I'll return with the results after I get it installed.
Blinking Lights
- Thread starter markstg
- Start date
- Status
I'll return with the results after I get it installed.
Iron_Ben
Senior Member
- Location
- Lancaster, PA
In my view, post #60 was getting pretty close to the mark. Reducing the impedance in your service, even if only by 30%, would make a noticeable difference. You say that the POCO is "not interested" in your blinking lights. I'm a retired engineer who worked for a POCO for 23 years and we were always interested in blinking lights like this. Yes, we bitched about it, but when a customer called in with this complaint (and I got a few every year), we went to the home, observed and sometimes measured the flicker, and then did what it took to make the upset customer happy. Sometimes it meant spending money to shorten the service, which at times included extending the high voltage. Or changing #2 or # 4 to 4/0 perhaps. And so on and so forth. I would call them and get an engineer or tech sent to the house so they can observe the flicker when standing next to you. They might be a lot more willing to spend a few bucks to placate a good customer than you think.
Kwired,
I found a paper that puts numbers and voltage/current vrs time traces to exactly what you are saying. Its a pdf and it is to large to post here. I'd like to share if I knew how.
kwired
Electron manager
- Location
- NE Nebraska
Post a link to the page where you found it.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I have been working with the area engineer but she so far says all her data indicates all is well from the Utilites prospective. Her calcs using monthly useage data shows 50% transformer loading therefore there is no way they will change the transformer. I told her all is well from a steady state condition, it is my compressor start transient that is the issue.
I wonder if the 80 ft. of underground service conductors are changed to copper and/or upped a size would make a difference?
They could relocate the pole mounted transformer over 1 pole so that the lateral distance is shortened to 0 for my service drop. I'll try again with the Power Company. (Wish I would have told them I needed a 400A service.)
Iron_Ben
Senior Member
- Location
- Lancaster, PA
Well, you're 100% right and she is wrong in this case. Steady state transformer loading is not the issue and she should know better, unless maybe she's only six months out of school or something.
At my old job we didn't have copper triplex, only aluminum. But we've pulled out small wire and pulled the biggest we could into the existing pipe, to good effect. If that 80 foot of underground is 2", 4/0 triplex would pull in easily. The biggest we used was 350 mcm, and that would be tough, but if really greased up it might go.
Relocating the transformer is a good thought (although that increases flicker for other customers; maybe you can get a dedicated transformer on that pole) and that plus upsizing the underground to the biggest that would fit in your pipe would do the trick I bet.
I say give her a chance to do the right thing but if she balks ask to speak to her supervisor. This could be a good learning experience for her. I hate to think she holds a BSEE degree; flicker is a fundamental concept for a power company engineer.
Ben
At my old job we didn't have copper triplex, only aluminum. But we've pulled out small wire and pulled the biggest we could into the existing pipe, to good effect. If that 80 foot of underground is 2", 4/0 triplex would pull in easily. The biggest we used was 350 mcm, and that would be tough, but if really greased up it might go.
Relocating the transformer is a good thought (although that increases flicker for other customers; maybe you can get a dedicated transformer on that pole) and that plus upsizing the underground to the biggest that would fit in your pipe would do the trick I bet.
I say give her a chance to do the right thing but if she balks ask to speak to her supervisor. This could be a good learning experience for her. I hate to think she holds a BSEE degree; flicker is a fundamental concept for a power company engineer.
Ben
kwired
Electron manager
- Location
- NE Nebraska
I'd bet big $$ that if you measured voltage at transformer terminals it doesn't fluctuate nearly as much. POCO's have pushed transformers harder then we will ever push one we install under NEC rules, for a very long time. Voltage drop is a huge deal for 120 and 240 volt circuits, especially when running something 80 feet or more. Problem with many homes is the starting current of an AC compressor is one of the most common problems with voltage drop. There is seldom any other motor load that draws such a starting surge of current and that is why it seldom is noticed with anything else. I bet your clamp on meter doesn't register fast enough to display the actual peak current drawn at startup either, it is likely much higher for a few milliseconds.
