Mains Voltage Control

[mubs]

I need help from EE types for an electrical problem.

We moved to a different apartment in February. Even since, I have had problems with electrical appliances & gadgets dying or misbehaving. I suspect this is what killed my motherboard recently, and why my UPS acts strange sometimes.

It appears the voltage here is always excessive. My multimeter reads 290V most of the time. This morning it read 320. It's supposed to be 220-240V.

Later, the building electrician brought his clamp meter that read lower; 250 vs mine at 282, both measured at the same time.

He claims there is no problem, and that my meter is defective, but I disagree. Maybe my meter reading is excessive, but when mine read 320, his would have read about 280, which is still too high.

The question is, what can I do to manage this at my end?

Worst case max concurrent consumption would be about 6.5kw (at night with 3 a/cs + fridge running, or in the morning with 3 electrical water heaters on + fridge).

Next year we are planning to move to another city where the problem is likely to be the opposite; low voltage.

There are cupboard sized whole-house voltage stabilizers, but they take up too much space and cost a bomb.

Are there alternatives? Any information, pointers, links would be greatly appreciated.

Thanks.

 

[Chewy509]

IIRC, you're in India? - the spec is "Residential power supplied in India is two wire 220 volts, permitted variation 6%, and maximum load 40 amperes."

220V + 6% = 233.2V
240V + 6% = 254.4V - I would consider 250V to be high even if the local area rating is 240V, especially if you're noticing spikes above this.

Basically either a high quality Line Interactive or online UPS for critical components will be it, if they can't fix in the actual feed-in to the house.

 

[MaxBurn]

Looked at a couple random chargers I have here and they are all marked 240v tops. Assuming yours are the same that's an issue.

There is a step down transformer up stream somewhere that needs to be retapped. They are adjustable within reason but nothing you can do about it, this is a utilities problem. Need to get in touch with whomever provides the power and file some complaints. Thing is they may be intentionally doing this because of a bad grid in your area, there are pieces of the grid further away from the feeder that are low because of line loss and you just happen to be near the feeder. So they might look at it and say that's the best we can do.

Time of day is also a factor. I've seen some industrial buildings in bad areas that ramp up to 520 on a 480 feed after hours when no one is working, quite high. But it's interesting to watch between 6 to 8 am it just drops right down to where it should be.

So yeah, some sort of true online UPS will help the computers and other delicate stuff but you still can't run the whole house off of one.

Edit:
What kind of building? You all might have your own step down transformer that could be retapped. If so have the building guy come back at say 6AM and measure. Or determine yourself what time is the peak and have him come back then.

 

[Howell]

Can you get your ups to give you a over/under voltage report over time to prove the source needs to be fixed?

What you are looking for is called a line conditioner.

 

[jtr1962]

It's hard to see how your meter reading could differ so much from the electrician's. Even very cheap meters usually read AC volts to 1% or so accuracy. The only way the reading could be that far off is if the voltage differs significantly from a sine wave. If that's the case then you have even larger problems than high voltage. I personally don't trust clamp meters to measure voltage. They're really designed to measure current. If you can try another multimeter (not a clamp type), see if the reading is close to what you're seeing on your meter. If so, then I'd bet the electrician's meter was the one giving an incorrect reading.

In any case, modern PC power supplies are usually designed to accept a wide input voltage range, often something like 87 to 264 VAC. They can probably deal with minor overvoltages for short periods. 320 VAC might be a problem but often such a high overvoltage will either blow a fuse in the supply or trip a circuit breaker (if the power supply has one). Usually it will not allow an overvoltage to reach the motherboard. It's more likely that voltage spikes (these can reach thousands of volts) may have caused your old PC to fail. Some of these will pass right through even the best protection. In any case, I would probably be looking into a line conditioner if my local AC power was a bad as yours seems to be. If it really is 320 VAC, then this needs to be corrected ASAP by the electrician. Not only will that kind of voltage kill a lot of equipment, but it might cause arcing or shorts on wires where the insulation is marginal to start with.

 

[mubs]

Can you get your ups to give you a over/under voltage report over time to prove the source needs to be fixed?

What you are looking for is called a line conditioner.

I don;t think my USP will geive me a report; perhaps, I'll have to look into it. I haven't hooked up my UPS' monitoring line to my new PC and installed the APC monitoring sw yet. Will do that tomorrow. That should at the very least give me a snapshot look at various times.

 

[mubs]

IIRC, you're in India? - the spec is "Residential power supplied in India is two wire 220 volts, permitted variation 6%, and maximum load 40 amperes."

220V + 6% = 233.2V
240V + 6% = 254.4V - I would consider 250V to be high even if the local area rating is 240V, especially if you're noticing spikes above this.

Basically either a high quality Line Interactive or online UPS for critical components will be it, if they can't fix in the actual feed-in to the house.

My PC has an APC Back UPS RS1500 line interactive UPS is front of it. Oddly, the voltage is the same at the raw wall socket or coming from the UPS. Right now it's 313VAC!

 

[mubs]

Looked at a couple random chargers I have here and they are all marked 240v tops. Assuming yours are the same that's an issue.

