Anthony3809
New User
- Location
- Lubbock Tx
- Occupation
- Apprentice Electrician
When I turn on my garbage disposal in the kitchen, the lights in the kitchen brighten for a half a second then go back to normal. What is causing this?
Lights Brighten
- Thread starter Anthony3809
- Start date
- Status
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Loose or intermittent neutral somewhere. Magic smoke coming soon.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Welcome to the forum. Voltage drop can occur in any current pathway, but only a drop along a shared neutral can cause the voltage between a line and the neutral to rise as the voltage from the other line to the neutral droops.
See: https://forums.mikeholt.com/threads/understanding-the-neutral-conductor.140537/#post-140537
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
OP: you don't sound like an electrician.
As others have noted, the lights getting brighter is caused by resistance in the neutral of a shared neutral circuit.
This may indicate a problem (loose connection) or it may simply be normal resistance combined with the high starting current of the disposal motor.
A professional electrician can evaluate this. If this is a new symptom, then it indicates a problem that needs to be dealt with quickly.
Jon
As others have noted, the lights getting brighter is caused by resistance in the neutral of a shared neutral circuit.
This may indicate a problem (loose connection) or it may simply be normal resistance combined with the high starting current of the disposal motor.
A professional electrician can evaluate this. If this is a new symptom, then it indicates a problem that needs to be dealt with quickly.
Jon
4x4dually
Senior Member
- Location
- Stillwater, OK
- Occupation
- Electrical Engineer/ Ex-Electrician
Well, he does say he's an "Apprentice Electrician".....so sounds like he's still learning.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Well, he does say he's an "Apprentice Electrician".....so sounds like he's still learning.
Admittedly I missed that, and this would change my answer, in that I would offer to help walk through diagnosing this, figuring an apprentice would be able to understand the limits of their current skills.
-Jon
kwired
Electron manager
- Location
- NE Nebraska
Note that bad neutral very well could be anywhere from common neutral in a multiwire circuit, a feeder neutral if you are supplied from a subpanel, to the service neutral which could be anywhere from your service panel to the POCO transformer terminals.
It could also simply be long undersized lines say in POCO distribution. That motor will draw high current briefly upon energizing it which could pull one leg down but the other lighter leg actually sees a rise in voltage due to the voltage drop on the neutral even though there is no compromised connection. Once motor has accelerated the load current is low enough again that things are pretty much "normal" to the naked eye anyway.
It could also simply be long undersized lines say in POCO distribution. That motor will draw high current briefly upon energizing it which could pull one leg down but the other lighter leg actually sees a rise in voltage due to the voltage drop on the neutral even though there is no compromised connection. Once motor has accelerated the load current is low enough again that things are pretty much "normal" to the naked eye anyway.
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