Is it normal for lights to Dim ?


Old 01-28-06, 05:03 PM
Thread Starter
Join Date: Jan 2006
Location: Ontario, Canada
Posts: 21
Is it normal for lights to Dim ?

I recently rewired 2 plugs and 2 lights on the same circuit.

I noticed that when the vacuum cleaner was plugged in and turned on, the lights dimmed ever so slightly. But noticeable.

Is it normal for lights to dim when you plug something ( like a vacuum cleaner) in a plug that is on the same circuit. ?

Maybe this happened before with the old wiring, but never noticed.

The circuit contains 14/2 wire with a 15 amp breaker.
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Old 01-28-06, 05:12 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Every circuit on the planet will dim the lights at least "ever so slightly" when a vacuum cleaner is turned on on the same circuit. In higher-end homes, they usually keep lighting off of receptacle circuits to avoid this annoyance.
Old 01-28-06, 05:15 PM
Join Date: Mar 2005
Location: Central Florida
Posts: 149
Yes, it is normal for a vacuum cleaner to dim lights on 15A circuit. Most common vacuums draw between 10A and 12A when they're running - higher at start up. That pretty much saps the available power.

You're probably just sensitive because you did some things on the circuit...
Old 01-28-06, 05:17 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
This is normal.

Vacuum cleaners draw a significant amount of current. So do irons. When they are turned on (or cycle on, such as with an iron), the voltage drops on the circuit because of the immediate change in power. The current picks, so the voltage returns to normal.

This is why some people recommend keeping lighting on a separate circuit from receptacles.
Old 01-28-06, 07:53 PM
Thread Starter
Join Date: Jan 2006
Location: Ontario, Canada
Posts: 21
THanks for the feedback. I can now understand why lights are on their own circuit.
I thought that with the new re-wiring maybe something may not be right. Glad it is normal.

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