There is a step down transformer up stream somewhere that needs to be retapped. They are adjustable within reason but nothing you can do about it, this is a utilities problem. Need to get in touch with whomever provides the power and file some complaints. Thing is they may be intentionally doing this because of a bad grid in your area, there are pieces of the grid further away from the feeder that are low because of line loss and you just happen to be near the feeder. So they might look at it and say that's the best we can do.

Time of day is also a factor. I've seen some industrial buildings in bad areas that ramp up to 520 on a 480 feed after hours when no one is working, quite high. But it's interesting to watch between 6 to 8 am it just drops right down to where it should be.

So yeah, some sort of true online UPS will help the computers and other delicate stuff but you still can't run the whole house off of one.

Edit:
What kind of building? You all might have your own step down transformer that could be retapped. If so have the building guy come back at say 6AM and measure. Or determine yourself what time is the peak and have him come back then.

Max, there are about 450 apartments in this complex. I'm absolutely sure we have our own transformer(s) on premises. Getting the utility to do it is out of the question; it'll be easier for me to pluck my hair and teeth out one by one. Retaping ours is a long shot too; I'll have to prove that there is a problem in the first place, which is in dispute with the apartment electrician using his meter that shows a lot less. There is no quick and easy solution outside my home, which is why I was wondering what I could do that is in my control.

 

[mubs]

It's hard to see how your meter reading could differ so much from the electrician's. Even very cheap meters usually read AC volts to 1% or so accuracy. The only way the reading could be that far off is if the voltage differs significantly from a sine wave. If that's the case then you have even larger problems than high voltage. I personally don't trust clamp meters to measure voltage. They're really designed to measure current. If you can try another multimeter (not a clamp type), see if the reading is close to what you're seeing on your meter. If so, then I'd bet the electrician's meter was the one giving an incorrect reading.

In any case, modern PC power supplies are usually designed to accept a wide input voltage range, often something like 87 to 264 VAC. They can probably deal with minor overvoltages for short periods. 320 VAC might be a problem but often such a high overvoltage will either blow a fuse in the supply or trip a circuit breaker (if the power supply has one). Usually it will not allow an overvoltage to reach the motherboard. It's more likely that voltage spikes (these can reach thousands of volts) may have caused your old PC to fail. Some of these will pass right through even the best protection. In any case, I would probably be looking into a line conditioner if my local AC power was a bad as yours seems to be. If it really is 320 VAC, then this needs to be corrected ASAP by the electrician. Not only will that kind of voltage kill a lot of equipment, but it might cause arcing or shorts on wires where the insulation is marginal to start with.

jtr, thanks for the inputs. I always thought my multimeter was reliable, but numbers now are so off the wall I'm beginning to doubt that it has become defective (but how?). I need to get another / better one for my own peace of mind and credibility, and to show the clowns here. I was thinking of a clamp type so I could measure current too, but your comment that they are not reliable for voltage gives me pause.

The problem is convincing them there is a problem; since if there is a problem, they have to solve it, so they're insisting there isn't any.

Please see my earlier comment about the UPS out and raw mains voltages being the same. I don't know how to explain that. So far my PC has died and one electric water heater has died twice. All a/cs and the fridge have dedicated voltage stabilizers in front of them, but I measure dthe output of one just for grins, and like the UPS, it showed the same voltage behind and in front of it. Go figure. There are no fuses in the distribution panel, only circuit breakers, and none has ever tripped.

An EE friend of mine here offered the following suggestions:

· First thing to check is whether the 3 phase supply has been properly connected at the meter stage. Sometimes a “floating neutral” can create inordinately high voltages

· If your house is wired over 3 phases, check the voltages across all the phases with respect to neutral. Readings should be in the range of 220V to 240V max.

· Check if someone in your supply circuit has installed one of those “electricity savers” which are effectively capacitor banks. Careless installation leads to voltage inflation

· If you do have to buy voltage stabilisers, try for the servo controlled one (but buy only for critical equipment). The rest of the makes are actually piece of crap meant to give you psychological comfort.

· Check with your neighbors if they have the same problem as yourself. Their equipment has to be busting as well.

 

[DrunkenBastard]

My PC has an APC Back UPS RS1500 line interactive UPS is front of it. Oddly, the voltage is the same at the raw wall socket or coming from the UPS. Right now it's 313VAC!

IIRC you can set these to do a buck/boost at a range of different settings (thru the software or DIP switches), however I can't imagine it delivering 313VAC without switching over to battery and giving you less. My first recommendation would be to get/borrow another multimeter to verify your present numbers.

 

[Howell]

It has been a long time since my EE classes but I think AC and DC voltmeters/settings are not interchangeable. just a thought to check.

 

[jtr1962]

Please see my earlier comment about the UPS out and raw mains voltages being the same. I don't know how to explain that. So far my PC has died and one electric water heater has died twice. All a/cs and the fridge have dedicated voltage stabilizers in front of them, but I measure dthe output of one just for grins, and like the UPS, it showed the same voltage behind and in front of it. Go figure. There are no fuses in the distribution panel, only circuit breakers, and none has ever tripped.

