning on appliances


Old 04-17-06, 07:51 AM
Thread Starter
Join Date: Apr 2006
Posts: 23
Lights dim when turning on appliances

Ok, so i just rewired my garage and added a 20 amp circuit straight from the breaker panel for four outlets. Nothing else on this circuit. The garage lights I kept on the original circuit which is a 15amp and includes some of the first floor lights and outlets. When first turn on a power saw or shop vac that is plugged into the 20amp circuit the lights dim for a second. I'm confused. I figured if I put in a new circuit i wouldn't have this issue. i have 100amps on my main breaker. Also, I have a split 15/20 C/B. Should I replace it with a single 20 amp C/B? Thanks!
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Old 04-17-06, 08:00 AM
Join Date: Nov 2004
Location: CA
Posts: 2,041
Large motors such as a saw or shop vac draw a very large momentary starting current......probably well exceeding 20 amps. This is why breakers and fuses are time-lag devices. They can absorb the momentary overload, and nothing in the circuit is damaged. However, Ohm's law is always in effect, so a momentary surge can cause a momentary voltage drop at the source, hence flickering lights.

Without knowing more about your whole set-uo, we cannot say for sure something is wrong. It is likely just a normal situation.
Old 04-17-06, 08:10 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
This does not sound like anything is wrong. Replacing the breaker won't help.

Having the power company install a new transformer closer to your house will likely help, but they aren't likely to do this.
Old 04-17-06, 08:14 AM
Thread Starter
Join Date: Apr 2006
Posts: 23
thanks for the fast reply. My setup is pretty straight forward, 20 amp breaker, 12 gauge wiring to four outlets, first in series GFCI protected. I'll just chalk it up to "sucky" amperage from the Electric company (i live in a housing dev.)

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