Why are the lights dimming in the kitchen when the Fridge kicks on?

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Or maybe the homeowner has exceptionally good eyesight. He may be percieving the zero cycle on the sine wave when the lights actually go out and simple correlating that with the fridge motor starting.

Just kidding ;)
 
mikehughes8 said:
Or maybe the homeowner has exceptionally good eyesight. He may be percieving the zero cycle on the sine wave when the lights actually go out and simple correlating that with the fridge motor starting.

Just kidding ;)
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I tried to count them a few times but lost count at 1
 
Here comes my 1/50th of a dollar. Troubleshooting is a process of elimination: disqualify the simplest potential problems (pardon the pun) first.

After exhausting the very obvious, such as the light being in the same circuit, loose connections (although only a shared neutral might apply, but this would cause brightening, not dimming), explore.

For instance, when faced with inrush currents causing dimming of lights, if the problem is in the service neutral, lights on the other bus will brighten.

I'd start at the panel with a voltmeter (not a wiggy this time), first line-to-line, then line-to-neutral, while starting the refrigerator (use the temp control).

The point is that any problems on one circuit shared by (or somehow interacting with) another circuit, must be at, or ahead of, where the two circuits diverge, usually the panel.
 
I would also check the connections at the panel that connect the neutral bars/busses together. I had a loose (factory installed) screw holding a neutral bar to the bus, causing flickering-thank God for my sharp-eyed helper, he saw the little arc at the loose connection.
 
My pence:

1) Understand the basic principal that you are dealing with. In a normal home wiring system, whenever current flows to a load, there is a bit of 'voltage drop', voltage lost to the resistance in the circuit feeding the load. The greater the current flow, the greater the voltage drop. The greater the resistance, the greater the drop. When a single circuit feeds several loads, then all of these loads will see the voltage drop, even if most of the current is being used by only one of the loads.

Voltage drop is _inescapable_, you will _always_ have some voltage drop in the system. In a well designed system, the voltage drop will not be significant, meaning that it will be smaller than the loads (and the customer) cares about, but it will still be there.

2) Understand what causes resistance. Simply having wire will mean some resistance. The longer the wire run to the panel, and the greater the resistance. The longer the service conductor run back to the supply transformer, the greater the resistance. But defects in the wiring can cause resistance as well. Not only are these annoying in terms of dimming or flickering lights, these are a fire hazard. A loose wire making poor contact can show significant resistance. A partial break in a wire can cause significant resistance.

3) Understand your loads and load sensitivity. A motor starting draws considerable current for a short period of time. This dynamic effect can make voltage drop problems very noticeable. A fridge might use 1.5A when running, but 10A when starting. Lights, in particular _dimmer fed_ lights, can be very sensitive to voltage drop. For this reason, it is often considered _good design_ to separate lights and receptacle circuits.

4) Understand the code issues involved. In general, lights are permitted on a circuit with receptacles, and a fridge plugged into such a circuit can be expected to cause a bit of dimming on these lights. Not a good idea, but possibly permitted. _However_, and this is important, the rules are different in kitchens. So called 'small appliance branch circuits' are required to feed most or all of the receptacles in kitchens, including receptacles for the fridge. Lights are not permitted on this circuit. If the fridge is plugged in where a normal fridge is expected, and it is on the same circuit as the lights, then this is a flaw in the wiring. The wiring may be perfectly safe, and the voltage drop no more than expected for the loading and length of wire, but this is still something you will have to fix. If, on the other hand, the fridge is out in the hallway, plugged into a hallway receptacle, then it might be entirely legal for the lights to share that circuit.

5) For diagnostics, I would first isolate the circuit that the fridge is on. Is this branch circuit shared with the lights? Should it be?

If the fridge is not on the same branch circuit as the lights, then go down the chain; at what point _is_ the circuit shared? At a subpanel? At the main panel? Look for sources of excessive resistance in these shared circuits.

Hope this helps.

-Jon
 
mgotgame said:
I am a new electrician, still in my first year @ apprenticeship school, and I have a word-order to look @ on Monday regarding a homeowner's kitchen lights getting dim whenever his Refridgerator kicks on. I don't know what to look for or even how to fix this. Any help at all would be appreciated. Thank you, Mgotgame
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You have received a lot of great advice here take this for what it is worth. When you show up on the job turn on as much as you can in the kitchen leave the guy with you there, go to the panel find the breaker for the fridge and turn it off. everything else still on? yes then you are dealing with a problem at the panel or before because that is where all the circuits are "shared". But also see if you can duplicate the problem while one of you is at the panel. look at the fridge and lighting circuits in question in the panel and snugg the wires. Remember on the way to the job discuss this with the lead guy and see if he will let you take the drivers seat in the troubleshooting process. If you find more equipment than the fridge going out on one breaker you may need to dig deeper, if you find the lights go out on that breaker (you won't) then I owe tall girl $0.05 I'll just need an address and a $0.39 stamp to sent it to her.

GOOD LUCK, and happy hunting.
 
bikeindy said:
You have received a lot of great advice here take this for what it is worth.
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There's been a lot of great advice.

