lights dimming

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dimming lights

dimming lights

Knuckle Dragger said:
All great advice you have recived.
9 times out of 10 when there is fluctuating throughout a residential home it is a neutral or hot leg issue.
I would insist on the local POCO check the power out in the street and at the meter if you are not allowed to touch it.
Click to expand...
WOW!!! These lights have been dimming for over a month!!!
 
Knuckle Dragger said:
All great advice you have recived.
9 times out of 10 when there is fluctuating throughout a residential home it is a neutral or hot leg issue.
I would insist on the local POCO check the power out in the street and at the meter if you are not allowed to touch it.
Click to expand...
Or it coincides with a load change possibly not even a load inside the home.
 
160904-1444 EDT

There is far too much conjecture here and too little measured quantitative data.

I just ran a comparative experiment with a 100 W incandescent and the CREE LED I previously mentioned.

The voltage was adjusted by a Variac (actually a Powerstat) the light intensity was measured with a 66 year old GE light meter (probably a selenium photocell).

The results in volts and footcandles are:
Also shown are % change in intensity.

(foot candles)
CREE LED
120, 40 --- 100, 39+ ---- 80, 38.5

100 W incandescent
120, 55 --- 100, 48 ----- 80, 40


(% change)
CREE LED
120, 0% ---- 100, 0.5% --- 80, 3.7%

100 W incandescent
120, 0% ---- 100, 12% ---- 80, 27%


A casual observer watching the LED or incandescent will unlikely see the change in LED intensity from 120 to 100 V. But, will certainly see the incandescent change.

In a very tightly controlled experiment it probably can be shown that the observer can detect the change in the LED intensity even though the observer does not realize they have detected the change.

If the same observer looks separately at the light from the bulbs at 120 V excitation, and does not have them for side by side comparison, goes outdoors, comes back inside, rests for a while, has no other lights for comparison, the lights are now excited at 100 V, then with almost total certainty that observer will not detect a change in the LED light output, and may or may not detect the change in the incandescent intensity.

In JDB3's situation did changing to LEDs simply mask the problem, and there is still a voltage change at the bulb, or did the change in power load eliminate the original cause of the dimming? We won't know without investigation of the light kit or input wiring.

.
 
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As I had mentioned somewhere, I had one of the persons living there, turn down the thermostat for the AC system. I did not notice any dimming caused by this nor did I see any voltage change .
 
Knuckle Dragger's Avatar
Knuckle Dragger


Quote Originally Posted by kwired View Post
Or it coincides with a load change possibly not even a load inside the home.
Another good angle to try.

Since this residence is feed with it's separate pad mount transformer, I have no way to see if other loads are affecting this house. :happyno:
 
160904-2346 EDT

JDEB3:

Your test of turning on the air conditioner and seeing no voltage change when the compressor started is a good indication that the power company transformer, wires, and connections, for the two hot lines, are probably good. Also implies a low source impedance.

This may not imply a good neutral. However, the neutral can be evaluatee by the test I described above.

I don't really believe that you saw no voltage change if your meter resolves 0.1 V. Under steady state conditions of the compressor running I would expect at least a few twnths of a volt change.

I don't have a large air conditioner, but my neighbor has one, and I experience a momentary dimming of my 300 W tourchiere lamp from what I believe is startup of his compressor. I put my Fluke 27 on MIN/MAX and monitored voltage for several hours tonight. The most difference was about 0.9 V, but we have a cool night. My light flicker is more than a 0.9 V change. The Fluke 100 mS response time should be an adequate match to motor startup.

I will try a couple other experiments with the Fluje 27 tommtrow.

If all lights in the home are somewhat uniformly distributed between the two phases, all lights in the home simultaneously dim, and there is no correlation between dimming and some 240 V load in the home, then the cause is likely a power company primary side voltage drop. This would be seen as a change (drop) in the 240 at the main panel.

If some lights dim and others brighten at the same time, then there is a possible neutral problem somewhere.

If some lights dim on one phase while simutaneously others others on the opposite phase don't change, then you need to look somewherre on the phase with the dimming lights.

If some lights on one phase dim while others on the same phase don't dim, then you have to look somewhere within that phase for the problem. This case is clearly unrelated to the power company.

.
 
