How dangerous is low voltage?

[Wade Lippman]

Like everyone else, we are having a heat wave. I live in an area of mainly summer cottages, so everyone is out today with their A/Cs running constantly. I checked voltage at 7pm and it was 106.5v, which is a little alarming. In the winter it is 125v and typical summer is 115v, but I have never seen 106.5v. Is that safe for electrical devices?

I am mainly concerned about the A/C. Trane has absolutely no information on it, but I have read a general article that seemed authoritative that A/C is designed to be 230v and can tolerate 10% up or down; so it is good to 207v. Does that seem right? I checked the A/C nameplate and it says 230v.

By 8pm it had gone up to 110v and by 10pm 112v. I have asked my wife not to do laundry or use the dishwasher except early morning or late evening when the temperature is lower and the voltage higher. I don't know what else I can do; turning off the A/C doesn't affect my voltage.

They are gradually tearing down the small summer cottages, many of which aren't airconditioned, and putting up huge ones; apparently the utility hasn't figured out they have to increase the supply capacity.

[Mike Cutler]

Wade

The spec for us, I work for a major utility, to consider the lines degraded is 106vac. 106.5vac with a non calibrated meter would have me calling someone. You're starting to approach "brownout" voltages.
Lower voltages are not so much "dangerous" as troublesome. The breaker will still trip on an over current condition.
Lower voltages are particularly troublesome for motors as it will increase the amperage for the same given load.
What is the voltage coming into the house,and do you know the current draw on both legs?

[Steve Rozmiarek]

Wade, I lived in an irrigated farming area, and in the summer when the army of pump motors is using up power, the voltage would drop that low for a day or two. I'd have trouble with the voltage dropping low enough that the control circuits on the pivots would shut them down because the stepped down voltage was too low. Every year the power company would eventually "turn up" the voltage a little, and fix the problem. You are probably furthest from a substation, and they may not even know the problem is happening. Worth a call anyhow as they can do a little to remedy it, short of major upgrades. I never saw a household electrical component failure, but it was hell on the 100hp motor starters, I became really good at replacing contactor coils.

[Mark Bolton]

While it may be anecdotal or incorrect information I have always been told and under the assumption that low and high voltage is hell on any rotating motor as well as resistive load (high voltage). I have posted about this here in the past as it seems nearly our entire state is operating on what seems to be antiquated infrastructure that the utilities simply dont have the budget or intent to upgrade. So Mikes statement about +/- 10% is what our utility is telling me. For 20 years I have brought it to their attention that various places in my local area (when I was operating as a general contractor) would see anywhere from 109 to 129-130+. When you would speak with an engineer who was sassy or didnt really care he would tell you directly that the older lines out in the hollows are not going to be upgraded until failure because there just isnt enough money from the few houses at the end of the line to justify the cost so they are over-driving at the front end to get them power at the end of the line. For this reason all of our electrical supply houses (not home centers) only stock 130v filament bulbs with regards to incandescent because the standard bulbs simply dont last. I have heard from many a homeowner who called me wondering about their house wiring in a home we built for them because their bulbs lasted for years and then all the sudden every bulb they put in only lasts for a couple months. When I ask, they are all buying bulbs at lowes, home depot, walmart... Even LED's dont last for squat from those places.

When we installed the CNC here on the main road in the small town we suffered issues with high voltage. Contacted the utility, they installed a logging meter, and told me the 10%+\- line again. So they are allowed 24V over and 24V under. When they pulled the meter and sent me the info, the meter had held consistently at 262-263 volts. We wound up having to install a transformer to reduce the voltage to the CNC but the rest of the shop bears the burden of that over-voltage condition all day, every day. As do all the neighbors with their HVAC motors, fridge compressors, washers, dryers, dishwashers, and lightbulbs.

Its insane what the utility company is costing the average consumer with failed appiances, control circuits, and so on.

[Rollie Meyers]

Perhaps a complaint to the public utilities commission would be in order??

[Jim Koepke]

One of my employers in the past was a company that made power line management equipment.

Some of the power company higher ups have no idea of what is taking place in the networks of which they are in charge.

When a lot of motors are running there can be a voltage drop due to phase shifting between the current and the voltage. A way to correct this is to switch in a bank of capacitors. Motors are inductive loads and cause a phase shift opposite of what a capacitor causes, hence a counter acting phase shift will bring the voltage back up a bit.

Not all power companies have engineers with the ability to explain this to the bean counters.

In effect there is someone who doesn't know about what is going on taking advice from someone who only cares about the money with no one who knows how to keep the customers happy.

You might get some attention if you told them you notice the meter spins a lot slower when your lights are dimmed by the voltage drop.

jtk

[John C Cox]

Yes - it's bad... The issue is that power = Voltage x Amps.

And so if your voltage drops 10% - the amps have to increase 10% to keep up....

