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Old 09-15-2011, 10:34 PM   #1
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Voltage drop? Lights dim with load on different circuit.


Hello all, this is my first post and I hope someone is able to give me a little advice.

I am a first-time homeowner - just bought my house back in June - we'll say it's a "fixer-upper" and leave it at that.

I am experiencing a strange problem with the electrical system and I am unsure how to begin troubleshooting. Here's a little background:


House:
- Built 1880's, wiring retrofitted in the '10s or 'teens like all the old houses around here. I am the third owner of the house, believe it or not.
- 2 original circuits still in place but of course circuits have been added/updated throughout the years. Most are real hackjobs.
- 200A 120V/240V service installed in 2005/2006 and it was a very clean/professional installation. Square-D panel with lots of breakers. New meter, service entrance cable, and service drop from pole to house also installed in 05/06.
- We do not use the "old" circuits for anything more demanding than lighting, lamps, nightlights, etc.
- There is only one MWBC (that I know of) and that was installed in 1993 (incorrectly, too - imagine that).


Here's the scenario:
- When something with a heavy load is engaged (vacuum cleaner, deep fryer, washer/dryer, etc.), the lights in the house will dim. Window fans and exhaust fans get slightly slower. This lasts until the load is turned off and then returns to normal.
- It does not seem to matter which room or circuit the load is connected to, behaviour is the same.
- In extreme cases, like when then sump pump kicks on (which is on average 2-3 times per hour!), the voltage drop will be so significant that the UPS in the office flips out, starts beeping, switches over to battery, etc. The sump pump is on a dedicated circuit of its own.
- Also, in two of our rooms (different circuits) the lights will flicker briefly - it lasts for a fraction of a second and some people don't even notice it until I mention it to them. Now other people who live in this area say this happens to "everybody" but we had an apartment just up the street from here and it did not have this issue. The flicker is totally random and sometimes doesn't happen at all.


Work I have already done:
- I have added several circuits (all new cable, devices, etc.) for things like the laundry room, furnace, dishwasher, and a few others.
- Re-torqued all of the connections in the panel and re-seated all of the breakers. - Opened every junction box I could find and repaired a bunch of scary splices and terminations
- Measured voltage at every outlet in the house and they range from 115-119V


I know that's a lot to read but I wanted to post as much info as possible. Does anybody have any experiences, thoughts, places I should start, or things I need to look for?


Thanks in advance for your suggestions! I can post photos of anything you want and can get pretty detailed with more descriptions for you.

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Old 09-16-2011, 05:49 AM   #2
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Voltage drop? Lights dim with load on different circuit.


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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Old 09-16-2011, 09:47 AM   #3
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Voltage drop? Lights dim with load on different circuit.


If it happens to your neighbors also, then I would suspect a bad transformer. Call the power company.
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Old 09-16-2011, 09:53 AM   #4
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Voltage drop? Lights dim with load on different circuit.


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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Old 09-16-2011, 09:56 AM   #5
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Voltage drop? Lights dim with load on different circuit.


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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Old 09-16-2011, 09:56 AM   #6
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Voltage drop? Lights dim with load on different circuit.


Test on the line side of the breaker.
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Old 09-16-2011, 10:05 AM   #7
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Voltage drop? Lights dim with load on different circuit.


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/B00...RYAW2BEAPX43S1
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Old 09-16-2011, 10:10 AM   #8
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Voltage drop? Lights dim with load on different circuit.


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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Old 09-16-2011, 10:24 AM   #9
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Voltage drop? Lights dim with load on different circuit.


Test at lugs.
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Old 09-16-2011, 10:26 AM   #10
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Voltage drop? Lights dim with load on different circuit.


Quote:
Originally Posted by nezwick View Post
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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Old 09-16-2011, 10:28 AM   #11
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Voltage drop? Lights dim with load on different circuit.


Quote:
Originally Posted by nezwick View Post
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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Old 09-16-2011, 10:33 AM   #12
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Voltage drop? Lights dim with load on different circuit.


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.

Last edited by nezwick; 09-16-2011 at 10:37 AM.
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Old 09-16-2011, 11:11 AM   #13
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Voltage drop? Lights dim with load on different circuit.


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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Old 09-16-2011, 11:28 AM   #14
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Voltage drop? Lights dim with load on different circuit.


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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Old 09-16-2011, 11:32 AM   #15
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Voltage drop? Lights dim with load on different circuit.


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

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