Since this residence is feed with it's separate pad mount transformer, I have no way to see if other loads are affecting this house. :happyno:[/QUOTE]

Check that suggestion off the list.:)
 
I agree that most of the time this is due to a loose neutral somewhere in the system and the problem is contingent on load and load balancing. I experienced a similar situation in a municipal building and couldn't find any obvious problems. Utility had been out twice to check. Then I noticed the neutral connection on the overhead line was wrapped together with no connector and overtime the wind blew the problem occurred. We called the utility company. They came out and said they found nothing wrong. But when I next looked they had added a connector and, of course, the problem disappeared. My advice is to have then check it and be there too confirm it was looked over carefully at the transformer and meter.
 
160905-0907 EDT

Knuckle Dragger:

Your suggestion is not totally invalid. There can be a customer on the primary side of the pad transformer that affects JDEB3's customer with some large voltage variations, but not likely for 10% or more variation.

If you look at my photos P-22 thru P-25 at http://beta-a2.com/EE-photos.html you see about a 1 V modulation of my source voltage that is uncorrelated with my power loading. This variation came from the primary side of my pole transformer. It is quite unlikely that anyone on my substation was the source of this modulation. Everything on the substation is residential. Also this variation tended to be at non-normal work hours.

To look for primary side problems look at the 240 V signal and correlate the variations with total power loading on the secondary side.

.
 
JDB3 said:
Knuckle Dragger's Avatar
Knuckle Dragger


Quote Originally Posted by kwired View Post
Or it coincides with a load change possibly not even a load inside the home.
Another good angle to try.

Since this residence is feed with it's separate pad mount transformer, I have no way to see if other loads are affecting this house. :happyno:
Click to expand...
Gar has touched this, but you may have no way, but doesn't mean it is impossible. Recording equipment may be able to show patterns and you would need to know more details on what is upstream of you (get the POCO involved most likely) and you may be able to determine when that plant down the road starts up that your voltage average drops a certain amount and it rises again at the end of a shift/day/etc. You may even have shorter term variances when a big load in that plant is started or stopped.

Out in my area the rural system voltages can sometimes vary not because of one single load but because of a lot of the same type of load all across the system having similar demand cycles. It usually doesn't vary too much but you can usually measure a little less when all the irrigation systems and air conditioning is at peak demands then when there is little demand.
 
kwired said:
Gar has touched this, but you may have no way, but doesn't mean it is impossible. Recording equipment may be able to show patterns and you would need to know more details on what is upstream of you (get the POCO involved most likely) and you may be able to determine when that plant down the road starts up that your voltage average drops a certain amount and it rises again at the end of a shift/day/etc. You may even have shorter term variances when a big load in that plant is started or stopped.

Out in my area the rural system voltages can sometimes vary not because of one single load but because of a lot of the same type of load all across the system having similar demand cycles. It usually doesn't vary too much but you can usually measure a little less when all the irrigation systems and air conditioning is at peak demands then when there is little demand.
Click to expand...

This in a somewhat upscale subdivision. It varies depending on what part of the subdivision you are in. They are constantly adding sections to it. My guess is that the utility company did not anticipate the growth that has gone on there.
 
JDB3 said:
This in a somewhat upscale subdivision. It varies depending on what part of the subdivision you are in. They are constantly adding sections to it. My guess is that the utility company did not anticipate the growth that has gone on there.
Click to expand...
Now they likely need to improve their infrastructure, good luck if it is investor owned utility that puts lining investors pockets ahead of improving reliability of the system, they won't fix it until it becomes more troublesome and consumer complaints start to increase.
 
JDB3 said:
Since this residence is feed with it's separate pad mount transformer, I have no way to see if other loads are affecting this house. :happyno:
Click to expand...

I find it unlikely that a house in a subdivision has a dedicated xfmr.

Since the weather has been cool the past few days, I have not noticed any dimming lights here. It happens every summer on hot days. It's on the POCO end; we have no MWBC in the house, no bad service neutral. If you had a failing/failed neutral, and a major voltage drop on one leg, you'd have a voltage spike on the other and fried 120V electronics.

Any idea the size of the wires feeding the house and the distance from the xfmr to the meter? Ours is almost 300' from the pole mounted xfmr: 160' down the 'secondary' pole mounted lines (120V 'A' leg, neutral, 120V 'B' leg), 80' across the street and yard to where it mounts to the top of the house, down 20' the rakeboard, then 60' back across the house to the meter.
 
