lights dimming

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JDB3

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San Antonio, Texas
Have a single family dwelling, under 2400 square feet, total electric, hot tub, future pool, with a 320 amp service. Family moved in March/April of this year. They said that lights started dimming a month ago. No other problems.
Off the 320 amp meter base, it feeds 2 200 amp Main breaker Homeline panels. One of which is for 15KW heat, hot-tub/future pool panel, and 5 tom a/c unit.
Second panel feeds cook-top, oven, & rest of house.
With light meter, did not detect any dimming in bathroom (said they really dimmed today).
In a secondary bedroom, light kit on fan came on (around 17 foot candles) and within seconds dimmed (around 12 foot candles). Voltage stayed constant, connections @ switch & junction box @ fan/light good.
Connections at breakers & neutrals, lugs in panels (snug).
Utility company said their end was OK.
Master bath lights on B phase, bedroom on A phase.

Any Thoughts? :?
 
Did you test your phase connections at the load side of the meter and into the main panel. If it is just the two rooms then perhaps a loose connection on that circuit.

Does the dimmng only happen when a/c comes on?
 
Dennis Alwon said:
Did you test your phase connections at the load side of the meter and into the main panel. If it is just the two rooms then perhaps a loose connection on that circuit.

Does the dimmng only happen when a/c comes on?
Click to expand...

I checked the connections coming into my 2 200 amp Homeline panels. Utility company frowns on cutting their seal. Connections & voltage was fine.

There was no dimming connected with AC coming on. These are 2 different circuits & each on a different phase.
 
If it is not happening anywhere else in the house then you need to go thru the circuits that are the issue box by box. Check the neutral bar connections
 
Dennis Alwon said:
If it is not happening anywhere else in the house then you need to go thru the circuits that are the issue box by box. Check the neutral bar connections
Click to expand...

They claim that it is happing through out the house & all the time ?? Of course when I was there, I just saw it in the one bedroom. They did not say anything about any effect on their electronics. (The man use-to work for a rather large electronic supply company in this area.)
 
Whilst these types of problems can be caused by a multitude of problems in your electrical system,
It can also be caused by problems in the local POCO grid,
if it is running out of puff, then dimming is the result.
You need to establish some type of pattern to it.
does it only happen at certain times of the day.
During certain types of weather maybe
Only on one MWBC
Only on one particular circuit
Only on one particular hot feed

If you cannot figure it out
get an electrician in to check your main panel and feed lines
this is not something a DIY should mess with !
 
Last edited:
dmxtothemax said:
Whilst these types of problems can be caused by a multitude of problems in your electrical system,
It can also be caused by problems in the local POCO grid,
if it is running out of puff, then dimming is the result.
You need to establish some type of pattern to it.
does it only happen at certain times of the day.
During certain types of weather maybe
Only on one particular circuit
Only on one particular hot feed

If you cannot figure it out
get an electrician in to check your main panel and feed lines
this is not something a DIY should mess with !
Click to expand...
:? His profile says he's a contractor.
 
JDB3 said:
. Lights dimmed a few seconds after turning them on.
Click to expand...

Just something off the wall that I have noticed in the past is if they have those hybrid GE bulbs (the ones that have a halogen filament that comes on at first along with fluorescent tube and once fluorescent warms up the halogen shuts off) tend to give you results like this.

Otherwise I would contest that the POCO may need to upsize transformer, espessially if it serves many homes. Their estimation of load may be a little weak if they were not informed of A/C size durring construction. Some of these 5 ton units have a substantial locked rotor current. My parents unit is damn near 196 locked rotor amps and dimmed the lights to practically nil. I had poco up size transformer which did help.
 
The dimming on the light kit is next to the receptacle...
Click to expand...

Really guys. Please proof read and correct your posts because it drives me nuts trying to figure out what you are saying. This is getting worse and worse with mobil devices.

I stuck a digital volt meter into the receptacle that the feeds the switch that goes to the light kit/fan. There was no fluctuation at all with switch off or on. Lights dimmed a few seconds after turning them on.
Click to expand...

So you are saying that the lights dimmed with no change in voltage?

-Hal
 
Have you monitored voltage at the fixture which is dimming while it is dimming?
You'll have to drop the fixture to do this.
 
JDB3 said:
Have a single family dwelling, under 2400 square feet, total electric, hot tub, future pool, with a 320 amp service. Family moved in March/April of this year. They said that lights started dimming a month ago. No other problems.
Off the 320 amp meter base, it feeds 2 200 amp Main breaker Homeline panels. One of which is for 15KW heat, hot-tub/future pool panel, and 5 tom a/c unit.
Second panel feeds cook-top, oven, & rest of house.
With light meter, did not detect any dimming in bathroom (said they really dimmed today).
In a secondary bedroom, light kit on fan came on (around 17 foot candles) and within seconds dimmed (around 12 foot candles). Voltage stayed constant, connections @ switch & junction box @ fan/light good.
Connections at breakers & neutrals, lugs in panels (snug).
Utility company said their end was OK.
Master bath lights on B phase, bedroom on A phase.

Any Thoughts? :?
Click to expand...

Observations and theory:

Same happens here about this time every year. It gets hot, everyone has their ACs running full bore (especially after everyone gets off of work and peak temps happen from 3-6pm), xfmr is overloaded a bit, and the next thing you know, lights dim noticeably (perhaps 15%) and if you have a bathroom exhaust fan on, you can hear it slow down and the pitch lowers. **

I fail to see how the secondary bedroom lighting voltage remained the same while the light levels dipped noticeably (17 to 12 foot candles).. perhaps the voltage was higher on startup and you didnt catch it? .

PoCo saying everything is fine on their end... they are probably correct in this case. Transient minor overloads of an xfmr are to be expected in severe weather. Voltage dips/sags will happen. I havent timed ours with a stopwatch but istm the typical one lasts 5-15 seconds, which is probably about the amount of time a very hot AC compressor that is restarting will draw the most current.

*eta: Dominion Power offers rebates by installing load shedding/curtailment devices on central heat/air. On days where it isnt *quite* hot enough for them to kill your AC for a 2 hour block, the lights/fan dimming is most noticeable. IOW, it's more likely to be seen on a 93* day vs a 99* day.
 
JDB3 said:
In a secondary bedroom, light kit on fan came on (around 17 foot candles) and within seconds dimmed (around 12 foot candles). Voltage stayed constant, connections @ switch & junction box @ fan/light good.
Click to expand...

JDB3 said:
The dimming on the light kit is next to the receptacle that the home run goes to. From that receptacle the run goes to a closet light that does not dim.
Click to expand...


If the voltage ( feeding fixture ) is good and the fan lights dimm then I would suspect a bad switch in the fan light kit. Can you check the voltage in one of the light sockets?
 
One more thing,
If your voltage reading of the circuit stays steady when the bulb dims it could be that the socket has arcing going on between the shell and that little aluminum rivet that attaches it to the fixture wire....see it all the time. It gets stretched every time a bulb is replaced and/or degraded with heat.
Ive noticed some changes in the past couple years in some socket designs which seem to address this issue.
 
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