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#205902 04/22/12 08:49 PM
Joined: Apr 2012
Posts: 2
New Member
Hi All,

I recently moved into a new (to us) home and recently found the voltage at the panel to be too high run some power conditioning devices I have used elsewhere to protect sensitive electronics. We have also experienced a lot of light bulb burn-outs in the 4 weeks we've been here.

ComEd has been out twice now and reports they see nothing above 127 VAC at the outside box, though won't verify if their equipment has ever been calibrated.

I have 4 independent devices, 2 hand-held meters (both in a calibration system) and 2 power conditioning units with displays, that all report 128.5 - 130 VAC.

It's not rational to believe that ALL my devices are out of whack, but ComEd is refusing to discuss further.

What steps can I take to get the power to my house in order? Any advice is appreciated.

Joined: Apr 2002
Posts: 7,382
Likes: 7
My suggestion would be to contact a local electrical contractor. A 'local' guy may have a contact with the POCO who may be able to assist further then what you indicated.

There are basic questions; time of day the voltage readings were taken, load on POCO distribution grid; historical loads; and...meter calibrations, both yours and the POCOs.

What type of Power Conditioning Equipment do you have? Are you sure that the voltage range you state is beyond the range of your devices?

Joined: Jan 2005
Posts: 5,445
Likes: 3
Cat Servant
Even granting that the OP's figures are correct, they are still within the 10% tolerance called for by every standard I can think of. That is, within 10% of the nominal voltage of the distribution system, which would be 120v.

By contrast, even 127v will kill a 120v light bulb pretty fast; the OP needs to purchase bulbs rated for 130v. I suggest he stay away from Home Centers and discount houses.

Joined: Apr 2012
Posts: 2
New Member
Thanks for the quick replies.

To answer a few of the questions:

ComEd tells me 127 VAC is their high limit.

The power conditioners I'm using are made by UltraPower and reading 129 VAC. They indicate that the voltage is "unusable", and are being prevented from operating at all. UltraPower says the units won't operate at voltages greater than 127.

Light bulbs are a pain, but the least of my concerns. I'm transplanting a home music studio into this new house and can't get it powered through the conditioners...which tells me I definitely don't want to plug the studio equipment direct to the wall.

I'm becoming a little concerned about basic appliances as well. How are my kitchen and laundry appliances dealing with this additional current? Are my TVs, stereos and computers going to die premature deaths as well?

Joined: Jul 2004
Posts: 9,931
Likes: 34
I thought it was +5% -10% which squares with the 127 (being a volt too high) thing.

Who is the public utility regulation agency? Maybe see what they have to say.
If you have the calibration certificate for your meter you are probably doing better than the utility.

Greg Fretwell
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
I will begin this Post with a quote from the "Good Book" of ANSI C84.1:

C84.1 Table 1: Standard Nominal System Voltage and Voltage Ranges - 60 Hz.

Voltage Class = Low Voltage (</= 1KV)
Nominal System = 120/240V Three Wire (1 Phase 3 Wire)
Voltage Range(s):

Range "A":

MAXIMUM Utilization & Service Voltage: 126/252V
MINIMUM Service Voltage: 114/228V
MINIMUM Utilization Voltage: 110/220V

Range "B":

MAXIMUM Utilization & Service Voltage: 127/254V
MINIMUM Service Voltage: 110/220V
MINIMUM Utilization Voltage: 106/212V

Range "B" is typical for Power Utility Providers in my areas, and appears to be referenced by the Utility servicing the O.P.

Looking past C84.1 and directly at Nominal Voltage Ratings of given Appliances, Equipment and Lighting Fixtures, the Design specific Working Voltage limits might be "XXX Volts, +/- 10% Maximum Tolerances".

For a given piece of Equipment rated at 120VAC 60 Hz; +/- 10%, this equates to a Maximum Line Input Voltage of 132V, and a Minimum Voltage of 108V.

If the Equipment has an Input Voltage rated at 110VAC; +/- 10%, the Maximum Line Input would be 121V, and the Minimum Line Input Voltage would be 99V

Now for the relevant rated Voltage!