Even a peak reading clamp on ammeter?
kwired
Electron manager
- Location
- NE Nebraska
I will not claim to be expert on meters, but will say one possibly needs to look at the specifications of the meter used to really have much of an idea. I will also say the less the meter cost, the less likely it can take such short term readings with any accuracy.
The web page below shows fluke meters for in-rush current function (on most models) for measuring starting current for motors,
lighting, etc.
http://www.weschler.com/_mergefiles/299300301302303.pdf
lighting, etc.
http://www.weschler.com/_mergefiles/299300301302303.pdf
kwired
Electron manager
- Location
- NE Nebraska
Now if we only knew if markstg was using one of those. But still depends on the meter specs. looks like the ones mentioned there will register a value that lasts for at least 100mS. Which when making precision electrical measurements is an eternity.
I have the amprobe acd-4 and i'm sure it is not capturing the starting inrush current.
The service cable size is #4 aluminum and I have 2-1/2" conduit. Speaking with the POCO engineer they still are not willing to entertain changing the service cable.
The Power Quality meter used by the POCO to monitor my service was a Power Monitors Inc Guardian. She sent the file to PMI and below is what the PMI tech responeded with:
The flicker report shows little flicker on CH1 and 2, There is a lot of chatter on 3 and 4 which is normal.
When his amperage on CH1 goes up to say 132amps, his CH2 amperage goes up 1 amp. Whats strange is both CH 1 and 2
voltages go down by 3 volts. Doesn't sound like he would see flicker with a 3v drop.
His ch1 averages about 20 amps of current and as high as 128 amps, his ch2 stays on 4 amps with maybe 60 cycles over 16 amps.
But his voltage on both channels are almost the same.
I do see a lot of 3v drops with no amperage increases across both channels. This could be a neighboring house causing this.
Based on the 3V drop, the POCO says all is in spec. Their spec is 5% voltage drop on motor starts (6V). I have some issues with whether they were recording enough or even correctly (line currrents not the same on motor start), so I've talked her into putting the power quality meter back on with parameters set up for recording wave forms and subcycle values.
Don't know of anything I can do on my side the meter (lamp changes are not an option) to mitigate the flickering/blinking. Will talk to my neighbors to see if they notice blinking to help support a change.
thanks for the continued input/comments.
Iron_Ben
Senior Member
- Location
- Lancaster, PA
I'm not terribly impressed with the PMI analysis but I won't worry about that now. #4 aluminum triplex stuns me. 80 or 90 feet of that after the overhead secondaries is too small in my view for a house with a 150 or more likely 200 amp service. Even if your underground run was only 10 feet long it would be too small. We had 5 choices of URD triplex to feed homes with: 1/0, 2/0, 3/0, 4/0, and 350. The smallest I ever called for was 2/0. #4 is begging for flicker trouble.
Here's a rough draft I threw together that you can polish up and send to your engineer's boss. Or not. Good luck!
Dear _______:
I am writing you as a dissatisfied customer. I am displeased with both the electric service at my home (insert address and account number) and your group's response to my issues. I do appreciate that your engineer, Ms. So and So, has been good about corresponding with me on a timely basis and I appreciate the installation of a voltage recorder last month.
My principal concern can be summarized in one word. Flicker. The short term voltage drop (flicker) created when my air conditioner starts is too much. The lights in my house dim excessively. I am an electrical engineer myself. I realize that there will of necessity be a brief drop in voltage when my unit comes on. However this drop is too much. The dimming of lights is more than I am willing to live with. And it is so easily remedied!
The thing to do is to pull out the 90 feet of #4 triplex presently in the 2.5" pipe going to my meter and replace it with larger triplex. 4/0 would be good; a huge improvement. If you stock something like 250 or 350 mcm so much the better. This will cut the flicker down to perhaps 50% or 60% of what it is now as the transformer and overhead secondary impedances will be unchanged. As you know, this is not a "big" or expensive job. I suspect the cost of the new wire is on the order of $200 or so. Two servicemen working together ought to be able to knock it out in an hour or less.