I find it unlikely that a house in a subdivision has a dedicated xfmr.

You may find it unlikely, but as a guy in the trade since '74, I have learned a "few" things.:roll:
This transformer is set up to feed more houses, BUT since they have not been built yet, it is just feeding this one house!
 
160906-0958 EDT

I live in a subdivision. My home plus one other, and two street lights, are supplied from one 50 kVA transformer. There will never be more homes on this transformer.

Just outside of town, but still a subdivision, there is a home with close to a 1000 A single phase service. I don't know the need. This person had my son make solid bronze floor box covers (about 10 total) at over $1000 each plus UL costs.

At my home measurements with my Fluke 27 in MIN/MAX mode are below. I don't have large loads or large load changes. My neighbor has an air conditioner. Yesterday was mild. I don't know whether the air conditioner ran. A fair part of the voltage variation is probably from the transformer primary side.

The measurements are continuous and sequential. Between the last two of the first three measurements resetting of the Fluke MIN/MAX was not done. After this MIN/MAX was reset after each measurement. The time values are for when MIN/MAX was read, and the measured values are for the time period prior to the time of recording.

If I did not miss something, then the largest MIN/MAX difference was 4.1 V.

Fluke MIN/MAX response time is listed as 100 mS.

Date & Time ----- MAX ----- MIN ----- Instantaneous value at end of time period

160905-0725 --- 124.4 --- 121.8 --- 123.3
Reset
160905-0820 --- 124.2 --- 122.2
160905-0845 --- 124.2 --- 122.2
Reset
160905-0850 ------------------------ 123.2 --- turning on kitchen light caused drop of 0.3 V (250 W)
Reset
160905-0945 --- 124.1 --- 122.7 --- 123.2 --- microwave was on within this time period
Reset
160905-1030 --- 124,0 --- 121.8
Reset
160905-1115 --- 124.1 --- 122.5 ------------- dishwasher was on during this time
Reset
160905-1225 --- 125.1 --- 122.7
Reset
160905-1520 --- 124.7 --- 122.1
Reset
160905-1705 --- 124.5 --- 121.9
Reset
160905-2300 --- 124.3 --- 121.0 --- 122.5
Reset
160906-0935 --- 125.5 --- 121.4 --- 123.8
Reset
160906-1040 --- 125.1 --- 123.1 --- 124.2

.
 
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JDB3 said:
... mobil devices ...
Click to expand...

mobil-logo.jpg
???
 
160906-1224 EDT

Just ate lunch and looked at the Fluke 27 and saw this result:

Date & Time ----- MAX ----- MIN ----- Instantaneous value at end of time period

160906-1145 --- 126.9 --- 123.2 --- 123.7 ---- present temperature 80 F.

At this outside temperature there should not have been a big load increase that would caused the substation to increase voltage. Need some power company people to tell us what typically occurs with voltage regulators.

Somewhat unrelated, but I don't believe we have a single home in our neighborhood with PV on the roof. Few homes in our city have PV, I know of one. The University has one moderate size array on North Campus. There are a scattering of PVs outside the city. At Ford World Headquarters in Dearborn, MI, there is a big array, and a moderate sized one at the Ford assembly plant in Wayne, MI.

.
 
gar said:
160906-1224 EDT

Just ate lunch and looked at the Fluke 27 and saw this result:

Date & Time ----- MAX ----- MIN ----- Instantaneous value at end of time period

160906-1145 --- 126.9 --- 123.2 --- 123.7 ---- present temperature 80 F.

At this outside temperature there should not have been a big load increase that would caused the substation to increase voltage. Need some power company people to tell us what typically occurs with voltage regulators.

Somewhat unrelated, but I don't believe we have a single home in our neighborhood with PV on the roof. Few homes in our city have PV, I know of one. The University has one moderate size array on North Campus. There are a scattering of PVs outside the city. At Ford World Headquarters in Dearborn, MI, there is a big array, and a moderate sized one at the Ford assembly plant in Wayne, MI.

.
Click to expand...

Can you plot the data? It may not have been POCO raising voltage so much as maybe it was a load going offline which caused a momentary spike. If it held at 126 I'd be more inclined to believe POCO is pushing it that high.

We run dataloggers 24/7/365 and it's a repeated pattern every day bottoming around 119 and peak around 123.
 
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