# Voltage drop? Lights dim with load on different circuit.



## dmxtothemax (Oct 26, 2010)

This is called a current limit !
It basically means your system cannot get enough current,
When it needs it.
It could be loose connections, ( most common problem )
Or undersized conductors,
It could also be a POCO problem.
A quick test would be this,
Put an accurate volt meter on your main switch/breaker,
Get some one to turn on a heavy load,
If the meter shows signicant change,
Then the problem is BEFORE the meter,
IE a poco problem.

If not it is further down field,
You will have to test all connections from that point
on, untill you find the problem or problems.
Remember it could be several problems all combining.


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## HouseHelper (Mar 20, 2007)

If it happens to your neighbors also, then I would suspect a bad transformer. Call the power company.


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## nezwick (Sep 16, 2011)

Thanks for your reply, *dmxtothemax*! I consider myself a pretty proficient installer but I'm pretty new to troubleshooting.

I will definitely give that a try (testing voltage at the main breaker). I DID NOT reseat the main breaker because there is no accessible means of disconnect upstream of the main and I don't like working circuits hot.

My multimeter is a cheapie digital one from Sears - it has served me well so far but I will see if anybody I know has something a little higher-end.

I had considered calling the utility about the flickering lights when we first moved in, but the cost of moving and doing a couple of major repairs has pretty much broken the bank for now. Several people I talked to said that the utility will charge the customer for working on the service drop and weatherheads because they are owned by the customers around here (rural area) instead of the utility like in the cities. I have not confirmed this for myself but I didn't want to throw up any red flags at the PoCo for being a potential "hazard" and then have to pay an electrician to service anything right now (no offense intended to all you electricians!).

I will report back as soon as I have some results.


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## nezwick (Sep 16, 2011)

*HouseHelper*, I actually have not met any of my neighbours but I might have to take this opportunity to speak to them haha.

I guess I forgot to mention in my original post that the central air is the biggest cause of this "drop" - I always forget we have it because I hardly use it. But back in July when we used it most frequently, it made the lights dim way down. It is a 2.5 tonne unit from 1995.


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## Code05 (May 24, 2009)

Test on the line side of the breaker.


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## Code05 (May 24, 2009)

I recommend this meter to a lot of people. It is basic, but meets general needs. You can probably get a better price. My supply house sells them for $60.00.

http://www.amazon.com/gp/product/B0..._m=ATVPDKIKX0DER&pf_rd_r=01GHSJRYAW2BEAPX43S1


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## nezwick (Sep 16, 2011)

By the way, this is a pic of my panel (prior to my addition of a couple of circuits). Should I just test on the lugs connecting to the main cable?

(Yes I know there are one or two incorrect things going on in there, but nothing major that I can tell).


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## Code05 (May 24, 2009)

Test at lugs.


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## Code05 (May 24, 2009)

nezwick said:


> *HouseHelper*, I actually have not met any of my neighbours but I might have to take this opportunity to speak to them haha.
> 
> I guess I forgot to mention in my original post that the central air is the biggest cause of this "drop" - I always forget we have it because I hardly use it. But back in July when we used it most frequently, it made the lights dim way down. It is a 2.5 tonne unit from 1995.


AC unit dimming lights is common. A vacuum or well pump is not.


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## Code05 (May 24, 2009)

nezwick said:


> *HouseHelper*, I actually have not met any of my neighbours but I might have to take this opportunity to speak to them haha.
> 
> I guess I forgot to mention in my original post that the central air is the biggest cause of this "drop" - I always forget we have it because I hardly use it. But back in July when we used it most frequently, it made the lights dim way down. It is a 2.5 *tonne* unit from 1995.


British?


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## nezwick (Sep 16, 2011)

Alright I just did a quick test with my multimeter.

