Zarathustra[H]

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Hey all,

I was trying to find the best place to stick this thread, but it doesn't really fit neatly in any subforum, but here goes.

We are in the process of moving in to a new house. I'm setting up my rack in my new server room, and both of my APC Smart-UPS units are spending a lot of time in "AVR Trim" mode, which means they have detected too high line voltage, and are adjusting it down for the equipment.

US line voltage spec is 120V +/- 5%, so a range of 114V to 126V.

I've been monitoring the line voltage using my APC units every now and then. They drift in and out of AVR mode. When the AVR LED's are lit up, I read a line voltage of ~127.5V, which is above spec. The AVR LED's are lit up about half the time. I'm guessing the line voltage is flirting with the upper specification limit.

IMG_20200520_134058.jpg


So, I am neither an electrician nor an electrical engineer (my specialties are in mechanical, industrial and process engineering), but my question is, how much of a problem is this?

Is this a "drop everything, this might start a fire" moment, or should I just count my lucky stars, because higher voltage means lower current which means better efficiency?

I'm not that concerned about the stuff behind the UPS units, but what about everything else in the house?

Appreciate any suggestions, including whether I need to get on the line to the power company ASAP!
 
Last edited:

sinisterDei

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Caveat that I'm no electrician, nor even an electrical expert.

I would call the power company, but first I would check and make sure that it isn't something upstream between you and the power company. You could have some kind of whole house line conditioner or somesuch that might be introducing this voltage variance.

Swings to 127v coming to you is *probably* not that big of a deal. However, if this one facet of your power is fluctuating, it's possible other factors are more fluid than they should be. Swings to 127v probably isn't so bad, but swings below 113v could be. And there is no guarantee that whatever is causing the voltage swings will stop at +/- 7v.

I would be concerned.
 

Kardonxt

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Back in the day it was not uncommon for voltages ~128 to drastically reduce light bulb longevity. I'm not sure if modern LED \ CFL light bulbs have the same problem, but it's probably not great for your appliances. I imagine it also gives you less wiggle room in the event of a power surge.

If you are comfortable with a multimeter I would check at a couple places at the house and the panel. If it all reads high then you should contact your power company. If it only reads high on a couple outlets then you may have a wiring issue.
 

Trepidati0n

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Call your local utility. Sometimes loads change and voltages can shift and they need to re-balance. Not a big deal.
 

Zarathustra[H]

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So, I just upgraded my UPS:es to newer SMT1500RM2U models (damn are they heavy)

These units have better logging capability than my old units.

They have been installed for three days now. On 5 occasions the AVR kicked in for too high voltage.

Max recorded voltage is 127.39v, but lowest recorded voltage is 112.30v.

So it looks like it is fluctuating across the range of high and low, but tending towards the high.

I never had the AVR mode kick in for high voltage in my old house.

I guess I am trying to understand, is this kind of fluctuation normal, or is something really messed up?

I called the power company and reported the high voltage conditions. They told me they would take a look at it, but I don't know what to expect.
 

GotNoRice

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127v should not be dangerous. In Mexico 127v is actually the normal voltage, because higher voltage results in less transmission loss, and 127v is "close enough" to 120v to still be compatible with electronics designed for 120v. The lower transmission loss means that the electric utility company can get away with greater distances between substations. The motivation for doing this also applies here in the US, especially in areas where the grid is stretched thin. The people who are very close to a substation might see 125v+ while the people farthest away from the substation might only see 110v. If they tried to maintain only 120v for people close to the substation, then the people farther away wouldn't even be getting 110v, and the utility company would have to build more substations. So it's not just a matter of them adjusting a knob on their end. They probably won't change their substation configuration just because you complained.

At least there are many devices that really do not care much about the voltage. Electronics using Active PFC for example (most computer power supplies) can handle any voltage between about 87v and 266v (usually listed as 100-240v).
 

tunatime

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If you are getting high and low voltage....you probably have a lose neutral...or your transformer is about to blow...most of the time they have very tight regulation
 

Zarathustra[H]

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If you are getting high and low voltage....you probably have a lose neutral...or your transformer is about to blow...most of the time they have very tight regulation

Hmm.

The electric company sent out a guy there other day. He replaced the connectors on both sides of the line going out to the pole. They were older and smaller than current specs.