The report from the recording voltmeter you installed indicates 3% flicker, within your company's stated allowable limit of 5%. I must tell you that I don't care if a report labels the flicker at my house as 1% or 10%. It is simply too much. I invite you to come to my house and observe the lights when my unit comes on and tell me you would live with it.
As an aside, your #4 aluminum triplex that feeds my house seems smaller than reasonable. It's "large" enough in that it is able to carry the electric load of the house but because it is so small it is going to be a contributor to flicker and voltage drop issues. With a full load continuous capacity of about 65 amps, it's a questionable choice for my house's 200 amp service. A retired utility engineer I know told me that not only was his company's lower limit aluminum triplex wire size for residential services 1/0, but that he himself never called for anything smaller than 2/0 on an underground service to a house.
In a spirit of compromise I am offering to pay half the cost of the new wire, up to $150. That is how badly I want the too-small #4 upsized.
In closing, I appreciate the installation of the recording voltmeter and the fact that Ms. So and So is always pleasant when speaking with me on the phone. However, I feel I have been more than patient in awaiting a resolution to this flicker problem. Here we are, xxx months after I brought this to your attention and the problem is unchanged. This is unacceptable and falls woefully short of any sort of first class customer service. I need to have my #4 triplex upsized or my flicker otherwise reduced to a reasonable level within two weeks. If you can't or won't commit to this, my next step is to forward this letter to the Public Service Commission for their consideration.
Sincerely,
(Ben)
Thanks Ben, I like your calm but firm demeanor.
And for the record, I was able to capture with my amprobe 111A start current after hard start kit installed.
By the way Ben, I'll include that in the correspondence to show I'm doing everything on my side the meter to rectify the flicker.
Also my service is 200A, and I used 4/0 copper from meter to main panel. I believe 3/0 is typical for 200A installs around here.
And for the record, I was able to capture with my amprobe 111A start current after hard start kit installed.
By the way Ben, I'll include that in the correspondence to show I'm doing everything on my side the meter to rectify the flicker.
Also my service is 200A, and I used 4/0 copper from meter to main panel. I believe 3/0 is typical for 200A installs around here.
Last edited:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Have you had time to run the voltage drop for 70' of #4 Al at that current yet?
(No app on my phone for that...)
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
140821-2135 EDT
The loop resistance for 80 ft of #4 aluminum is about 0.07 ohms. With a change of 100 A the voltage change is about 7 V. One half of this would be seen by a 120 V bulb. Or 3.5 V.
I ran a test with a 60 W 120 V bulb with a series 2.7 ohm resistor. Shorting the resistor produces about 1.5 V change. Under signal known exactly (I know when I short the resistor) experimental conditions I can detect flicker, but you might not detect this reading a book. Run your own experiment with various resistors. I doubt that your power company will do anything about your service lines. Live with the problem, or change the type of bulb, or circuit controlling voltage to the bulb. Don't forget there is impedance in the transformer as well as the service wire resistance.
At my web site http://beta-a2.com/energy.html the first graph shows my line voltage with 1 second averaging and resolution. Around 2000 (8 PM) you see a voltage dip of about 2 V. Might actually be larger with a shorter averaging time.
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The loop resistance for 80 ft of #4 aluminum is about 0.07 ohms. With a change of 100 A the voltage change is about 7 V. One half of this would be seen by a 120 V bulb. Or 3.5 V.
I ran a test with a 60 W 120 V bulb with a series 2.7 ohm resistor. Shorting the resistor produces about 1.5 V change. Under signal known exactly (I know when I short the resistor) experimental conditions I can detect flicker, but you might not detect this reading a book. Run your own experiment with various resistors. I doubt that your power company will do anything about your service lines. Live with the problem, or change the type of bulb, or circuit controlling voltage to the bulb. Don't forget there is impedance in the transformer as well as the service wire resistance.
At my web site http://beta-a2.com/energy.html the first graph shows my line voltage with 1 second averaging and resolution. Around 2000 (8 PM) you see a voltage dip of about 2 V. Might actually be larger with a shorter averaging time.
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