With no major loads connected, "resting" voltage tested between the left leg (solid black) to the neutral is a stable 118V.
Dehumidifier running - stable at about 116.2V
Sump pump kicks on - voltage drops immediately to between 112.8V-113.2V (fluctuates)
Sump pump finishes pumping water and runs "dry" for about 2 seconds before shutting off - voltage drops to 111V
Sump pump shuts off - voltage returns to 113V and then slowly creeps back up to 118V and stabilises.

Sump pump is from 2004 according to our PO - manufacturer and specs unknown.


British - nah, but I have always had a habit of spelling things the international english way. My teachers back in high school and college gave up trying to correct me.


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## Code05 (May 24, 2009)

I am guessing undersized transformer. Voltages are low, but within limits.
POCO may not do anything. POCO undersizes them all the time.


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## nezwick (Sep 16, 2011)

So what I understand is that the "problem" exists upstream of my main breaker, so a call to the utility is not an unreasonable thing to do? I am happy to know that the likelihood of the issue being mine is fairly low.

Unless, of course, the issue is with my weatherhead/SEC/drop or a connection within my meter box. Then the utility will usually say it's a customer's responsibility. The only thing they seem to take responsibility for is the meter itself, but the enclosure is customer owned. Weird.


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## jbfan (Jul 1, 2004)

What happens when you are on the other leg and the sump pump starts?


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## nezwick (Sep 16, 2011)

"Resting" voltage tested between the right leg (red stripe) to the neutral is a stable 118.0V
Sump pump kicks on - voltage drops slightly to about 117.6V but does not seem to fluctuate
Sump pump finishes pumping water and runs "dry" for about 2 seconds before shutting off - no change - 117.6V
Sump pump shuts off - voltage slowly creeps back up to 118V


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## a7ecorsair (Jun 1, 2010)

Try this too:
With minimum load operating, measure from the left hot to the right hot.
Then turn on as much stuff as you can, lights, AC, dryer if electric, and any other appliances. 
Read from left hot to right hot both above the main breaker and below the main breaker.


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## nezwick (Sep 16, 2011)

Alright here are my readings for *a7ecorsair*'s request:

Minimum load (pretty much the only thing still running is refrigerator, minifridge and fishtank): 233.5V

Then I turned on every single thing in the house except for the central air because it has already been prepped for winter and covered. This includes: every single light and floor lamp (approx 24), range hood, 2 box fans, bathroom vent, 1875W hair dryer, toaster, microwave, gas clothes dryer, washing machine on spin cycle, furnace blower, HDTV, 2 game consoles, 2 MacBooks charging, outdoor flood light, and a 1500W work lamp. The above mentioned fridges and fishtank remained on. I also started the sump pump.

Reading with all of that load on and sump pump running: 223.7

A difference of 9.8V across the two legs.

What does that tell you?


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## Techy (Mar 16, 2011)

transformer sounds too small if the voltages between legs and neutral stay consistent


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## dmxtothemax (Oct 26, 2010)

The change in mains voltage of 10v is not too bad,
But it does point to the problem being a poco problem.
There simply is not enough power available from
the local grid.
You should contact a good electricain and get him to verify your findings, then contact poco and request an upgrade in available power.
They might have to upgrade the local transformer.
But they wont do it unless someone requests it first.


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## a7ecorsair (Jun 1, 2010)

The 233 volt reading is good so the drop you see is all yours. Do you have a pole mounted transformer? If so, how many services are being fed from it?


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## nezwick (Sep 16, 2011)

Yes, it's a pole-mounted transformer, right across the road from the house. I will have to check how many other homes this transformer services tomorrow in the daylight. There is also a small commercial building next door (warehouse) though I'm not sure if it is connected to "our" transformer or not. It is close enough in proximity to our house that it just might be.


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## AllanJ (Nov 24, 2007)

A significant voltage change due to one appliance (even a heavy draw item) in your house is something not upstream of the pole transformer. No one appliance in your house can affect the entire grid that much.

117.6 volts, sump pump turns off, voltage slowly creeps back to 118.0 volts.
I think that this difference is too small to have any meaning.

