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Old 06-29-2016, 10:52 AM - Thread Starter
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Low voltage electrical problems

Not sure where to post this, so I'll try here.


Has anyone experienced low voltage electrical problems, as in, the voltage coming from the wall? Is it possible or reasonable that now that the weather is hot and everyone is running AC my wall voltage could sometimes drop to 110 volts? My theaters power center has a voltage meter and it lights up yellow when the voltage drops to 110 (and shuts down below that). Last summer it started dropping to 110 randomly, but I never noticed a pattern. Over the winter it stopped and I thought it was a strange fluke. Now its restarted. Before I hire an electrician, call the electrical company, or purchase any new stuff, I thought I would check here for a sanity check.


I think there might be something wrong with the power center. I did in fact test the power coming out of the wall a few times now and it did not read that low on my multimeter. However I've also had trouble capturing the voltage at the right time as I work during the day and can't run over to test the voltage. I just sometimes notice the light is yellow when walking by.


What do you think, is it more likely to be a bad power center rather than a voltage problem in my house? Could I really be getting 110 volts on my line sometimes like that? Should I consider buying a plug in monitor to get more accurate voltage reads on the fly (since multimeters are intentionally designed to not be able to do what I did I had to modify it and it takes time to measure it safely)?
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Old 06-29-2016, 11:29 AM
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Although I don't have a real answer for you, brownouts can be quite common in the summer. I used to work for an electric company and there were times in the summer when rolling brown outs were very common. One of the big pushes was to install cutoffs on the AC unit at individual homes so that at least the AC could be cutoff in the daytime, presumably while everyone in the house was out, and, supposedly, not for more than 4 hours at a time and the incentive was a slight discount.

So, yes it is possible. You might check to see if your house has one of those meters. although I would think you would know if you were on the plan.
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Old 06-29-2016, 11:30 AM
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Likely an issue with your circuit breaker box OR possibly at the utility side/etc.

Next steps depends on your patience and budget. In other words, you can buy a plug in meter (not sure what type, but I'm sure Google has a few ideas) and go that route to see what your mains are supplying. However, that involves time and money.

On the other hand, you could just replace your power distro box (you don't say what kind you have) and see if that "fixes" the issue.

Last, but not least you could hire an electrician to check out your breaker box and see if something is wired funky (or wrong). It wouldn't be more than $100 or so for him to look and give you an opinion (which is probably spot on as this isn't that hard a problem to solve unless it's at the power plant side....).

Dilemma it is!
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Old 06-29-2016, 11:37 AM
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And now that I think of it, my in-laws, who live in a still country-ish area had a problem with the lights dimming noticeably at intermittent times. Turns out, the above ground feed from the pole to the house was rubbing against the side of the house and part of the insulation had come off. Whenever the wind blew hard enough, the wire would sway, contact the house and the lights would dim. They had to get the power company out to replace the entire run from the pole to the house and re-secure to the house.

So, you could have one of many issues.

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Old 06-29-2016, 11:47 AM
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You shouldn't trust the potential readout on the power center unless you've verified it to be accurate against a different, quality meter.

In case it is actually accurate,110 volts is a pretty normal potential anyways. Maybe just nix the power center, unless you can adjust its threshold to something more like 100 volts.

As for what might be causing fluctuations (sometimes 120, sometime 110), your own house's load can be one of the biggest factors. Voltage drop from the neighborhood's transformer to your receptacle might be over 5 volts if you are loading heavily. On the other hand, some municipals struggle to maintain potential, and can easily sag below 110 during peak load times or if there is a grid component malfunction.

Electrical distribution equipment failure (within your home) is very unlikely to be the cause. I wouldn't bother replacing breakers or anything like that in your house.

I would consider yourself lucky; my electricity is usually 118-125 volts, with 123 typical. Light bulbs burn out much faster at these potentials! I think I'd prefer 110-115 haha.
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Old 06-29-2016, 03:07 PM
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The most likely cause is that your power is simply a bit on the low side. 110 is low, but within acceptable tolerances.

A good quality UPS can automatically adjust for under and over voltages. They have transformers with extra taps and will automatically switch to the proper tap if the voltage is too low or high.

You can do a reasonable check with a $10 multi-meter. (Or free with a coupon at Harbor Freight.) It may not be spot on, but it should be "close enough". If you have any doubt about meter accuracy, try different locations (work, a friend's house in another neighborhood, etc.), and try at different times. If you are getting consistent readings that are low, your meter may not be accurate. If your house reads lower than the other locations, it likely is.


Consider getting a Kill-A-Watt EZ meter. They provide a lot of useful information for around $30. They can be left plugged in permanently and can display the voltage, amperage, wattage, cost to operate, etc.
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Old 06-29-2016, 07:18 PM - Thread Starter
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I actually have a $300 Fluke meter that is accurate to the 10,000th of a volt. Not that its needed. I've never measured it as low as my power center says but I also haven't been able to catch it in its warning state. Like I said, I had noticed it a few times. I also didn't plug it into the power center, I plugged it directly into the wall outlet and not the one the center is on, but another on the same circuit.


The plug in monitors are like $20 and I thought if I had that then I could plug it in and in the event of a yellow warning light, run in quick and take a look.