If the Equipment has an Input Voltage rated at 115VAC; +/- 10%, the Maximum Line Input Voltage would be 126.5V, and the Minimum Line Input Voltage would be 103.5V
So far, it appears the Line Conditioners are rated for 115VAC L-N Input Voltage - with 10% Tolerance.

-- Now to look at the Low Voltage Secondary Distribution Feeders --

It is entirely possible, and otherwise normal, for the L-N Voltages observed on the Customer's Side of the KWH Meter / Service Disconnect, to be higher than the L-N Voltage measured at the Transformer's Secondary Bushings (Terminals).
Most common reasons are AC Induction Motors running with very minimal Shaft Load, or no load at all ("Idling").

The Rotors of Unloaded & Lightly loaded Induction Motors will Rotate at or above the Synchronous Frequency of the connected System.
The results of this are a Leading Power Factor, and the Load becomes one of Capacitive Reactance (XC); whereas with a Lagging Power Factor, the Load is one of Inductive Reactance (XL).

Higher XL, or Lagging Power Factors have a resulting increase in Current per the increased level of offset.

Higher XC, or Leading Power Factors have a resulting increase in Voltage per the increased level of offset.

Other culprits responsible for increased Customer Voltage include "Loosely regulated" Electronic Ballasts, Electronic Ballasts not matching the driven Lamps characteristics ("Variety Pack" of various Fluorescent Lamps driven by a certain Ballast), "Noisy" SMPS (Switch Mode Power Supplies) pushing Harmonic VARs back against the Transformer, and similar Non- Linear AC Load Equipment.

A Transient Effect normally occurs when starting an L-N PSC Fan / Blower Motor - except the "Side" of the Secondary which sees the increased Voltage is the "Opposite Side" of the Winding.
A PSC Motor is connected between the "Left End Of The Winding" (refer to as "Line A") and the Center Tapped Neutral. When the Motor is started, the Voltage between the "Right End Of The Winding" (refer to as "Line B") and the Center Tapped Neutral will be slightly elevated.

The increased Voltage will taper down as the Motor increases speed, and balances out when the Motor reaches a stable speed (slipping behind the closest synchronous speed available, allowing the required VA draw to "carry" the needed True Power ((Wattage)) from the Generating Device, in to the Motor's Rotor, and eventually developing a measurable output Horse Power at the Shaft...).

Incandescent Lamp Failures...

Premature failure of Incandescent Lamps is not always an Over Voltage issue...
Excessive Heat, excessive vibration, and "El' Cheapo" Lamps are equivalent Tungsten Filament Killers as well.

When the Incandescent Lamps are operating, how often do they flicker? What are their typical operation characteristics?

If a 130V rated Lamp is undesirable, how about lower Wattage or CFL Counterparts?
Dimmers would keep the initial startup surge issues down, if brought up from maximum dimming, then increased.
If the maximum level is kept below 100% (stop at 95% intensity, so the connected Voltage is less than the Lamp's rated Voltage), the Lamps will operate almost indefinitely.

Voltage tests...

The best method to determine a Voltage Issue is to find the System's Averaged Voltage, per instances.
A Charting Recorder is best here, as each "Event" may be recorded.

Simply stated, the Voltage at the Service Disconnect (KWH Meter) will be lower during peak usage, and higher during off-peak Hours.
The Charting (Recording) type Volt Meter will record Voltage Levels per Time of Day, whenever there is a Sag (decrease in Voltage), or Surge (Increase in Voltage).

When performing a local System analysis, verify the Voltage levels at the Service, while verifying the Voltage levels at a given Equipment Load.
(measure the Service Voltage _AND_ the Voltage at the Load at the same time).
Compare the two readings for verification, so as to determine where the Voltage increase is originating.
Power Quality issues may be generated from your House, your Neighbors, or both.
Power Quality issues on your Neighbors Service may create issues on your Service - and vice verse.

Lastly, "Load" the Circuit being tested prior to using Volt Meters with very high input Impedances.
Use a Linear Resistive device to Load the Circuit - such as a Quartz Halogen Lamp - between 100 and 300 Watts should be fine.
A Portable Heater will also work, but may load the circuit too much!