One last piece of advice -- learn to dig for information. I based my response on the limited information given. If it had included the lights dimming when other things were turned on -- furnace, blow dryer, electric range, vacuum cleaner in other parts of the house -- my response would have been different. Next time, ask for more information: What else causes the dimming? What other lights dim? When did they start seeing this problem? What has changed since then?

What you learn from this service call will help you figure out future problems, and when you are older and have your own business ( ;) ) you'll have clues about load segregation, upsizing feeders, etc. that will help you avoid this problem completely.

Good luck, let us know how it works out, and get your journeypeep to sign up for the forum.
 
The human eye is very sensitive to light flicker. It may not be an electrical problem at all.
Here is a great article on the subject:
urlhttp://ecmweb.com/lighting/electric_flicker_causes_symptoms/url
past the above minus the URL into your browser

part of the article states
The brain response to the light stimulus has an inertial characteristic with a time constant of about 300 milliseconds, meaning that slow changes of luminous flux are followed (noticed) and fast changes are smoothed (unnoticed). For instance, two short changes in the luminous flux, occurring within 300 milliseconds, are perceived as a single change. Short changes of luminous flux, followed by a longer pause, are more annoying.

By the way, as a new electrician, one of my top recommendations would be to subscribe to EC&M, its free...and features articles by Mike Holt
 
LarryFine said:
Here comes my 1/50th of a dollar. Troubleshooting is a process of elimination: disqualify the simplest potential problems (pardon the pun) first.

After exhausting the very obvious, such as the light being in the same circuit, loose connections (although only a shared neutral might apply, but this would cause brightening, not dimming), explore.

For instance, when faced with inrush currents causing dimming of lights, if the problem is in the service neutral, lights on the other bus will brighten.

I'd start at the panel with a voltmeter (not a wiggy this time), first line-to-line, then line-to-neutral, while starting the refrigerator (use the temp control).

The point is that any problems on one circuit shared by (or somehow interacting with) another circuit, must be at, or ahead of, where the two circuits diverge, usually the panel.
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"Once you have eliminated the impossible, that which remains, however unlikely, must be the truth."

That's my best shot at quoting Sir Arthur Conan Doyle.

I've seen some weird stuff in residential systems. I've seen fractional horsepower grinders in attached garages cause lights on the main floor of a ranch get bright during acceleration. I've seen houses with their meters pulled out showing 10 amps on their water pipe from the street.

I'd check to see whether you've got a possible sag on one or the other line, or perhaps an ohmic connection to the utility neutral. A Fluke 78 should be sufficient, if you have the time to hang out on the SE.

My guess is congruent with the other gueses here; you have an issue with a bad neutral. The alternative is that either you or the utility has a problem with another conductor (or perhaps plural). This can be determined readily by measuring L-L, L-N and L-G during an event. Bon chance, mon ami.
 
I think this is perfectly normal and nothing is wrong. Any time a motor load starts, it will dim the lights. Don't motors draw 6-7 times the rated current for a fraction of a second?
 
The solution to the problem* is to change the lighting circuit to the other leg of the service not feeding the 'fridge.

The problem is more mental than electrical.
 
dedicated circuit

dedicated circuit

i am in agreement with m73214, and since this is a new home it probably has romex. maybe you can find a jbox that has another circuit with lighting loads that isn't fully loaded. this may prove to be time consuming, but the problem isn't unsolvable.
 
Food for Thought

Food for Thought

If the fridge is on a seperate circuit than the lighting circuit in question, move the circuit breaker for the fridge to the top of the panel giving it the least path of resistance to the main feeder. Some times if you move these demanding loads to the top of the panel closer to the main, less flicking might occur, If the fridge circuit has to travel up the main buss passing lighting circuits on its way, it may cause more nusance flickering than if it was placed upwards towards the top of the panel next to the main.
Just my 2 cents
 
RUWIREDRITE said:
Some times if you move these demanding loads to the top of the panel closer to the main, less flicking might occur, . . .
Just my 2 cents
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Good advice to always follow. I always place 2-pole breakers on one side (typically left) and single-poles on the other (as long as space permits), with the highest-rated on top and decending downward.

I never group high-current circuits side-by-side, sharing stabs; a pair of 30a's is usually my limit.

Your post also suggests an idea for further investigating (once same-circuit wiring has been eliminated): temporarily move the offending breaker to the other phase. If the light now brightens, there is a neutral-resistance issue.
 
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Bob said: "As far as the rest there are still quite a few states without licensing requirements and while I agree that is not good for our trade it does not make those that operate in those states wrong."

I disagree with you Bob, but only up to a point. I do not consider it a safe practice to send someone with less than a years experience out on a trouble shooting job by them self.

I applaud the gentleman for wanting to learn good trouble shooting practices.
 
tallgirl said:
Somehow "bare bones" and "overpriced" don't seem to go together.
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Then you've never seen the Metropolitan Condo in West Palm Beach :) $500K-$800K/unit and all the electric was code bare minimums...or less. In the hallways you'd find 4" square boxes with up to 15 #10's in them in some cases on the sconces. Someone must have gotten passed a real fat envelope on the rough inspection. We'd pull wire into the pipes and the PVC would fall apart during the pull cuz it was never glued. Smurf with 5 and 6 90 degree bends in it everywhere.

I walked off that job because we weren't allowed to fix anything.

http://www.gokenco.com/communities.asp?comm_id=1
 
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