# Hair dryer causing dimming of lights in multiple rooms



## xuandu (Feb 4, 2018)

some funny stuff happening with my above-garage apartment and trying to figure out what's going on. note that i've had a certified electrician come out and have a look and he was not able to conclude anything specific, but did confirm that he doesn't see any loose wires anywhere and breaker box/circuit all look fine.

*disclaimer: i'm just a home owner learning things as i go/talk to others, not tons of electrical knowledge at all... more logic/reasoning trying to deduce the problem*

*the issue*: whenever the hairdryer is turned on (in bathroom gfci outlet), there is very noticeable dimming of LED canned lights as well as normal light above bathroom mirror. some funny things...


lights dim more based on hair blow dryer setting (cold air -> low heat -> high heat cause increased dimming as well as low power -> high power)
hair blow dryer used is 1875 watts (i also tested another blow dryer which is also 1875 watts to isolate the issue, same results regardless of which blow dryer)
all lights tested are fairly new LED recessed canned lights
when tested in bathroom, bathroom and living room lights dim very noticeably while bedroom dims slightly and don't know what kitchen lights were doing (same for when testing in living room)
when tested in bedroom, bedroom lights dim very noticeably while bathroom/living room lights only dim slightly and i don't know what kitchen lights were doing
when tested in kitchen, oddly the kitchen and bathroom lights were dimming very noticeably but not living room/bedroom
when tested on fridge plug in kitchen (different from rest of kitchen), the living room lights dimmed very noticeably but only slightly in all other rooms

i've read other older threads on this/other forums and would like to likely eliminate loose wires (electrician checked already). i've read some people mention possible loose neutral which i'm not fully sure what that is, but since there is some light dimming (even though it's different rooms depending on plug) on every plug in the house i tested on (at least 10), then it sounded like this wouldn't be the issue. 

not sure if hired electrician is fully knowledgeable so would love to get other ideas if anyone has them for either myself to try or another/same hired electrician to try. thanks in advance!


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## jmon (Nov 5, 2012)

Hair blowers do stress out the circuit no doubt. Not really a problem unless you keep tripping breakers or blowing fuses. That can create an overheating issue and possible fire hazard.

You didn't mentioned how old the house is. If it's an older house, they probably wired outlets and lights together on one breaker. Causing ur issue. 

We all know this is wrong today. All newer or rewired houses wire outlets and lights separately on there own circuit.

I would get a qualified electrician to evaluate your wiring for current standards. Just a suggestion.


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## xuandu (Feb 4, 2018)

@jmon, thanks for your feedback. house is old... built in 1932 but whole garage apartment was rewired not long before we purchased the house just over a year ago (since much of the wood of the garage apartment had rotted so they had to repair much of that, so decided to rewire and replumb that whole detached building). i would think since it was rewired within the past few years that it should be updated to more recent standards, but can't say for certain. 

breakers don't trip and fuses not blown, so that's good but the issue is that the same blow dryer that works fine in the main house (high heat, high power) is considerably slower (lights dim and blow dryer seems like it's running with less energy than even the low power setting even though it's set on high), so that's the concern. 

i just ordered a voltmeter to do some more testing to watch what happens on different outlets in the garage apartment with blow dryer on and then the same for in the main house to see what's different so i can tell the next electrician other things i've done to troubleshoot.

thanks!


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## Guap0_ (Dec 2, 2017)

Do the lights only dim when the hair dryer is used on that outlet? What else is on that circuit?


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## dmxtothemax (Oct 26, 2010)

This is a classic sign of a current limit !
Two things cause this 
1 - A local electrical grid struggling to supply demand.
2 - Wiring system faulty or just too small to carry the current
that you are asking it for !
Check that all splices are in good condition.
Check that all cables are of adequate size.

Being an old house it could be a combination of old wiring,
And just too much trying to be put thru inadequate size conductors.

:vs_cool:


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## tstex (Nov 14, 2014)

quote by OP:

"i would think since it was rewired within the past few years that it should be updated to more recent standards, but can't say for certain."

You cannot assume anything. other than not assume.

Go to the main panel and see if there looks like any new breakers were installed after the "re-wiring", and determine if those new breakers are in addition to what was there before the install? You're trying to see if new circuits were added other than just new wiring and the same breakers or new breakers? New wiring doesn't mean additional new homeruns in addition to what was already there and that was upgraded too. 

Are there any recent work-orders from an electrician that states what they did and a SOW ?

Bottom-line, no matter what you have on a circuit and anything else that draws some amps [hair dryer, microwave, power tool, etc], if lights dim, the circuit is inadequate to handle the additional load. You are exceeding the 80% recommended limit and if you plugged in 2 hair dryers, you'd probably trip the circuit/breaker. 

As stated, kitchens and bathroom are all GFCI's. If there isn't one, good chance it would be tripping.

this is something worth checking out bc you don't want to start a fire...good luck, tstex.


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## user_12345a (Nov 23, 2014)

Do the lights dim only on the circuit with the large load or all the circuits.

It's normal for a 15 amp circuit to have a bit of a voltage drop when the current exceeds 12 amps. 

If you have further concerns, can monitor voltage with a meter and see if the drop is acceptable. 

Large loads that put a 15 amp circuit either need to be used temporarily or be hard wired with dedicated circuit; hair dryer is okay. Same for a space heater for emergency heat.


If you look at any recent window a/c or dehumidifier, says right on the case to only use with dedicated circuit.


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## joecaption (Nov 30, 2011)

Bathrooms should have been wired on there own circuit not shared with any other room with 12-2 wire, GFI protected.
Pull the outlet out of the wall and see if you can see the sheathing on the cable,
12-2 on newer wiring will be yellow, 14-2 will be white.


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## CodeMatters (Aug 16, 2017)

Doewsn't sound unusual or surprising to me. 
BTW, where's the panel? In the aptmnt above the garage or somewhere else?
If elsewhere, how far away?


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## Brian John (Jul 21, 2017)

jmon said:


> Hair blowers do stress out the circuit no doubt. Not really a problem unless you keep tripping breakers or blowing fuses. That can create an overheating issue and possible fire hazard.
> 
> You didn't mentioned how old the house is. If it's an older house, they probably wired outlets and lights together on one breaker. Causing ur issue.
> 
> ...


No, it is not, it is a good way to wire a house but not an NEC requirement and tract homes would never utilize this method due to the extra copper required.


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## Brian John (Jul 21, 2017)

Dimming of lights can be caused by as little as 3 volts dip and from my experience, it seems women notice this more.

Install a new circuit to the bathroom.


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## user_12345a (Nov 23, 2014)

should be okay as long as voltage doesn't drop much below 105v.

I wouldn't worry about it, especially for a appliance that's used for short periods of time attended.

Can be very expensive to add circuits after the fact and often means drywall/plaster demolition. 

For an older apartment you have leeway, the wiring only needs to comply codes at the time of construction. Any alterations or additions of course have to comply with new codes.


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