But resistance voltage drop = amps x resistance.... And Resistance = Heat...

And this starts a death spiral....

Increased Amps cause heat in wires - and Heat causes resistance which further drops Volts... Which further causes Amp draw to increase.

But - YES start by contact the utility and complain. It could be as simple as a badly corroded connection where the line comes off the transformer at the road, corrosion on the feeder running to your house.... Or it could be bad connections in your breaker panel or undersize wires in your house.

If you have access to a UV/thermal camera - scan your circuit breaker and see if you have any hot spots - especially on the main. Do the same with the AC panel.... Also you can scan the feeder running to your house and the transformer....

If the issue is on your end - say an old rusty main in the breaker, hire an electrician to sort it out...

Definately contact the utility.... As they may well have services available to test your house electrical for "hot spots".

If they check all this stuff and don't find anything or already know about the problem - contact your state house representative and your State Public Utility Commission - often those guys tie the hands of the utility unless they have complaints from voters....

This may be a very good reason to consider looking at a Solar installation... It can help reduce demand on the utility during hot summer Peak hours. Which helps alleviate some of these types of problems. But I would start by contacting the utility to see if they can sort it out.....

[Alan Rutherford]

... Lower voltages are particularly troublesome for motors as it will increase the amperage for the same given load.... ...leading to overheating and burning out motor windings. I learned this years ago when I plugged a drill into several household-quality extension cords to reach 100' or so from the outlet. The drill stopped working. I took it back to Sears and the salesman took it apart to show me the melted windings. Then he replaced the drill. That will give you an idea how long ago it was. I wouldn't run anything with a motor much below 110 if I had a choice.

[Wade Lippman]

I checked 4 other houses on the street, at least one was on a different transformer. They are all the same.

My neighbor has a really large electrical infrastructure company; he was unaware of the problem, but said he would look into it. I expect they are more likely to listen to him than me; whoever they are.

[Rod Sheridan]

As others have said +- 10% is normal tolerance so that's 108 to 132 volts.

I would call the Utility, they need to change transformer taps or switch in more capacitors..........Rod.

[Mike Cutler]

...leading to overheating and burning out motor windings. I learned this years ago when I plugged a drill into several household-quality extension cords to reach 100' or so from the outlet. The drill stopped working. I took it back to Sears and the salesman took it apart to show me the melted windings. Then he replaced the drill. That will give you an idea how long ago it was. I wouldn't run anything with a motor much below 110 if I had a choice.

Alan
It's interesting that you mention the extension cords.
A decade or so back I gave a safety topic lecture on extension cord usage in the plant. I actually learned quite a bit about them preparing for it.
At that time, there was no UL testing for plugging one extension cord, into another. They may still not test them that way. We used to do it allthe time at work also, plug one cord into another.
The best example I saw for lower voltage, and driving current, was on a 1HP electric chain hoist. One of the guys thought he would graft an extension cord onto it to increase the distance from the control handle to the hoist. The hoist was over a pool, and after just a minute or so after he started using it, the cord caught on fire at the hoist, and fell into the pool, live.
We were all a lot younger then, so we laughed at him more than we should have. Particularly because at the time he was the only one of us that had kept his license active and therefore he was really ribbing us about being the only one "qualified" to modify the cord/tool.
It was a valuable lesson I've never forgotten.

[Marc Jeske]

Wade - I did not see in your post WHERE you took the voltage reading.

Read the voltage at the line side of your main breaker (the wires that feed it from your Electric KW Meter) ), and then ALSO at the AC ckt.

If you can pull out the plug just the tiniest bit, you would ideally read the volts AT THE PLUG while the compressor is running.

As John C said in the middle of his post.. you need to confirm if there is an inappropriate voltage drop from a poor connection IN YOUR system, your responsibility, OR if it is low incoming, hence POCO responsibility.

We spent some time in a counrtry home, big window AC would pop the main 100 breaker.

Turned out loose connection on load (output) side of breaker had over the years heat aged the internals, and/or just plain running hot due to loose connection, leading to nuisance tripping.

Replaced main breaker, all immediately fixed.

Marc

[Wade Lippman]

Wade - I did not see in your post WHERE you took the voltage reading.



I took it at a box on the panel box; with and without the A/C on. It was the same either way.
I also took it at 4 neighbors; they were about the same.

[Wade Lippman]

We got down to 103.5v today and then it went to 41.5v. Interestingly, my HVAC fan kept running; though I shut it off immediately. Maybe only one leg was reduced?
They say we will have power restored in 5 hours. 5 very hot hours.

Last year the same neighborhood did they same thing. Apparently they didn't fix it very well.

[Mike Cutler]

We got down to 103.5v today and then it went to 41.5v. Interestingly, my HVAC fan kept running; though I shut it off immediately. Maybe only one leg was reduced?
They say we will have power restored in 5 hours. 5 very hot hours.