Most UPSes don't stabilize the line voltage so it's not surprising the voltages are the same. Usually UPSes will condition the line, meaning filter out surges and spikes, but won't reduce overvoltages. The fact the two electric water heaters died points to an overvoltage problem. Resistance heaters are usually pretty robust unless subjected to overvoltages. Since it seems fixing the problem at the source isn't possible, you need to buy a voltage stabilizer. I suspect the "voltage stabilizers" on the a/c's and fridge are nothing more than line conditioners. Usually a voltage stabilizer large enough to run an AC or fridge will be fairly big and heavy due to the transformer. If they're not, then they're most likely not voltage stabilizers. The fact that these appliances haven't had issues might be due to the fact that you run a few ACs at the same time. That could drop the line voltage enough so it doesn't harm AC motors (which are actually fairly robust anyway). A real voltage stabilizer will keep the output to 240 VAC plus or minus 5 or 6 percent (or 120 VAC in the US).

On the clamp meter, most that I've seen seem designed to measure current only. I just don't trust non-contact measurements for voltage.

 

[MaxBurn]

Good online UPSs will match frequency and to a certain extent voltage to the input. This aids their transferring to bypass in a fault condition or just normal operation and initiating a load transfer.

 

[LunarMist]

I don't have much to add, but you can't do much in a rental. Get a good conditioning UPS or two.

 

[mubs]

It's kinda painful for me to quote each person and irritating for the readers, so I'll consolidate my replies.

DB, getting another multimeter is the first priority. I don't even know what I'm dealing with otherwise.

Howell, my multimeter has a rotary switch that lets me select multiple ranges for each of DCV, ACV, DCA, ACA and Ohms. I have to presume the internal circuitry is geared for handling the measurement type and range.

jtr, in the old days, the "voltage stabilizers" were huge, incredibly heavy boxes. These days they are compact, measuring a few lbs and 4 x 7 x 10". I have to agree they are merely window dressing. The guess the real ones are servo voltage stabilizers. The thing I'm puzzled aboput is, the circuit breakers don't trip; not a single light has fused; TV (used extensively by the family and not protected) hasn't conked out. But ceiling fans have had problems running hot and wearing out.

BTW the clamp meter the building electrician used had probes he used to measure the voltage by shoving them into the wall socket. So it was measured by making full contact with the mains.

Fluke has an Indian subsidiary with single office and apparently their products are sold only through that office (no retailers or distribution channel). No website for that subsidiary either; only a phone # and an email address. Today is a festival holiday and they will be closed. I have to call tomorrow and ask for price. I'm suspecting it'll be astronomical. I'm not going to spend $400+, even if it's a Fluke.

At the very least I think I should get a servo controlled voltage stabilizer to put between the mains and my UPS. The problem is finding a well-made, reliable one locally; I just don't have the information. I'll have to ask around.

Thanks all.

 

[mubs]

I broke down and bought a Fluke 115 True RMS DMM; I really didn't need the expense at this particular time, but what to do! It was the cheapest True RMS Fluke I could buy here.

Repeated measurements at various times of the day show a max of 248 VAC and a min of 235 VAC. Frequency ranges between 49.5 and 50.5 Hz.

So I guess things are ok. Measuring with my old DMM shows 300 - 320 VAC! I guess the old one is kaput. The change battery sign is on, and I guess this is why the readings are off. I can't change the battery because two screws keep the back cover on, and are located deep inside small dia holes with an odd size Phillips head and are screwed on super tight. I got one off, but stripped the head of the other. I don't know if it's worth sawing off the lower portion of the back with a Dremel to open it, now that I have the Fluke.

I still have to do the other checks with the Fluke, like checking for proper grounding at all the outlets, etc.

Thanks guys for the advice!

 

[MaxBurn]

Fluke is good stuff, won't let you down. For work I have a 77 III and a 77 V, no 123 any more though. Only thing that goes bad on them is the cables and that takes some serious use. We have to calibrate them every year and they never come back from cal saying anything was done, never out of cal.

There are some outlet checkers with like three or four lights that tell you if the hot is on the right side and if the ground is good, handy.

 

[LunarMist]

Fluke is good stuff, won't let you down. For work I have a 77 III and a 77 V, no 123 any more though. Only thing that goes bad on them is the cables and that takes some serious use. We have to calibrate them every year and they never come back from cal saying anything was done, never out of cal.

There are some outlet checkers with like three or four lights that tell you if the hot is on the right side and if the ground is good, handy.

I have an ancient 8060A and it still works. I thought about getting a 289 a few years ago, but I don't design electronics anymore.

 

[MaxBurn]

I have a dead 8060A and loved it. Can't bring myself to throw it out because I think I might eventually fix it myself or pay to have someone fix it. I was also looking for one at the MIT swap meet but no luck yet.

 

[LunarMist]

I have a dead 8060A and loved it. Can't bring myself to throw it out because I think I might eventually fix it myself or pay to have someone fix it. I was also looking for one at the MIT swap meet but no luck yet.

Can they still be calibrated?

 

[MaxBurn]

And repaired sure. I went so far as to look up schematics and a repair manual for them once.