It might have helped a little bit. I'm giving it some time, and then I'll grab the before/after log from the ups and see if there is a notable difference.
 

tunatime

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Or just get an online ups 130v won't hurt anything. What's your 240v though? Bet it's it's not 255-260
 

Zarathustra[H]

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Hmm.

Looks like the UPS network management cards can only store 400 lines of log data, and since default is to sample every 10 minutes, that means I only have about 2.8 days of data, all of which is after the power company reattached our line :/

Anyway this is it. Red line is max voltage recorded during the 10min period, blue line is min voltage recorded during the 10 min period.

1600915445268.png


Max voltage recorded during the time period was 127.39v
Min voltage recorded during the time period was 110.8v

Considering the spec is 120 +/- 5% (or 114v to 126v) this means that in less than 3 days I've been out on both the high end and the low end of the spec...

Is this really normal?

I've never had much of a light flickering issue, except for dimmed LED bulbs which flicker like mad.
 

tunatime

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Screenshot_20200923-234615.jpg

Honestly it's borderline but as long as it doesn't change rapidly you should be allright

To see what is going on I need to know your 240v power if you have a solid 240-250 coming in then you have a problem with the neutral somewhere if both if the 240v is chnaging it's a power company problem
 

Zarathustra[H]

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View attachment 282212
Honestly it's borderline but as long as it doesn't change rapidly you should be allright

To see what is going on I need to know your 240v power if you have a solid 240-250 coming in then you have a problem with the neutral somewhere if both if the 240v is chnaging it's a power company problem

Ah. I am less experienced with 240v power. I don't have any fancy tools to monitor it wit.

I could stick my multimeter in there and measure, but it will take some reading. With all those leads I'm not sure which to measure between. Any advice
I think the connector is a nema14-30.
 

tunatime

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I'm assuming this is standard Single phase 240?
You have to take your cover off for this so if you don't feel safe doing it don't do it please......you should see 3 large wires coming in one should have white tape that's the neutral other two are power. take your meter and go form one hot to the next should be 240 range...then go form hot A to neutral then hot B to neutral they should be very very colse.

If you read a soild 240ish form hot to hot but your hot to neutral keeps changing then you have a problem with your neutral.. check them both one will go up as the other goes down if you have a problem.

What cat rating is your meter / voltage range? Need to be rated for at least 300v and as I said if you feel not up to it call someone you can hurt/kill yourself if you mess up
 

Zarathustra[H]

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I'm assuming this is standard Single phase 240?
You have to take your cover off for this so if you don't feel safe doing it don't do it please......you should see 3 large wires coming in one should have white tape that's the neutral other two are power. take your meter and go form one hot to the next should be 240 range...then go form hot A to neutral then hot B to neutral they should be very very colse.

If you read a soild 240ish form hot to hot but your hot to neutral keeps changing then you have a problem with your neutral.. check them both one will go up as the other goes down if you have a problem.

What cat rating is your meter / voltage range? Need to be rated for at least 300v and as I said if you feel not up to it call someone you can hurt/kill yourself if you mess up

I'm going to think about it.

I've given myself the fun little 120v tingle in the past accidentally. I'm fine powering stuff down and wiring it, but I'm undecided if I want to mess with live 240v wires just in case I slip or pull a stupid :p
 

tunatime

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I'm going to think about it.

I've given myself the fun little 120v tingle in the past accidentally. I'm fine powering stuff down and wiring it, but I'm undecided if I want to mess with live 240v wires just in case I slip or pull a stupid :p
Honestly if you watch some YouTube you can probably do it safely as long as you are careful and not stupid about it. Go slow and take any rings off ect and as long as you have insulated probes it's not bad...also have someone watch you with a big pvc pipe or something if you are real worried about it they can knock you off if you get zaped and can't let go.
 

Omegas

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He might have a 240 outlet for his electric water heater or dryer he can test voltage from.
 

BinarySynapse

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I'm going to think about it.

I've given myself the fun little 120v tingle in the past accidentally. I'm fine powering stuff down and wiring it, but I'm undecided if I want to mess with live 240v wires just in case I slip or pull a stupid :p

As long as you don’t go grabbing both hots, you’re only ever going to get a 120v tingle from a 240v circuit.
 
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