Is the differential (more correctly difference) in voltage (233.5 vs. 223.7 or 9.8 volts in your case) the same if you did the same test but measured between the breaker screws of two branch circuits' breakers one on each side of the line? We want to see if any additional voltage drop is happening within the main breaker or the bus bars under it which could mean a deteriorating connection in the panel.


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## nezwick (Sep 16, 2011)

The only reason I placed so much focus on that sump pump is because that seems to be the appliance which causes my UPS to flip out most of the time. If I remember correctly, the central air would do it too.

The crazy thing is, today when I was doing all of this testing, even with all those loads on, I didn't hear one peep from my UPS. The lights still dimmed and the most noticeably affected things were the range hood and the sump pump, which both operated more slowly/quietly with the heavy load on the house's electrical system.

I'm still totally confused. I understand that my little sump pump will not affect the grid all that significantly - and I also know that I need to go ask the neighbours on the same transformer as me if they experience similar dimming of lights and slowing of fans when a load is applied. I can tell that the slightly smaller house to the North has central air and a gas furnace, so they may be a good comparison to mine.


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## dmxtothemax (Oct 26, 2010)

Dont forget you also have to consider,
What else is running off that one transformer at the same time.
If the mains has dropped off, and is sitting close to the switch over
point for the ups, then almost anything could be enough to 
trip it over.

I would set up my volt meter,and monitor the mains variations,
use a pen and paper and log them, say every 30 mins.
You will then see if there is any pattern to it.

But remember what is happening at other houses 
that are on the same tranny, could play a part in the problem,
especially if it is a poco problem.

But once you can see a pattern to the problem
then solving it will be that much easier.


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## nezwick (Sep 16, 2011)

AllanJ said:


> Is the differential (more correctly difference) in voltage (233.5 vs. 223.7 or 9.8 volts in your case) the same if you did the same test but measured between the breaker screws of two branch circuits' breakers one on each side of the line? We want to see if any additional voltage drop is happening within the main breaker or the bus bars under it which could mean a deteriorating connection in the panel.


Sorry, *AllanJ*, I did not notice this part of your post.

Tomorrow, I will perform the same test as before and measure on each individual leg.


*dmxtothemax*, I was not home very much this weekend to monitor/log the mains voltage but I will try to get this done at some point.


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## nezwick (Sep 16, 2011)

So I know it's been a long time since I've posted here, but I've honestly had more pressing things to deal with the last few months. I've made progress and didn't want to leave you hanging any longer.

I finally called the utility about this today. The linesman who came out made a startling discovery!

He stood in my yard and was like "where's the transformer for your house?" - of course I had no idea, so he was looking up and down the block until he found one WAY off in the distance. He called his dispatcher to confirm, and sure enough that was our transformer. Here's the kicker:

It's a 20 kilovolt transformer (which, according to the linesman, is supposed to serve 6 or 7 households).

It is currently serving TWENTY FOUR households! Haha! Basically my entire street is on the same undersized transformer, and we are close to the "end of the line". Got to love the infrastructure out here in rural PA.

The linesman called it in, and my work order was escalated in order to get a larger transformer (or multiple smaller ones) installed to upgrade our street.


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## dmxtothemax (Oct 26, 2010)

Thanks for the update !
Yes the tranny is too small for 24 houses !
And its a 20Kw tranny not a 20Kv tranny.
Sorry to nit pick !
I am surprised the tranny has lasted with such a load.
Maybe this is why tranny explosions are so spectactular!


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## nezwick (Sep 16, 2011)

Well I keep calling the POCO back several times a week to see when they plan to replace the transformer, but I keep getting the "it's in our system, we'll get to it" response. I'm gonna keep bugging them until they finally fix it.

My first thought was to fire up up a bunch of space heaters, air conditioners, refrigerators, and a welder at my house - and have my next door neighbour do the same - to see what kind of problems we can cause. I have a 200A service and the neighbour has 100A - our maxed out services plus the additional loads of the rest of the houses on the block should get the POCO's attention!


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