The power center is Belkin I believe, I forgot the exact model. It has 12 outlets on the back and one on the front. Part of the PureAV HT series, not sure if its even made anymore. I think they sell on ebay still for a few hundred dollars, not sure what they cost new, maybe like $500. I don't want to toss it if its good, but I don't want to keep it if something is wrong. I'm sure the meter on front isn't accurate, but...Its giving me a warning light. I've also had a few weird problems with other equipment, like a crown amplifier power cycling repeatedly, and worried it was the low voltage problem or possibly some weird surge problem. Crown said my firmware was bad and that the most likely cause was a power surge or possibly the low voltage problem, which only restarted recently.


http://www.ebay.com/itm/Belkin-Pure-...AAAOSw9~RXJb~O
This looks the same as what I have.
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Old 06-30-2016, 06:48 AM
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We had that same issue in our last neighborhood outside Chicago. The transformer feeding the development was undersized, and houses at the back of the development had low AC voltage problems in the summer. The power company finally replaced the transformer after it blew and caused a three day blackout.

Take pics of your power center's readout and send 'em to your power company so that they check the power in your neighborhood, or house, if the issue is there.
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Old 06-30-2016, 07:12 AM
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I would open the panel and take a reading on your panel's input feeds. See what it says, and maybe have someone turn on the AC while monitoring. See how much it dips. If you're getting a low reading at the panel, it very well may be the power companies issue and should request for them to check power at the meter to verify.
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Old 06-30-2016, 07:20 AM
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Quote:
Originally Posted by harjms View Post
I would open the panel and take a reading on your panel's input feeds. See what it says, and maybe have someone turn on the AC while monitoring.
I'm very comfortable working inside the panel, and I would never, never, never take a reading on the input feeds. Leave that to the power company.
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Old 06-30-2016, 09:29 AM
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Quote:
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I'm very comfortable working inside the panel, and I would never, never, never take a reading on the input feeds. Leave that to the power company.
Understand and thank you for understanding the risks!
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Old 06-30-2016, 11:22 AM - Thread Starter
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I was thinking the exact same thing! I am not going to take a reading in the panel live. I'll let the electric company or a trained electrician do that.
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Old 06-30-2016, 11:37 AM
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Old 06-30-2016, 12:01 PM - Thread Starter
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Not that admitting this will instill any confidence in me on doing this but...


When I was in high school through my entire undergraduate degree I worked in a maintenance department at my fathers business and did a lot of electrical work. At the same time I also had internships at various companies which included Cuttler Hammer and numerous others building and testing certain high voltage electrical devices. I also have over the years built very high power and high current amplifiers and the such.


In that time I've done the following:
-Cut a live electrical line with pliers because I forgot it was live. A breaker saved my life!
-Discharged a massive capacitor array with a screw driver because a PhD engineer told me to. We both underestimated the potential of that cap array and it split the steel screwdriver and shot it out of my hands. I was in more danger from the screwdriver shooting out of my hand and the sparks created than any electrical charge as I was physically very well insulated at the time.
-Discharged a cap array and welded a discharge stick to it. The "discharge stick" was copper and had a resistive load connected to ground. It was simply too much at once and the resistance of the bulb was too low, so it melted the copper at the connection site.
-Accidentally connected the wires backwards on an amplifier connected to a power supply that contained 240,000 uf's of capacitance at 75 volts per rail along with 11 mh of inductance I believe. The amplifier immediately caught fire and threw sparks as soon as the voltage was turned up. Variac didn't save anything. My face was lucky to end up unscathed as I just happened to be looking at my test sheet at the time.
-Accidentally wired an amplifier dummy load for .25 ohms instead of 2 ohms and before realizing what I did had sent through a signal that caused more than 100 volts to swing on the output of an unprotected amplifier circuit and destroyed its output devices along with most of the protection resistors.
-zapped myself attempted to rewire a live outlet because we couldn't find the correct breaker on the subpanels and I didn't want to shut down an entire wing of the facility for a ten minute job. However when I was screwing the outlet back in I accidentally slid the outlet toward the side of the box and caused a short. It tripped a breaker and while I felt something, it was obviously minor.
-Blew up a $50,000 custom built test bench power supply with a QC testing rig I designed and built. I have to say though, it wasn't my fault this time. I intentionally wired it "upside down" so that everything switched in reverse of what was convenient to avoid the possibility of straining the incoming wires and causing a short. The Company president came in and physically spun the switches around which put the stress on them and an hour later the wires did in fact break loose and short out, destroying the supply in the process. It was still considered my fault since my test rig should not have been so easily modified. I was also a 17 year old intern, so I still like to think it wasn't my fault.


While every one of these smooth moves taught me a lesson (and most of those happened when I was under 19 years of age, some even under 18), I still don't really trust myself around household potential voltage anymore. I'm pretty smart but I'm also pretty absent minded and sometimes I'll make dumb mistakes like this. With electrical, that could be my life.


And....After all that I eventually left the field of electrical engineering and earned graduate degrees in an area that basically combines psychology, public health, statistics, and research design. Pretty different and probably for the best.
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