Last year the same neighborhood did they same thing. Apparently they didn't fix it very well.

41.5!!!! There are no current capacity deficiencies alerts for NEPEX, or NY. You should not be having reduced voltages. I promise I'm putting enough on the grid for you. ;)
Wade, you really need to get someone out there to look at this for you. Either the power company is really doing you a disservice, or you have something very wrong with your electrical system.
Is there any way you can individually read both hots and the neutral? Don't do it, if you can't do it safely. It would just be interesting to see if your neutral is way off balance.

[Wade Lippman]

Its not me! 300 of my closest neighbors are down also. I presume they have 41v also, but I don't know that.
Maybe the two problems are related, though I doubt it.

389072
I checked and both legs are 41.5v.

Got power back and it is still 106v. I was kinda hoping that fixing what ever caused the outage would also fix the low voltage; but guess not.
I will call them next week and they will tell me there is nothing they can do about it.

[Wade Lippman]

Lost power over night. And again now. Who knows... maybe they will actually fix it this time.

Got power back at 1am. 109v argh
Lost power at 1:30; got it back 30 seconds later. 106v. double argh
Lost power at 2; got it back 30 seconds later. 118v. Huh!!

It is 122v now.
Maybe they fixed it, or maybe everyone is still asleep and it is only 68 out, so no A/C.

[Mike Cutler]

Wade

That timeline is hopefully indicative of line maintenance going on.
Good luck, that's a tough spot you're in.

[John C Cox]

I was thinking about you and this post on the night of the 2nd.....
i was out in the shop and all of a sudden - the dehumidifier starts blinking and the lights start flickering ... Then bonk - dark....

So I checked the breakers - nothing there... Got out the meter and started poking around.....

1 entire leg of the 120 service was down.. House and shop both...

11:35pm to 12:05 AM.... At the main power coming in... I had the volt meter in the outlet when it camr back on... Very nice orderly ramp up over about 2 minutes from 0 to 115v.. Groan..

Called them up the next day - Oh... No problems on our end.. Nobody else reported it (of course not - it was midnight...).

Yeah... So thanks for single phasing my AC and shutting down half of everything in the house and shop....

I really need to figure out some sort of power monitor for the incoming power - to log how often they are single phasing my AC....

[Wade Lippman]

It hasn't been below 117.9v since the last outage. Hopefully that means it is fixed. We will see on Sunday when all my neighbors are here and it is 90.

[Perry Hilbert Jr]

The Power companies are stuck between consumer watchdogs that pitch a fit over everything that might make rates go up and those who need fewer brown outs and outages. Ten years ago, we were suffering an average of 10 days per year without electricity due to outages. Not just due to high winds and ice storms. Idiots who plant trees under or so close to the power lines that in 20 years the trees are in the wires. And there is no remedy for such stupidity under current law. I think all residential and commercial property owners should have to reimburse the power company for trimming their trees away from the lines, instead of passing the cost on to all consumers under the current practice.

[Bill Dufour]

I believe the NEC code does not apply below 50 volts. So doorbells and phones are exempt.
BILL D.

[Mike Henderson]

I was thinking about you and this post on the night of the 2nd.....
i was out in the shop and all of a sudden - the dehumidifier starts blinking and the lights start flickering ... Then bonk - dark....

So I checked the breakers - nothing there... Got out the meter and started poking around.....

1 entire leg of the 120 service was down.. House and shop both...

11:35pm to 12:05 AM.... At the main power coming in... I had the volt meter in the outlet when it camr back on... Very nice orderly ramp up over about 2 minutes from 0 to 115v.. Groan..

Called them up the next day - Oh... No problems on our end.. Nobody else reported it (of course not - it was midnight...).

Yeah... So thanks for single phasing my AC and shutting down half of everything in the house and shop....

I really need to figure out some sort of power monitor for the incoming power - to log how often they are single phasing my AC....

The way 120 and 240 volts is provided to you is from a center tapped transformer. The voltage across the outside lines of the transformer is 240 volts and the voltage between either outside and the center tap is 120 volts. The primary of that transformer is connected to a single phase (two wire) high voltage circuit.

If you lost one of your 120 volt legs, the problem is almost certainly in the connection between the transformer and your service panel. It's possible that the transformer failed but, if it did, the power company would have to replace it and you'd see them doing it. I doubt if the transformer is failing on one leg intermittently.

If the high voltage to the primary of the transformer was lost, you'd lose all of your power, not one leg. There's nothing the power company can do on the high side of the transformer to cause you to lose one 120V leg.

I'd check every connection you can get to in that link. If you're sure the problem is not on your side of the meter, if you lose one leg again, get the power company out there as soon as possible so they can check their wiring from the transformer to your meter.

Mike