Simply plug the Lamp (or Heater) in to the same Receptacle being tested. i.e.: Testing a Duplex Receptacle: Plug the Lamp / Heater in to the lower Receptacle, and test through the upper Receptacle.

This should compensate for the Line Charging, which may be affecting a High Input Z Meter.

Personal Story...

The Secondary Distribution Feeder Circuitry, of which my Service is connected to, has a total of (11) Customers connected to it.
The Transformer is 120/240V 1 Phase 3 Wire, 50 KVA, apx. 1.8% Z.
Judging from the way Incandescent Lamps react while Motors are Starting, the %Z should be less than 3% - the Flicker is very minimal, sag level is minimal, and duration is relatively short.

Transformer is 300 Feet away from our Service, and we are the last Service on the Secondary Feeder "String".
Conductors are #4 Copper-Clad Aluminum with type R Insulation.

Approximate Area (Square Footage) of the (11) Dwellings:

(2) at 5,200 Ft. each,
(1) at 3,800 Ft.,
(4) at 3,000 Ft. each,
(4) at 2,600 Ft. each.

All have Swimming Pools, Split System Air Conditioning, Electric Cooking Appliances (Ranges and Ovens), Gas Space and Water Heating.

During peak usage periods, the L-N Voltage at our Computer Room used to sag down as low as 100V. L-L Voltage remained more stable, but ventured down as low as 215V.

Before the 50 KVA Transformer was installed (circa 2000), the previous Transformer was 37.5 KVA, with possibly 5% Z (Incandescent Lamps would have dramatic reactions to AC Motor starts).
Primary Fuse Links were blown at least 10 separate times before the Transformer had a Flash-Over Winding issue.(resulted in +15 Hour Outage!)

Power Quality was crappy before the Troubleshoot replacement of the Barbecued 37.5 KVA Transformer!
To combat this, I installed an Isolation Transformer at the Computer Room, to drive the sensitive Loads - such as Computers, Printers, Monitors, Audio & Video Equipment, as well as other specific Loads.

Transformer has a Tapped Primary Winding (3x 2% FCAN, 3x 2% FCBN), which is rated at 230VAC.
Secondary side contains Dual 120V Shielded Winding Coils, connected in Series and Center Tapped.
Transformer drives a Separate Panelboard, and the complete Assembly is an SDS (Separately Derived System).

BTW, There were a few other Power Quality issues to combat, besides the unstable Voltage from the Transformer.

Time to step down from the Soapbox!

-- Scott (EE)

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Jul 2004
Posts: 9,931
Likes: 34
My line voltage has always been 124/248 + about a half a volt/ - 1 since I have been here. I keep a Weston 901 plugged in all the time to watch it. You can see a little more sag when the HVAC starts.
My Dranitz pretty much confirms that range.
Tripping the main breaker and checking it at the lugs eliminates anything that may be happening at my house. That is within the spec so FPL doesn't really care.

Greg Fretwell
Joined: Apr 2002
Posts: 7,382
Likes: 7
Mi casa runs 118 L-N winter; 110-112 avg in summer with the 4+yr old 50KVA pot & nine neighbors. Similar to Scott SF, and loads.

With old pot (25KVA), brown outs in summer were any day over 85 degrees. It gave it's soul up on a 4th of July weekend. All I can say about that was 'lucky I had a good POCO contact'!!

Joined: Jul 2004
Posts: 9,931
Likes: 34
I guess FPL is doing a great job here but I have believed it for 28 years. The longest outage I have had was Charley and that was about 26 hours. Voltage wise hey have been stable for the whole time.

Greg Fretwell
Joined: Apr 2002
Posts: 7,382
Likes: 7
Not to start a thread jack....but...

I live in an area served by JCP&L, formerly GPU, & JCP&L before that. (First Energy Parent Co)

We have four POCOs, and by public opinion JC wound up dead last for the last 10+/- years. Cost cutting, labor reductions, etc., etc. They are on a major infrastructure upgrade since Irene really put them in hot water again with the State BPU & the Governour.

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